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Subcellular localization of CsTTG1 in epidermal cells of N. benthamiana leaves. (A) Schematic diagram of vectors used for subcellular localization determination. (B) GFP fluorescence was detected 50 h after infiltration. Fluorescence signals were visualized using a fluorescence microscope. Scale bars = 50 μm.
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Plant leaf trichomes are both essential for taxonomy and participate in plant resistance to biotic and abiotic stresses. In the tea plant, teaf trichomes vary significantly among different varieties, ranging from leaves with high trichome density to relatively glabrous leaves. Leaf trichomes provides crucial diagnostic characters for tea identifica...
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Context 1
... determine the subcellular localization of CsTTG1, the coding sequence of CsTTG1 without a termination codon was fused in frame with GFP, and the 35S:CsTTG1-GFP vector was constructed (Fig. 3A). The recombination vector was transformed into Agrobacterium strain GV3101 by the freeze-thaw method. Tobacco Nicotiana benthamiana leaves were infected with Agrobacterium strain GV3101 harbouring the corresponding constructs. The fluorescence signals showed that CsTTG1 was localized in both the cytoplasm and nucleus in the whole cell, ...
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... into Agrobacterium strain GV3101 by the freeze-thaw method. Tobacco Nicotiana benthamiana leaves were infected with Agrobacterium strain GV3101 harbouring the corresponding constructs. The fluorescence signals showed that CsTTG1 was localized in both the cytoplasm and nucleus in the whole cell, and the same result was observed in the control (Fig. ...
Citations
... However, the molecular mechanisms behind the initiation and formation of trichomes and the genetic control of their density in tea remain unclear. TRANSPARENT TESTA GLABRA1 (TTG1) regulates leaf trichome density in tea (Camellia sinensis L.) (Sun et al., 2020). The role of this gene in trichome initiation was reported latter (Hung et al., 2020). ...
One of the best candidates to face the increasing environmental stresses is safflower (Carthamus tinctorius L.) with natural tolerance to multiple abiotic stresses including drought. In the present study, transcriptome profile of a spineless drought‐tolerant mutant of safflower with early flowering was compared to its spiny wild type. In differential RNA‐Seq analyses more than 400 differentially expressed genes (DEGs) were identified in spineless drought‐tolerant mutant. The expression of 8 top DEGs, mostly related to the contrasting traits, was confirmed by real‐time quantitative reverse transcription PCR. Transcription factors (TFs) followed by protein kinases had the highest frequency among the identified DEGs. TF families involved in the regulation of cell cycle, development, and environmental responses were prevalent in DEGs of spineless drought‐tolerant mutant, including NAC, bHLH, MYB, HD‐ZIP, and ERF. Three Kyoto Encyclopedia of Genes and Genomes pathways with direct or indirect role in cell/tissue development and metabolic processes were enriched for DEGs. Our results suggest that phenotypic differences between the two contrasting genotypes can be governed via regulation of hormone signal transduction/or cell cycle and stress‐related pathways. Several candidate genes for spine formation, early flowering, and drought tolerance were introduced, important instances are ZHD8 and TBL21 (candidates for spininess), three novel transcripts, respectively, encoding a CCT type protein, a MADS‐box TF and a CCA1 (candidates for early flowering), and CAT2, ZAT10, and CAMTA (candidates for drought response). These findings facilitate the isolation of key genes controlling drought‐tolerance, spininess, and early flowering in safflower and can be applied for developing value‐added varieties through genome‐based breeding programs.
... In tea plants, at least six CPC-like genes were identified in the tea genome [25] . One CPC genes have been well characterised in trichome formation, which could competitively bind to CsWD40 and CsGL3 to repress CsGL2 expression and tea trichome formation [21] . ...
Tea trichomes contribute significantly to tea flavors by providing diverse and specific flavor-determining metabolites, including catechins,
caffeine, theanine, and volatiles. However, not much is known about the physiological functions of tea trichomes in tea plant adaptation to
complex environments, nor the trichome development. Tea trichomes not only build up chemical defenses, but also act as the first physical
barrier protecting herbivore attacks, reflecting high light and UV-B radiation, and preventing water loss. Moreover, transcriptome profiling on the
tea trichomes compared with the trichome-removed leaves also showed that tea trichomes highly expressed numerous defense-related genes
involved in protection from high light and UV-B radiation, cold stress, disease resistance signal transduction, anti-herbivore or anti-abiotic
peptide biosynthesis, and other defense responses. Several pieces of experimental evidence supported the notes, highlighting the roles of tea
trichomes in plant defenses against both abiotic and biotic stresses. The study provides fresh insights into the multiple protective functions of tea
trichome for tea plant adaptation to harsh environments. The new understanding of tea trichomes could benefit the development of a better
breading strategy for new tea varieties with greater adaption and tolerance to changing environmental challenges.
... The different plant species possessed different numbers of bHLH members, which ranged from 85 to 319 71,72 . Members of the bHLH family were identified in Ginkgo biloba (85) 71 , Solpinganum tuberosum L. (124) 73 , Solanum lycopersicum (159) 74 , Oryza sativa L. (167) 75 , Malus pumila (188) 76 and Glycine max (319) 72 . Twenty-one amino acid residues were conserved in the bHLH domain of tea plants with a consensus rate greater than 50% (Fig. 1), as observed in previous studies 38,77 . ...
... The homologs of CsbHLH024 and CsbHLH133 usually regulate trichome formation by interacting with other TFs in Arabidopsis thaliana. CsTTG1 was involved in tea plant trichome formation, and the overexpression of CsTTG1 could enhance the trichome density of Arabidopsis thaliana 85 ; the functions of other Clusters of Orthologous Groups (COGs) (MYB23, TRY, ETC1, GL1, GL2, SAD2, ETC2 and CPC) in trichome formation were less known in tea plants. CsbHLH024 and CsbHLH133 could interact with CsTTG1 in the heterologous system (Fig. 7B). ...
Leaf trichomes play vital roles in plant resistance and the quality of tea. Basic helix-loop-helix (bHLH) transcription factors (TFs) play an important role in regulating plant development and growth. In this study, a total of 134 CsbHLH proteins were identified in the Camellia sinensis var. sinensis (CSS) genome. They were divided into 17 subgroups according to the Arabidopsis thaliana classification. Phylogenetic tree analysis indicated that members of subgroups IIIc-I and IIIc-II might be associated with trichome formation. The expression patterns of CsbHLH116, CsbHLH133, CsbHLH060, CsbHLH028, CsbHLH024, CsbHLH112 and CsbHLH053 from clusters 1, 3 and 5 were similar to the trichome distribution in tea plants. CsbHLH024 and CsbHLH133 were located in the cell nucleus and possessed transcriptional activation ability. They could interact with CsTTG1, which is a regulator of tea trichome formation. This study provides useful information for further research on the function of CsbHLHs in trichome formation.
... The number of tea trichomes depends on degree of tenderness of tea leaves. The distribution of trichomes is especially thick on newly budded leaves and gradually decreases as the leaf develops [126]. Previous studies had revealed that over 20,000 differentially expressed genes (DEGs) were identified in FDDB (Fudingdabaicha, trichome-rich) and RCZ (Rongchunzao, trichome-less) [127]. ...
Background
Trichomes play a key role in the development of plants and exist in a wide variety of species.
Results
In this paper, it was reviewed that the structure and morphology characteristics of trichomes, alongside the biological functions and classical regulatory mechanisms of trichome development in plants. The environment factors, hormones, transcription factor, non-coding RNA, etc., play important roles in regulating the initialization, branching, growth, and development of trichomes. In addition, it was further investigated the atypical regulation mechanism in a non-model plant, found that regulating the growth and development of tea ( Camellia sinensis ) trichome is mainly affected by hormones and the novel regulation factors.
Conclusions
This review further displayed the complex and differential regulatory networks in trichome initiation and development, provided a reference for basic and applied research on trichomes in plants.
Flavonoids are important compounds in tea leaves imparting bitter and astringent taste, which also play key roles in tea plants responding to environmental stress. Our previous study showed that the expression level of CsMYB67 was positively correlated with the accumulation of flavonoids in tea leaves as exposed to sunlight. Here, we newly reported the function of CsMYB67 in regulating flavonoid biosynthesis in tea leaves. CsMYB67 was localized in the nucleus and responded to temperature. The results of transient expression assays showed the co-transformation of CsMYB67 and CsTTG1 promoted the transcription of CsANS promoter in tobacco system. CsTTG1 was bound to the promoter of CsANS based on the results of yeast one-hybrid (Y1H) and transient expression assays, while CsMYB67 enhanced the transcription of CsANS through protein interaction with CsTTG1 according to the results of yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC). Thus, CsMYB67-CsTTG1 module enhanced the anthocyanin biosynthesis through up-regulating the transcription of CsANS. Besides, CsMYB67 also enhanced the transcription of CsFLS and CsUFGT through forming transcription factor complexes. The function of CsMYB67 on flavonoid biosynthesis in tea leaves was validated by gene suppression assay. As CsMYB67 was suppressed, the transcriptional level of CsFLS was greatly reduced, leading to the significant increase in the contents of total catechins and total anthocyanidins. Hence, CsMYB67 plays an important role in regulating the downstream pathway of flavonoid biosynthesis in summer tea leaves.
Tea plant trichomes not only contribute to the unique flavor and high quality of tea products but also provide physical and biochemical defenses for tea plants. Transcription factors play crucial roles in regulating plant trichome formation. However, limited information about the regulatory mechanism of transcription factors underlying tea plant trichome formation is available. Here, the investigation of trichome phenotypes among 108 cultivars of Yunwu Tribute Tea, integrated with a transcriptomics analysis of both hairy and hairless cultivars, revealed the potential involvement of CsGeBPs in tea trichome formation. In total, six CsGeBPs were identified from the tea plant genome, and their phylogenetic relationships, as well as the structural features of the genes and proteins, were analyzed to further understand their biological functions. The expression analysis of CsGeBPs in different tissues and in response to environmental stresses indicated their potential roles in regulating tea plant development and defense. Moreover, the expression level of CsGeBP4 was closely associated with a high-density trichome phenotype. The silencing of CsGeBP4 via the newly developed virus-induced gene silencing strategy in tea plants inhibited trichome formation, indicating that CsGeBP4 was required for this process. Our results shed light on the molecular regulatory mechanisms of tea trichome formation and provide new candidate target genes for further research. This should lead to an improvement in tea flavor and quality and help in breeding stress-tolerant tea plant cultivars.
Trichomes, which develop from epidermal cells, are considered one of the important characteristics of the tea plant [Camellia sinensis (L.) O. Kuntze]. Many nutritional and metabolomic studies have indicated the important contributions of trichomes to tea products quality. However, understanding the regulation of trichome formation at the molecular level remains elusive in tea plants. Herein, we present a genome-wide comparative transcriptome analysis between the hairless Chuyeqi (CYQ) with fewer trichomes and the hairy Budiaomao (BDM) with more trichomes tea plant genotypes, toward the identification of biological processes and functional gene activities that occur during trichome development. In the present study, trichomes in both cultivars CYQ and BDM were unicellular, unbranched, straight, and soft-structured. The density of trichomes was the highest in the bud and tender leaf periods. Further, using the high-throughput sequencing method, we identified 48,856 unigenes, of which 31,574 were differentially expressed. In an analysis of 208 differentially expressed genes (DEGs) encoding transcription factors (TFs), five may involve in trichome development. In addition, on the basis of the Gene Ontology (GO) annotation and the weighted gene co-expression network analysis (WGCNA) results, we screened several DEGs that may contribute to trichome growth, including 66 DEGs related to plant resistance genes (PRGs), 172 DEGs related to cell wall biosynthesis pathway, 29 DEGs related to cell cycle pathway, and 45 DEGs related to cytoskeleton biosynthesis. Collectively, this study provided high-quality RNA-seq information to improve our understanding of the molecular regulatory mechanism of trichome development and lay a foundation for additional trichome studies in tea plants.
Tea trichomes synthesize numerous specialized metabolites to protect plants from environmental stresses and contribute to tea flavours, but little is known about the regulation of trichome development.
Here, we showed that CsMYB1 is involved in the regulation of trichome formation and galloylated cis‐catechins biosynthesis in tea plants. The variations in CsMYB1 expression levels are closely correlated with trichome indexes and galloylated cis‐catechins contents in tea plant populations. Genome resequencing showed that CsMYB1 may be selected in modern tea cultivars, since a 192‐bp insertion in CsMYB1 promoter was found exclusively in modern tea cultivars but not in the glabrous wild tea Camellia taliensis. Several enhancers in the 192‐bp insertion increased CsMYB1 transcription in modern tea cultivars that coincided with their higher galloylated cis‐catechins contents and trichome indexes.
Biochemical analyses and transgenic data showed that CsMYB1 interacted with CsGL3 and CsWD40 and formed a MYB‐bHLH‐WD40 (MBW) transcriptional complex to activate the trichome regulator genes CsGL2 and CsCPC, and the galloylated cis‐catechins biosynthesis genes anthocyanidin reductase and serine carboxypeptidase‐like 1A. CsMYB1 integratively regulated trichome formation and galloylated cis‐catechins biosynthesis.
Results suggest that CsMYB1, trichome and galloylated cis‐catechins are coincidently selected during tea domestication by harsh environments for improved adaption and by breeders for better tea flavours.
Tea is one of the most consumed beverages worldwide, and trichome formation in tea plant leaves impairs their commercial value. In Arabidopsis thaliana leaves, trichome formation is negatively regulated by the CPC family genes, which encode R3-type MYB transcription factors. Here, we identified six CPC-like genes in a tea plant (Camellia sinensis var. sinensis) for the first time. Simulated three-dimensional structure of the MYB domains of all the six CPC-like proteins exhibited negative charge on the surface, as observed on that of the Arabidopsis CPC protein that does not bind to DNA, indicating their similarity with regard to molecular interaction. We further found that the six CPC-like genes were differentially expressed in different developmental stages of tea leaves, and four out of the six genes were upregulated in the youngest 1st leaves, which formed more trichomes than other older leaves. Although it does not establish a causal link, the correlation between differential expression of CPC-like genes and variable trichome formation suggests that the R3-type MYB transcription factors are potential precipitating factors in affecting the value of tea leaf.
The diversity of trichomes is extremely large in the plant kingdom: this is the pubescence of leaves and glumes in cereals and fruits and petioles in fruit plants, thorns in rose and cucumber, hairs on Drosera leaves, or cotton fibers. Trichomes vary in shape, size, structure, location, capability to secrete, etc. All trichomes share a common basic function—protecting plants from various biotic and abiotic factors. Artificial selection sometimes works against the development of trichomes. For example, in the selection of fruit trees, preference is given to those with smooth fruits. Among wild species, intraspecific variability on the presence/absence of trichomes was also detected. The aim of this review is to compare the mechanisms of formation of trichomes in different species in order to estimate extension of homologous series in hereditary variability within different taxa. Data on the morphology of trichomes are summarized. Data on genes determining variability are compared, and orthologous genes are revealed. Comparison with data on gene networks involved in the development of trichomes indicates that, despite the common molecular mechanisms of trichome development in all higher plants, mutations of different components of this gene network confer observed variability within different taxa.
