ArticlePDF Available

Methyl Jasmonate Application Induces Increased Densities of Glandular Trichomes on Tomato, Lycopersicon esculentum

Authors:
Anthony J Boughton
Anthony J Boughton
Anthony J Boughton
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Kelli Hoover at Pennsylvania State University
Kelli Hoover
Gary W Felton at Pennsylvania State University
Gary W Felton
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

This study was designed to address whether applications of methyl jasmonate (MJ) or Benzothiadiazole (BTH) to cultivated tomato, Lycopersicon esculentum, induced elevated densities of defense-related glandular trichomes on new leaves. Four-leaf tomato plants were sprayed with MJ, BTH, or control solutions, and the density of type VI glandular trichomes on new leaves was subsequently determined at 3, 7, 14, 21, and 28 d. At 7, 14, and 21 d, the density of type VI glandular trichomes on new leaves was significantly higher on MJ-treated plants than on BTH- or control-treated plants. At 7 and 14 d after treatment, the mean density of glandular trichomes on new leaves of MJ-treated plants was ninefold higher than on leaves of control-treated plants. We observed entrapment of immature western flower thrips in trichomes on MJ-treated plants at higher rates than on BTH or control plants. Studies to evaluate potential trade-offs between reductions in pest populations by increased trichome density and possible negative impacts of trichome induction on biological control agents are needed.
Figures - uploaded by Kelli Hoover
Author content
All figure content in this area was uploaded by Kelli Hoover
Content may be subject to copyright.
Content uploaded by Kelli Hoover
Author content
All content in this area was uploaded by Kelli Hoover
Content may be subject to copyright.
RAPID COMMUNICATION
METHYL JASMONATE APPLICATION INDUCES
INCREASED DENSITIES OF GLANDULAR
TRICHOMES ON TOMATO,
Lycopersicon esculentum
ANTHONY J. BOUGHTON,* KELLI HOOVER, and GARY W. FELTON
Department of Entomology, Pennsylvania State University, University Park,
PA 16802, USA
(Received March 21, 2005; revised May 31, 2005; accepted June 2, 2005)
Published Online July 5, 2005
Abstract—This study was designed to address whether applications of methyl
jasmonate (MJ) or Benzothiadiazole (BTH) to cultivated tomato, Lycopersi-
con esculentum, induced elevated densities of defense-related glandular
trichomes on new leaves. Four-leaf tomato plants were sprayed with MJ,
BTH, or control solutions, and the density of type VI glandular trichomes on
new leaves was subsequently determined at 3, 7, 14, 21, and 28 d. At 7, 14,
and 21 d, the density of type VI glandular trichomes on new leaves was
significantly higher on MJ-treated plants than on BTH- or control-treated
plants. At 7 and 14 d after treatment, the mean density of glandular trichomes
on new leaves of MJ-treated plants was ninefold higher than on leaves of
control-treated plants. We observed entrapment of immature western flower
thrips in trichomes on MJ-treated plants at higher rates than on BTH or
control plants. Studies to evaluate potential trade-offs between reductions in
pest populations by increased trichome density and possible negative impacts
of trichome induction on biological control agents are needed.
Key WordsVLycopersicon esculentum, tomato, methyl jasmonate, induced
resistance, glandular trichomes.
0098-0331/05/0900-2211/0
#
2005 Springer Science + Business Media, Inc.
2211
Journal of Chemical Ecology, Vol. 31, No. 9, September 2005 (
#
2005)
DOI: 10.1007/s10886-005-6228-7
* To whom correspondence should be addressed. E-mail: ajb25@psu.edu
INTRODUCTION
Plants have evolved numerous defensive strategies to reduce herbivory or its
effects on plant fitness (Karban and Baldwin, 1997). These defenses may be
constitutively expressed or may be induced following attack by herbivorous
arthropods. Induced responses to herbivory have been widely documented and
may involve changes in plant secondary chemistry, reductions in plant
nutritional quality, emission of volatiles that attract predators and parasitoids
of herbivores (Kessler and Baldwin, 2002), or increases in trichome density
(Traw and Dawson, 2002). Responses to herbivores may be mediated by the
jasmonic acid (JA) or salicylic acid (SA) signaling pathways (Kessler and
Baldwin, 2002).
Trichomes occur on the surfaces of many plants and can make a
contribution to plant resistance against herbivores (Simmons and Gurr, 2004).
Trichomes play important roles in arthropod resistance within the plant family
Solanaceae and particularly within the genus Lycopersicon (Kennedy, 2003).
Seven types of trichomes occur on Lycopersicon spp., including glandular
trichomes (types I, IV, VI, and VII) and nonglandular trichomes (types II, III,
and V) (Luckwill, 1943). Glandular trichomes have heads containing various
sticky and/or toxic exudates that may be secreted onto the plant surface or may
rupture on contact with herbivores, causing irritation, entrapment, or death
(Simmons and Gurr, 2004). Nonglandular trichomes do not have heads and
affect herbivores by mechanically obstructing their movement across the plant
surface (Simmons and Gurr, 2004). Four-lobed type VI glandular trichomes are
associated with high levels of arthropod resistance in L. esculentum (Kennedy,
2003).
Recent studies of the tomato mutant jasmonic acid insensitive 1[jai1],
which is defective in JA-based signaling, revealed several defense-related
phenotypes, including abnormal glandular trichome production, suggesting a
role for JA in glandular trichome-based defenses (Li et al., 2004). JA was
recently shown to induce trichomes in Arabidopsis (Traw and Bergelson,
2003).
To our knowledge, jasmonates have not previously been demonstrated
to induce elevated trichome densities in tomato. In preliminary studies, we
found applications of methyl jasmonate (MJ) and BTH (Actigardi)to
tomato reduced populations of Myzus persicae (Sulzer) (Homoptera: Aphidi-
dae) in the greenhouse (Boughton et al., unpublished data). Here, we
present evidence showing that exogenous application of methyl jasmonate,
but not BTH, induced dramatic increases in densities of type VI glandu-
lar trichomes on new leaves of L. esculentum. We suggest that resistance to
herbivores induced by these elicitors probably operate by different
mechanisms.
2212 BOUGHTON ET AL.
METHODS AND MATERIALS
Plants. Tomato plants (L. esculentum c.v. Trust) (DeRuiter Seeds) were
grown in 4-in. plastic pots in sterile soil mix (peatYperliteYvermiculite,
55Y20Y25; Penn State Seed, Dallas, PA, USA). Plants were grown in the
greenhouse under natural lighting with day and night temperatures varying
between 21 and 33-C. Plants were irrigated daily with fertilizer solution
(NYPYK, 4Y18Y38, Chem-Gro Tomato Formula; Hydro-Gardens Inc., Colorado
Springs, CO, USA) containing supplemental magnesium sulphate and calcium
nitrate.
Effect of Elicitors on Induction of Glandular Trichomes. Fourth-leaf
tomato plants (45 per treatment) selected at random were treated with (1) 7.5
mM MJ (Bedoukian Research, Danbury, CT, USA), or (2) 0.1 mM BTH
(Actigard
\
-Syngenta, Greensboro, NC, USA) (both in 0.8% ethanol and water),
or (3) control solution (0.8% ethanol and water). Elicitor concentrations were
within the range used in other studies and were selected in dose response trials
as the lowest concentrations that induced resistance. Plants receiving different
treatments were moved to opposite sides of the greenhouse and sprayed until
leaves were saturated. After 24 hr, plants were arranged on three benches ac-
cording to a randomized block design. At 3, 7, 14, 21, and 28 days post-
treatment (DPT), three plants from each treatment were selected at random on
each of the three benches, and the youngest terminal leaflet at least 5 cm in
length on each plant was removed for sampling. This leaf selection process
yielded terminal leaflets of similar sizes, which ranged from 5.8 to 8.0 cm
in length, and 11.7 to 21.8 cm
2
in area. Two leaf disks (0.6 cm diam.) were
punched midway between the leaf tip and leaf base, one on either side of the
midrib, taking care to preserve trichomes on the upper leaf surface. Numbers of
FIG. 1. Type VI glandular trichomes on upper surface of leaves from (A) control or (B)
MJ-treated tomato plant at 12 DPT. Photographs show same field of view at 15
magnification.
2213
TRICHOME INDUCTION BY METHYL JASMONATE
type VI trichomes were determined by using a dissecting scope. Preliminary
observations had suggested MJ treatments increase type VI trichome density.
Other trichome types were not examined in this study. Plants were sampled only
once. Trichome density data were evaluated with one-way ANOVA.
RESULTS
Results showed that application of MJ to tomato plants induced increased
densities of type VI glandular trichomes on new leaves expanding after treat-
ment (Figure 1). BTH treatment had no effect on trichome densities (Table 1).
Highest densities of trichomes were present on leaves produced 14 d after
MJ treatment. At 7 and 14 DPT, trichome densities were ninefold higher on
MJ- than control-treated plants. Trichome densities were significantly higher
(Tukey’s test, P < 0.05) on MJ plants than on BTH or control plants at 7, 14 and
21 DPT. MJ-treated plants were observed to entrap higher numbers of im-
mature western flower thrips than BTH- or control-treated plants (Boughton
et al., unpublished data).
DISCUSSION
Increasing interest has focused on the use of elicitors of natural plant
defensive responses, such as JA and MJ, to induce resistance to herbivores and
TABLE 1. EFFECT OF ELICITOR TREATMENT ON GLANDULAR TRICHOME DENSITY ON
NEW TOMATO LEAVES
Mean trichome density
a
(no./mm
2
T SE)
Time point
b
(DPT) Control-treated BTH-treated MJ-treated P value
c
3 0.7 T 0.1 a 0.8 T 0.1 a 0.9 T 0.1 a 0.105
7 1.1 T 0.2 a 1.5 T 0.3 a 9.4 T 0.9 b <0.001
14 2.1 T 0.2 a 2.2 T 0.4 a 17.9 T 1.8 b <0.001
21 3.1 T 0.4 a 3.7 T 0.4 a 12.5 T 1.0 b <0.001
28 5.3 T 0.7 ab 4.7 T 0.6 a 7.2 T 0.5 b 0.027
MJ = Methyl jasmonate, BTH = Benzothiadiazole.
a
Mean density of type VI glandular trichomes on upper surface of new leaves. N = 9 plants per
treatment. One leaf examined per plant. Plants sampled only once. Densities calculated from counts
of trichomes on two leaf disks per leaf. Means within the same row followed by different letters are
significantly different by Tukey’s-test (P < 0.05).
b
Days post-treatment (DPT).
c
One-way ANOVA evaluating effect of treatment on trichome density.
2214 BOUGHTON ET AL.
plant pathogens (Thaler, 1999). In tomato, jasmonate-induced resistance to
herbivores has been documented in several field studies and has frequently been
attributed to the action of defensive proteins such as polyphenol oxidase and
proteinase inhibitors (Thaler, 1999). These proteins are induced within 24 hr of
elicitor treatment, before any changes in type VI trichome density are
detectable. However, over subsequent weeks it seems likely that a component
of jasmonate-induced resistance may be a result of increased densities of type
VI glandular trichomes, contributing to elevated polyphenol oxidase levels and
increased repellency, entrapment, or mortality of arthropod herbivores. We
suggest that elevated trichome densities were likely responsible for increased
thrips entrapment observed in our studies.
Although it is likely that jasmonate-induced resistance in crop plants will
have direct negative impacts on arthropod pests, which may be beneficial from a
pest management perspective, it is also possible that induced plant defenses may
have indirect effects on natural enemies, such as insect parasitoids and pred-
ators, which contribute to the regulation of pest populations (Thaler, 1999;
Simmons and Gurr, 2004). Trichomes, for example, may have differing impacts
on natural enemies ranging from positive effects, such as increased searching
efficiency, to negative effects, such as hindered movement, irritation by tri-
chome exudates, and entrapment (Obrycki, 1986).
The use of jasmonates to induce plant resistance to arthropod pests as a
management tactic will require careful evaluation to ensure that benefits arising
from negative impacts on pest fitness are not outweighed by adverse effects that
might reduce the efficacy of biological control.
AcknowledgmentsVThis research was funded by Pennsylvania Department of Agriculture
(Contract ME 442289).
REFERENCES
K
ARBAN, R. and BALDWIN, I. T. 1997. Induced Responses to Herbivory. University of Chicago
Press, Chicago.
KENNEDY, G. G. 2003. Tomato, pests, parasitoids, and predators: Tritrophic interactions involving
the genus Lycopersicon. Annu. Rev. Entomol. 48:51Y72.
K
ESSLER, A. and BALDWIN, I. T. 2002. Plant responses to insect herbivory: The emerging molecular
analysis. Annu. Rev. Plant Biol. 53:299Y328.
LI, L., ZHAO, Y., MCCAIG, B. C., WINGERD, B. A., WANG, J., WHALON, M. E., PICHERSKY, E., and
H
OWE, G. A. 2004. The tomato homolog of CORONATINE-INSENSITIVE1 is required for
the maternal control of seed maturation, jasmonate-signaled defense responses, and glandu-
lar trichome development. Plant Cell. 16:126Y143.
L
UCKWILL, L. C. 1943. The genus Lycopersicon: A historical, biological and taxonomic survey of
the wild and cultivated tomato. Aberd. Univ. Stud. 120:1Y44.
2215TRICHOME INDUCTION BY METHYL JASMONATE
OBRYCKI, J. J. 1986. The influence of foliar pubescence on entomophagous species, pp. 61Y83, in
D. J. Boethel and R. D. Eikenbarry (eds.). Interactions of Plant Resistance and Parasitoids and
Predators of Insects. Ellis Horwood, Chichester.
S
IMMONS, A. T. and GURR, G. M. 2004. Trichome-based host plant resistance of Lycopersicon
species and the biocontrol agent Mallada signata: are they compatible? Entomol. Exp. Appl.
113:95Y101.
T
HALER, J. S. 1999. Jasmonate-inducible plant defences cause increased parasitism of herbivores.
Nature 399:686Y688.
T
RAW, M. B. and BERGELSON, J. 2003. Interactive effects of jasmonic acid, salicylic acid, and
gibberellin on induction of trichomes in Arabidopsis. Plant Physiol. 133:1367Y1375.
TRAW, M. B. and DAWSON, T. E. 2002. Reduced performance of two specialist herbivores
(Lepidoptera: Pieridae, Coleoptera: Chrysomelidae) on new leaves of damaged black mustard
plants. Environ. Entomol. 31:714Y722.
2216 BOUGHTON ET AL.
... Studies have shown that knocking out the HD-ZIP IV transcription factor (TF) wool (wo) resulted in significant defects in trichomes and reduced terpene levels, and was associated with insect resistance in tomatoes [30]. Me-JA induces the formation of type VI glandular trichomes in newly expanded tomato leaves, thereby reducing herbivorous insect populations [31]. The gene regulatory network controlling trichome development is complex [32]. ...
... In the future, it will be worthwhile to investigate which secondary metabolites are induced after UFW treatment. JA is known to be involved in trichome development [30,31]. In this study, we found that the trichome initiation marker gene GL2 was significantly upregulated in young leaves after UF+H 2 treatment ( Figure 4E), further supporting that hydrogen may induce JA and enhance trichome initiation to prevent herbivory. ...
Safe Farming: Ultra-Fine Sparkling Water can Reduce Insect Pests and Increase Melon Yield and Quality
Article
  • Jan 2024
Melon pest control relies on over-application of pesticides. Reducing pesticide spraying has become a global issue for environmental sustainability and human health. Therefore, it is important to develop a new growing system that is sustainable and environmentally friendly. This study found that melon seedlings irrigated with ultrafine water containing H2 and O2 (UFW) produced more root hairs, increased branch height, and produced more flowers than the control irrigated with reverse osmosis (RO) water. Surprisingly, we also found that UFW irrigation significantly reduced aphid infestations in melons. Based on cryoscanning electron microscopy (cryo-SEM) observations, UFW treatment enhanced trichome development and prevented aphid infestation. To investigate whether it was H2 or O2 to prevent insect damage, we prepared UF enriched water with H2 (UF+H2 ) and O2 (UF+O2 ) alone and irrigated the melons. Cryo-SEM results show that UF+H2 and UF+O2 can increase the density of trichomes in melon leaves and petioles. RT-qPCR showed that UF+H2 significantly increased the gene expression level of the trichome-related gene GLABRA2 (GL2). We grow muskmelons in plastic greenhouses and use ultrafine water-rich hydrogen (UF+H2 ) and oxygen (UF+O2 ). The SPAD value, photosynthetic parameters, root weight, fruit weight, and fruit sweetness are all better than those without ultrafine water irrigation of comparison. UFW significantly promoted the development of trichomes, enhanced insect resistance, and improved fruit traits. The system therefore provides useful water management for pest control and sustainable agricultural production.
View
... Research showed that the knockout of an HD-ZIP IV transcription factor (TF), woolly (wo), led to a significant defect in trichomes and a reduction of terpene levels and is associated with insect resistance in tomatoes [30]. Me-JA induced type VI glandular trichome formation on the newly expanding tomato leaves, thus decreasing herbivore insect populations [31]. The gene regulation network controlling trichome development is complex [32]. ...
... JA is known to be involved in trichome development [30,31]. In this study, we found that a trichome initiation marker gene GL2 was significantly upregulated in young leaves after UF+H 2 treatment ( Figure 4E), further supporting the notion that hydrogen may induce JA and enhance trichome initiation to prevent herbivory infestation and improve plant growth. ...
Safe Farming: Ultrafine Bubble Water Reduces Insect Infestation and Improves Melon Yield and Quality
Article
Full-text available
  • Feb 2024
Melon pest management relies on the excessive application of pesticides. Reducing pesticide spraying has become a global issue for environmental sustainability and human health. Therefore, developing a new cropping system that is sustainable and eco-friendly is important. This study found that melon seedlings irrigated with ultrafine water containing H2 and O2 (UFW) produced more root hairs, increased shoot height, and produced more flowers than the control irrigated with reverse osmosis (RO) water. Surprisingly, we also discovered that UFW irrigation significantly reduced aphid infestation in melons. Based on cryo-scanning electron microscope (cryo-SEM) observations, UFW treatment enhanced trichome development and prevented aphid infestation. To investigate whether it was H2 or O2 that helped to deter insect infestation, we prepared UF water enrichment of H2 (UF+H2) and O2 (UF+O2) separately and irrigated melons. Cryo-SEM results indicated that both UF+H2 and UF+O2 can increase the density of trichomes in melon leaves and petioles. RT-qPCR showed that UF+H2 significantly increased the gene expression level of the trichome-related gene GLABRA2 (GL2). We planted melons in a plastic greenhouse and irrigated them with ultrafine water enrichment of hydrogen (UF+H2) and oxygen (UF+O2). The SPAD value, photosynthetic parameters, root weight, fruit weight, and fruit sweetness were all better than the control without ultrafine water irrigation. UFW significantly increased trichome development, enhanced insect resistance, and improved fruit traits. This system thus provides useful water management for pest control and sustainable agricultural production.
View
... In wild potato relatives, higher densities of glandular trichomes were associated with reduced oviposition by a lepidopteran herbivore (Horgan et al., 2009). Likewise, in tomato, increased glandular trichome density was associated with higher rates of entrapment of western flower thrips (Boughton et al., 2005), and removal of glandular trichomes of many chenopod species led to increased herbivory (LoPresti, 2014). The identification of genes involved in the development of glandular trichomes and in the biosynthesis of metabolites that may be responsible for their resistance functions has led to increased interest in these structures as targets for breeding resistance to pests (Glas et al., 2012). ...
... Within populations, there is heritable variation in trichome density (Ågren and Schemske, 1992). Within genotypes, trichome density can vary based on ontogeny (Xing et al., 2017), abiotic conditions (Dalin et al., 2008), induction by herbivores (Tian et al., 2012), and the levels of plant hormones (Boughton et al., 2005). In some cases, trichome density is positively correlated with overall plant vigor (i.e., size, health, or growth rate of a plant; Chakraborty, 2021), but not in other cases (Haber et al., 2018). ...
The evolution of glandularity as a defense against herbivores in the tarweed clade
Article
Full-text available
  • Feb 2024
  • AM J BOT
Premise Glandular trichomes are implicated in direct and indirect defense of plants. However, the degree to which glandular and non‐glandular trichomes have evolved as a consequence of herbivory remains unclear, because their heritability, their association with herbivore resistance, their trade‐offs with one another, and their association with other functions are rarely quantified. Methods We conducted a phylogenetic comparison of trichomes and herbivore resistance against the generalist caterpillar, Heliothis virescens , among tarweed species (Asteraceae: Madiinae) and a genetic correlation study comparing those same traits among maternal half‐sibs of three tarweed species. Results Within a tarweed species, we found no evidence that herbivore growth rate decreased on tarweed individuals or maternal sib groups with more glandularity or denser trichomes. However, tarweed species with more glandularity and fewer non‐glandular trichomes resulted in slower‐growing herbivores. Likewise, a trade‐off between glandular and non‐glandular trichomes was apparent among tarweed species, but not among individuals or sib groups within a species. Conclusions Our results suggest that this key herbivore does not select for trichomes as a direct defense in tarweed species. However, trichomes differed substantially among species and likely affect herbivore pressure on those species. Our results demonstrate that trade‐offs among plant traits, as well as inference on the function of those traits, can depend on scale.
View
... Research showed that the knockout of an HD-ZIP IV transcription factor (TF), woolly (wo), led to a significant defect in trichomes and a reduction of terpene levels and is associated with insect resistance in tomatoes [30]. Me-JA induced type VI glandular trichome formation on the newly expanding tomato leaves, thus decreasing herbivore insect populations [31]. The gene regulation network controlling trichome development is complex [32]. ...
... JA is known to be involved in trichome development [30,31]. In this study, we found that a trichome initiation marker gene GL2 was significantly upregulated in young leaves after UF+H2 treatment ( Figure 4E), further supporting the notion that hydrogen may induce JA and enhance trichome initiation to prevent herbivory infestation and improve plant growth. ...
Safe Farming: Ultrafine Bubble Water Induces Trichomes to Prevent Insect Damage and Improves Melon Yield and Quality
Preprint
Full-text available
  • Dec 2023
Melon pest management relies on the excessive application of pesticides. Reducing pesticide spraying has become a global issue for environmental sustainability and human health. Therefore, developing a new cropping system that is sustainable and eco-friendly is important. This study found that melon seedlings irrigated with ultrafine water containing H2 and O2 (UFW) produced more root hairs, increased shoot height, and produced more flowers than the control irrigated with reverse osmosis (RO) water. Surprisingly, we also discovered that UFW irrigation significantly reduced aphid infestation in melon. Based on cryo-scanning electron microscope (cryo-SEM) observations, UFW treatment enhanced trichome development and prevented aphid infestation. To investigate whether it was H2 or O2 that helped to deter insect infestation, we prepared UF water enrichment of H2 (UF+H2) and O2 (UF+O2) separately and irrigated melons. Cryo-SEM results indicated that both UF+H2 and UF+O2 can increase the density of trichomes in melon leaves and petioles. RT-qPCR showed that UF+H2 significantly increased the gene expression level of the trichome-related gene GLABRA2 (GL2). We planted melons in a plastic greenhouse and irrigated them with ultrafine water enrichment of hydrogen (UF+H2) and oxygen (UF+O2). The SPAD value, photosynthetic parameters, root weight, fruit weight, and fruit sweetness were all better than the control without ultrafine water irrigation. UFW significantly increased trichome development, enhanced insect resistance, and improved fruit traits. This system thus provides useful water management for pest control and sustainable agricultural production.
View
... Glandular trichomes on the other hand, synthesize and secrete defensive compounds to protect against herbivores (Weinhold and Baldwin 2011;Bleeker et al. 2012;Sasse et al. 2016). Moreover, many plant species increase trichome formation in response to herbivore attack, mechanical damage, or phytohormone treatment (Agrawal 1999;Brian Traw and Dawson 2002;Dalin and Björkman 2003;Boughton et al. 2005;Zhang et al. 2019). In cucurbit plants, the profile and density of trichomes vary depending on the species and the purpose of domestication. ...
Cultivar-Specific Defense Responses in Wild and Cultivated Squash Induced by Belowground and Aboveground Herbivory
Article
Full-text available
  • Jun 2024
  • J CHEM ECOL
Plant domestication often alters plant traits, including chemical and physical defenses against herbivores. In squash, domestication leads to reduced levels of cucurbitacins and leaf trichomes, influencing interactions with insects. However, the impact of domestication on inducible defenses in squash remains poorly understood. Here, we investigated the chemical and physical defensive traits of wild and domesticated squash (Cucurbita argyrosperma), and compared their responses to belowground and aboveground infestation by the root-feeding larvae and the leaf-chewing adults of the banded cucumber beetle Diabrotica balteata (Coleoptera: Chrysomelidae). Wild populations contained cucurbitacins in roots and cotyledons but not in leaves, whereas domesticated varieties lacked cucurbitacins in all tissues. Belowground infestation by D. balteata larvae did not increase cucurbitacin levels in the roots but triggered the expression of cucurbitacin biosynthetic genes, irrespective of domestication status, although the response varied among different varieties. Conversely, whereas wild squash had more leaf trichomes than domesticated varieties, the induction of leaf trichomes in response to herbivory was greater in domesticated plants. Leaf herbivory varied among varieties but there was a trend of higher leaf damage on wild squash than domesticated varieties. Overall, squash plants responded to both belowground and aboveground herbivory by activating chemical defense-associated gene expression in roots and upregulating their physical defense in leaves, respectively. While domestication suppressed both chemical and physical defenses, our findings suggest that it may enhance inducible defense mechanisms by increasing trichome induction in response to herbivory.
View
... Caterpillars feeding JA-deficient tomato mutants exhibit higher survivorship and weight gain than wild-type plants [49,53]. Exogenous application of JA or methyl jasmonate (MeJA) boosts plant resistance to herbivores and stimulates defensive protein expression in tomatoes [54][55][56][57][58]. This highlights JA's pivotal role in regulating plant defences against herbivores, with a JA-mediated pathway identified from insect attack to defensive gene expression in plants [39,47,[59][60][61]. ...
Genome-Wide Transcriptomic and Metabolomic Analyses Unveiling the Defence Mechanisms of Populus tremula against Sucking and Chewing Insect Herbivores
Article
Full-text available
  • Jun 2024
  • INT J MOL SCI
Plants and insects coevolved as an evolutionarily successful and enduring association. The molecular arms race led to evolutionary novelties regarding unique mechanisms of defence and detoxification in plants and insects. While insects adopt mechanisms to conquer host defence, trees develop well-orchestrated and species-specific defence strategies against insect herbivory. However, current knowledge on the molecular underpinnings of fine-tuned tree defence responses against different herbivore insects is still restricted. In the current study, using a multi-omics approach, we unveiled the defence response of Populus tremula against aphids (Chaitophorus populialbae) and spongy moths (Lymantria dispar) herbivory. Comparative differential gene expression (DGE) analyses revealed that around 272 and 1203 transcripts were differentially regulated in P. tremula after moth and aphid herbivory compared to uninfested controls. Interestingly, 5716 transcripts were differentially regulated in P. tremula between aphids and moth infestation. Further investigation showed that defence-related stress hormones and their lipid precursors, transcription factors, and signalling molecules were over-expressed, whereas the growth-related counterparts were suppressed in P. tremula after aphid and moth herbivory. Metabolomics analysis documented that around 37% of all significantly abundant metabolites were associated with biochemical pathways related to tree growth and defence. However, the metabolic profiles of aphid and moth-fed trees were quite distinct, indicating species-specific response optimization. After identifying the suitable reference genes in P. tremula, the omics data were further validated using RT-qPCR. Nevertheless, our findings documented species-specific fine-tuning of the defence response of P. tremula, showing conservation on resource allocation for defence overgrowth under aphid and moth herbivory. Such findings can be exploited to enhance our current understanding of molecular orchestration of tree responses against herbivory and aid in developing insect pest resistance P. tremula varieties.
View
Essential Oils’ Biosynthesis and their Application
Chapter
  • Apr 2024
Aromatherapy is a medical practice that uses aromatic compounds or essential oils to influence mood and health. Essential oils used in aromatherapy are created from a wide variety of medicinal plants, flowers, herbs, roots, and trees that are found all over the world and have significant, well-documented benefits on enhancing physical, emotional, and spiritual wellbeing. This book is a comprehensive reference on aromatic compounds present in essential oils and their therapeutic use. Starting from fundamentals of essential oil biosynthesis the book guides the reader through their basic biochemistry, toxicology, profiling, blending and clinical applications. The concluding chapters also present focused information about the therapeutic effects of essential oils on specific physiological systems, plant sources, skin treatment and cancer therapeutics. The combination of basic and applied knowledge will provide readers with all the necessary information for understanding how to develop preclinical formulations and standard clinical therapies with essential oils. This is an essential reference for anyone interested in aromatherapy and the science of essential oils.
View
View
Recent Invasive Sucking Pests and their Management
Chapter
Full-text available
  • Nov 2023
Invasive alien species (IAS) refer to foreign organisms that establish themselves in natural or semi-natural ecosystems, causing disruption and endangering indigenous biodiversity. In India, invasive insects pose significant threats to homes, agriculture, human well-being and the environment. India's diverse climate fosters the introduction and adaptation of various insects from different regions. Globalization has further expedited the influx of invasive insect pests. Presently, India has recorded 23 invasive alien insect species, with four of them being recent additions categorized as sucking pests. This chapter exclusively addresses the traits that render insects invasive, their common entry routes, the stages of establishment, morphological identification, host plants, damaging symptoms and effective management strategies.
View
Heat stress induces a developmental shift from type-V to type-IV trichome dependent on jasmonate signaling in tomato
Preprint
Full-text available
  • Jul 2023
Cultivated tomato (Solanum lycopersicum) and related wild species develop several types of trichomes, both glandular and non-glandular, on their aerial parts. Among these, type-IV trichomes are responsible for the synthesis and secretion of acylsugars, which act as defense compounds against herbivores. In contrast to related wild species such as S. pennellii, type-IV trichomes are present only in the juvenile stages of cultivated tomato plants and absent in later stages of development. By submitting tomato plants to high temperatures during the day (37 {degree sign}C), we observe that non-glandular type-V trichomes are replaced by type-IV trichomes. This is accompanied by a massive increase in acylsugar production. On the other hand, heat treatment does not affect type VI-trichomes, which produce mono- and sesquiterpenes, but the production of monoterpenes is increased while that of sesquiterpenes is suppressed. Furthermore, tomato jai1 mutants deficient in jasmonate (JA) perception do not exhibit this developmental switch from type-V to type-IV trichomes. The implication of JA signaling in this process was further supported by an increase in JA-isoleucine and in the expression of genes involved in JA-signalling within hours of heat stress application. These results establish a unique system to study how environmental factors affect developmental fate decisions in plants while opening opportunities to understand mechanisms controlling type-IV trichome initiation and development.
View
Reduced Performance of Two Specialist Herbivores (Lepidoptera: Pieridae, Coleoptera: Chrysomelidae) on New Leaves of Damaged Black Mustard Plants
Article
Full-text available
  • Aug 2002
  • ENVIRON ENTOMOL
This study addressed whether prior damage to black mustard, Brassica nigra (L.) Koch, would reduce growth, herbivory, or mortality of two specialist herbivores on new leaves. Plants received either no initial damage or 12 h of feeding by two third instars of Pieris rapae (L.) or 50 adult Phyllotreta cruciferae (Goeze) when plants had four leaves. Later, the seventh leaf of plants was either harvested for measurement of trichome density and glucosinolate concentration or enclosed in a mesh cage containing two neonate P. rapae or 10 adult P. cruciferae. Caged herbivores were measured for mass gain, leaf consumption, and mortality after 1 wk. Damage by P. rapae caused substantial increases in trichome density and sinigrin concentration, whereas damage by P. cruciferae had no effect. Larvae of P. rapae grew 30% more slowly on plants initially damaged by conspecifics than on control plants. Percent herbivory by P. rapae was 33% lower on plants initially damaged by either P. rapae or P. cruciferae than on control plants. Growth rate and percent herbivory by P. cruciferae were not generally affected by prior plant damage. However, mortality of P. cruciferae was 84% higher on plants previously damaged by conspecifics than on control plants. Together, the data demonstrate that induction responses negatively affected both Pieris and Phyllotreta and suggest that trichomes may be relatively important in the increased resistance. Test herbivores generally performed similarly on plants damaged by either herbivore, suggesting a low specificity of effect for the induction response.
View
Tomato, Pests, Parasitoids, and Predators: Tritrophic Interactions Involving the Genus Lycopersicon
Article
Full-text available
  • Feb 2003
Insect-plant interactions involving the cultivated tomato and its relatives in the genus Lycopersicon have been intensively studied for several decades, resulting in one of the best documented and in-depth examples of the mechanistic complexities of insect-plant interactions, which encompass both herbivores and their natural enemies. Trichome-mediated defenses are particularly significant in L. hirsutum f. glabratum and have been extensively implicated in negative tritrophic effects mediated by direct contact of parasitoids and predators with trichomes, as well as indirect effects mediated through their hosts or prey. Both constitutive and inducible defense traits of L. esculentum exert effects on selected parasitoids and predators. The effects of any particular plant defense trait on parasitoids and predators depend on the specific attributes of the plant trait and the details of the physical, biochemical, and behavioral interaction between the natural enemy, its host (prey), and the plant.
View
Kessler, A. & Baldwin, I. T. Plant responses to insect herbivory: the emerging molecular analysis. Annu. Rev. Plant Biol. 53, 299-328
Article
Full-text available
  • Feb 2002
Plants respond to herbivore attack with a bewildering array of responses, broadly categorized as direct and indirect defenses, and tolerance. Plant-herbivore interactions are played out on spatial scales that include the cellular responses, well-studied in plant-pathogen interactions, as well as responses that function at whole-plant and community levels. The plant's wound response plays a central role but is frequently altered by insect-specific elicitors, giving plants the potential to optimize their defenses. In this review, we emphasize studies that advance the molecular understanding of elicited direct and indirect defenses and include verifications with insect bioassays. Large-scale transcriptional changes accompany insect-induced resistance, which is organized into specific temporal and spatial patterns and points to the existence of herbivore-specific trans-activating elements orchestrating the responses. Such organizational elements could help elucidate the molecular control over the diversity of responses elicited by herbivore attack.
View
Interactive Effects of Jasmonic Acid, Salicylic Acid, and Gibberellin on Induction of Trichomes in Arabidopsis
Article
Full-text available
  • Dec 2003
  • PLANT PHYSIOL
Leaf trichomes protect plants from attack by insect herbivores and are often induced following damage. Hormonal regulation of this plant induction response has not been previously studied. In a series of experiments, we addressed the effects of artificial damage, jasmonic acid, salicylic acid, and gibberellin on induction of trichomes in Arabidopsis. Artificial damage and jasmonic acid caused significant increases in trichome production of leaves. The jar1-1 mutant exhibited normal trichome induction following treatment with jasmonic acid, suggesting that adenylation of jasmonic acid is not necessary. Salicylic acid had a negative effect on trichome production and consistently reduced the effect of jasmonic acid, suggesting negative cross-talk between the jasmonate and salicylate-dependent defense pathways. Interestingly, the effect of salicylic acid persisted in the nim1-1 mutant, suggesting that the Npr1/Nim1 gene is not downstream of salicylic acid in the negative regulation of trichome production. Last, we found that gibberellin and jasmonic acid had a synergistic effect on the induction of trichomes, suggesting important interactions between these two compounds.
View
The tomato homolog of CORONATINE-INSENSITIVE1 is required for the maternal control of seed maturation, jasmonate-signaled defense responses, and glandular trichome development
Article
Full-text available
  • Feb 2004
Jasmonic acid (JA) is a fatty acid-derived signaling molecule that regulates a broad range of plant defense responses against herbivores and some microbial pathogens. Molecular genetic studies in Arabidopsis have established that JA also performs a critical role in anther and pollen development but is not essential for other developmental aspects of the plant's life cycle. Here, we describe the phenotypic and molecular characterization of a sterile mutant of tomato (jasmonic acid-insensitive1 [jai1]) that is defective in JA signaling. Although the mutant exhibited reduced pollen viability, sterility was caused by a defect in the maternal control of seed maturation, which was associated with the loss of accumulation of JA-regulated proteinase inhibitor proteins in reproductive tissues. jai1 plants exhibited several defense-related phenotypes, including the inability to express JA-responsive genes, severely compromised resistance to two-spotted spider mites, and abnormal development of glandular trichomes. We demonstrate that these defects are caused by the loss of function of the tomato homolog of CORONATINE-INSENSITIVE1 (COI1), an F-box protein that is required for JA-signaled processes in Arabidopsis. These findings indicate that the JA/COI1 signaling pathway regulates distinct developmental processes in different plants and suggest a role for JA in the promotion of glandular trichome-based defenses.
View
View
Jasmonate-inducible plant defences cause increased parasitism of herbivores
Article
  • Jun 1999
  • NATURE
In many plants, defence systems against herbivores are induced through the octadecanoid pathway,, which may also be involved in recruiting natural enemies of herbivores. This pathway can beinduced by treating plants with jasmonic acid or by natural herbivory, and increases resistance against herbivorous insects intomato plants, in part by causing production of toxic and antinutritive proteinase inhibitors and oxidative enzymes. Herbivore-infested tomato plants release increased amounts of volatiles and attract natural enemies of the herbivores, as do other plants. The octadecanoid pathway may regulate production of these volatiles, which attract host-seeking parasitic wasps,. However, plant resistance compounds can adversely affect parasitoids as well as herbivores. It is unclear whether the combination of increased retention and/or attractiveness of parasitic wasps to induced plants and the adverse effects of plant defence compounds on both caterpillars and parasitoids results in a net increase in parasitization of herbivores feeding on induced plants.Here I show that inducing plants with jasmonic acid increases parasitism of caterpillar pests in an agricultural field twofold. Thus, elicitors of plant resistance may become useful in agriculture.
View
Trichome-based host plant resistance of Lycopersicon species and the biocontrol agent Mallada signata: Are they compatible?
Article
  • Nov 2004
  • ENTOMOL EXP APPL
Trichome-based host plant resistance of Lycopersicon (Solanaceae) species offers the potential to reduce pesticide use in tomato production, but its compatibility with biocontrol agents is largely unknown. The effect of trichome-based host plant resistance on the lacewing biocontrol agent, Mallada signata, was assessed for five accessions of L. cheesmanii, four accessions of Lycopersicon hirsutum, two accessions of Lycopersicon pennellii, and one Lycopersicon esculentum cultivar. An intact leaf was isolated from the whole plant using Tangletrap to coat the petiole and 20 green peach aphids [Myzus persicae (Sulzer) (Homoptera: Aphididae)] were placed on the leaf surface. After 24 h, 10 lacewings were placed on the leaf. The numbers of dead, trapped by exudates, untrapped and predated lacewings and aphids, and the numbers that had left the leaf were recorded a further 24 h later. Differences in insect designations between accessions were analysed using ANOVA. A General Linear Model (GLM), consisting of the densities of each trichome type and leaf area, was fitted to the data to determine the role of trichomes on the observed effects on lacewings and aphids. Lacewing mortality was greater on one accession of L. pennellii and one accession of L. hirsutum than on L. esculentum. The GLM indicated that type IV trichomes decreased the numbers of aphids predated, and increased cannibalism and, along with type III trichomes, increased entrapment-related predator mortality. Although there were no differences in the numbers of predated aphids, with the majority predated for all accessions, the compatibility of trichome-based host plant resistance of Lycopersicon species and the biocontrol of aphids by lacewings is questionable.
View
Induced Response to Herbivory
Article
  • Jan 1999
Plants face a daunting array of creatures that eat them, bore into them, and otherwise use virtually every plant part for food, shelter, or both. But although plants cannot flee from their attackers, they are far from defenseless. In addition to adaptations like thorns, which may be produced in response to attack, plants actively alter their chemistry and physiology in response to damage. For instance, young potato plant leaves being eaten by potato beetles respond by producing chemicals that inhibit beetle digestive enzymes. Over the past fifteen years, research on these induced responses to herbivory has flourished, and here Richard Karban and Ian T. Baldwin present the first comprehensive evaluation and synthesis of this rapidly developing field. They provide state-of-the-discipline reviews and highlight areas where new research will be most productive. Their comprehensive overview will be welcomed by a wide variety of theoretical and applied researchers in ecology, evolutionary biology, plant biology, entomology, and agriculture.
View
Plant responses to insect herbivory: The emerging molecular analysis
  • Jan 2002
  • 299-328
KESSLER, A. and BALDWIN, I. T. 2002. Plant responses to insect herbivory: The emerging molecular analysis. Annu. Rev. Plant Biol. 53:299Y328.