Seed transmitted beneficial endophytic Stagonospora sp. can penetrate the walls of the root epidermis, but does not proliferate in the cortex of Phragmites australis
Abstract and Figures
Stagonospora sp. (4/99-1) is a beneficial endophytic fungus frequently transmitted by seeds of Phragmites australis[Cav.] Trin. ex Steudel. Here we show that this fungus also penetrates the root epidermis. At first, hyphae were attracted by the root and proliferated on the root surface, preferably over the anticlinal walls. Penetration occurred directly by undifferentiated hyphae or was facilitated by hyphopodia. Hyphal growth within the root was restricted to the walls of epidermal cells and the walls of the cells of the outermost cortical layer. Deeper growth by the fungus elicited wall appositions and ingress into the cytoplasm of cortical cells was blocked by papillae. In the rare cases the fungus managed to penetrate into cortical cells, these reacted with necrosis. Immunological studies suggested that fungal material reached the host plasmalemma and may have been taken up by endocytotic events. Our observations explain the endophytic lifestyle of hyphae close to the epidermis and the restricted development within the cortex.
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... Endophytes are important components of plant microbiomes, as microbes that live within plant tissues without causing symptoms of disease [2]. Endophytes usually come from the vertical transmission of host seeds and the horizontal transmission of air and soil microorganisms [3][4][5]. In the symbiotic relationship, the plant helps endophytes by providing nutrients and shelter, while endophytes can produce plant hormones, change antioxidant enzymes activity and promote growth of host plants under stress conditions [6,7]. ...
... Immunofluorescence labeling: The preparation of pre-adsorption to remove antibodies recognizing unspecific epitopes and primary antibody was carried out according to the method of Ernst [3]. The mycelial powders used for the pre-adsorption were generated from Botryosphaeria ribis strains YL-JJ, Rhizoctonia solani strains Rs-1, R. solani strains Rs, Pythium aphanidermatum strains Pa, and Fusarium oxysporium strains F, which were prepared according to the method of Gao and Mendgen [4]. According to the amended method of Kang [34], immunofluorescence labeling was carried out as follows: after inoculation for 8 h and 12 h, samples were submerged in fixed transparent liquid (chloroform: dehydrated alcohol = 1: 4, and 0.15 g trichloroacetic acid added in 100 mL) for 12 h at 4 • C, then transferred to chloral hydrate for 1 h, washed twice with 50% dehydrated alcohol, 15 min per times, then rinsed 3 times with sterile demineralized water, blocked in 1% (w/v) bovine serum albumin in PBS (pH 7.2) for 30 min and washed 3 times with PBS, then incubated in primary antibody diluted 1:100 in PBS for 1 h, and rinsed 6 times with PBS, 5 min per times, then treated with goat anti-rabbit IgG-FITC (Solarbio, Beijing, China) diluted 1:10 in PBS for 1 h, and rinsed 6 times with PBS, 5 min per time, then washed for 1 min with sterile demineralized water, subsequently immersed in 50% dehydrated alcohol. ...
... Resin Embedding and Transmission Electron Microscopy: The cucumber radicles at 36 hpi, 48 hpi and 60 hpi were treated using the method of Gao and Mendgen [4]. Root samples were fixed in 2.5% glutaraldehyde in 0.1 M cacodylate buffer at pH 7.4 with 1 mm CaCl and 1% (w/v) sucrose for 3 h at room temperature, and postfixed with 1% (w/v) osmium tetroxide in the same buffer for 2 h at room temperature. ...
Endophytic fungi are effective in plant growth and development by secreting various kinds of plant hormones and nutrients. However, the cellular and molecular interactions between the endophytic fungi and plant growth-promoting have remained less explored. The present study was designed to explore the effects of the infection and colonization events of Chaetomium globosum strain ND35 on cucumber growth and the expression pattern of some metabolically important genes in development of the cucumber radicle. The results demonstrated that strain ND35 can infect and colonize the outer layers (cortical cells) of cucumber root and form a symbiotic structure with the host cell, similar to a periarbuscular membrane and establish chemical communication with the plant. Through transcriptome analysis, we found the differentially expressed genes (DEGs) caused by strain ND35 were mainly enriched in phenylpropanoid biosynthesis, plant hormone signal transduction, plant-pathogen interaction and photosynthesis. Correspondingly, the contents of reactive oxygen species (ROS), hydrogen peroxide (H2O2), indole-3-acetic acid (IAA), gibberellin (GA), zeatin (ZT), salicylic acid (SA), jasmonic acid (JA) and the activity of phenylalanine ammonia lyase (PAL), 4-coumarate-CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) in ND35-colonized seedlings were generally higher than those of non-inoculated seedlings. Overall, the infection and colonization events of C. globosum strain ND35 increased cucumber growth through complex regulation of plant hormones biosynthesis and metabolism. Furthermore, although the endophytic fungus strain ND35 produced IAA, GA, ZT, and ergosterol in the fermentation broth, and there are enabled to promote growth of cucumber, it is uncertain whether there are ND35-derived microbial hormones in plants. This study of the interaction between cucumber and strain ND35 contributes to a better understanding of the plant-endophytic fungi interactions, and may help to develop new strategies for crop production.
... But contrary to the dark septate endophytes in P. oceanica roots, endophytes in this study reached and densely colonized the cortical cells (Vohnik et al. 2017 In this study, absence of hyphal colonization in the vascular tissues of seagrasses suggested non-systemic fungal colonization. According to Gao and Mendgen, 2006, the growth of endophytic fungi is maintained and restricted in de ned areas of the plant tissues by the hosts' defense reaction. For instance, cell wall and membrane are strengthened and plant innate immune responses are activated resulting to reactive oxygen species generation; defense genes expression and hormones synthesis (Gebrei 2016). ...
Endophytic fungal colonization in plants is governed by complex interactions with the defense mechanism of the host and antagonistic effects of other endophytes. In this study, endophytic fungal interaction was assessed by histological examination and co-culture methods. Results showed fungal colonization in the intercellular space of the epidermis and both intercellular and intracellular spaces of the cortical cells suggesting close interaction with their seagrass hosts. Dense colonization, hyphal branching, coiling and formation of networks were observed in the cortical cells. Less competition for space and reliable source of nutrition in the cortex may favor fungal growth. No fungal hyphae were detected in the vascular tissues of seagrasses.
All the endophytic fungi isolated from seagrasses showed antagonistic activity. Aspergillus tamarii, A. ochraceopetaliformis, Penicillium citrinum, Beauveria bassiana, Eutypella sp. and Xylaria sp were the most active antagonists. Antagonistic interaction involved deadlock and replacement. Deadlock was associated with physical blocking of the antagonist’s colony by hyphal aggregation and production of inhibitory metabolites. Demarcation line and colony pigmentation in Xylaria sp. during co-culture assay indicated the production of high quantities of inhibitory molecules. Endophytic fungi in seagrasses also produced volatile organic compounds (VOC) which resulted to deadlock at mycelial distance. Thus, endophyte colonization and distribution in seagrass tissues are influenced by their interaction with the hosts and other endophytes. But interestingly, cyclical intransitivity of multispecies interaction manifested by these fungal species suggested possible co-existence in seagrass tissues.
... Fungi that do not remain endophytic throughout the entire life cycle of the host, and furthermore may not be present during the entire life cycle of the host, are categorized as non-clavicipitaceus endophytes (NC-endophytes) and represent the three functional classes: class 2, defined as containing the fungi colonizing above-and below-ground plant tissues, i.e., the rhizosphere, endorhiza, and aerial tissues [15], and being horizontally and/or vertically transmitted [16]; class 3, defined as containing members of the Dikaryomycota (Ascomycota or Basidiomycota) that are mostly confined to the air tissues of various hosts, especially trees, but also other plant taxa [17,18] and are transmitted horizontally [19]; class 4, which comprise dark, septate endophytes, which, similar to mycorrhizal fungi, are restricted to roots, where they reside inter-and/or intracellularly in the cortical cell layers [20]. Detailed information of fungal endophytes classification has been compiled in the review by Rodriguez et al. [11]. ...
Wheat production is influenced by changing environmental conditions, including climatic conditions, which results in the changing composition of microorganisms interacting with this cereal. The group of these microorganisms includes not only endophytic fungi associated with the wheat endosphere, both pathogenic and symbiotic, but also those with yet unrecognized functions and consequences for wheat. This paper reviews the literature in the context of the general characteristics of endophytic fungi inhabiting the internal tissues of wheat. In addition, the importance of epigenetic regulation in wheat–fungus interactions is recognized and the current state of knowledge is demonstrated. The possibilities of using symbiotic endophytic fungi in modern agronomy and wheat cultivation are also proposed. The fact that the current understanding of fungal endophytes in wheat is based on a rather small set of experimental conditions, including wheat genotypes, plant organs, plant tissues, plant development stage, or environmental conditions, is recognized. In addition, most of the research to date has been based on culture-dependent methods that exclude biotrophic and slow-growing species and favor the detection of fast-growing fungi. Additionally, only a few reports of studies on the entire wheat microbiome using high-throughput sequencing techniques exist. Conducting comprehensive research on the mycobiome of the endosphere of wheat, mainly in the context of the possibility of using this knowledge to improve the methods of wheat management, mainly the productivity and health of this cereal, is needed.
... In parallel transmission situations, proliferation is generally dependent on the reproductive structures of the endophyte, which carry spores that can be blown along with wind or dispersed by rain, as well as by vector-like insects from one plant to another plant in the soil, by air and vector movements. The different class of endophytes, such as 2 and 3, and the colonization of plants occurs through the infected structure, which directly penetrates the hyphae of plant tissue (Ernst et al., 2003;Gao and Mendgen, 2006). The spread of the sexual species of Epichlo¨e (Class 1) horizontally through well-known ascospores (reviewed in Leuchtmann et al., 2014). ...
Endophytes play a vital role in the survival of host plants by aiding defense responses by producing bioactive compounds similar to their host plants. To fulfill the ever-increasing demand for herbal drugs to cure human ailments, researchers are searching for the various sources of bioactive compounds besides medicinal plants. It was reported that in the international market, the demand of 3 kg per year of vinca alkaloids (1.5×106 kg dry leaves are required) to develop powerful plant-derived anticancer drugs. In this regard, this review aims to highlight the endophytes residing in Catharanthus roseus (family: Apocynaceae), capable of synthesizing indole alkaloids, vinblastine, vincristine, vindoline, vinflunine, vincamine, ajmalicine, ajmaline, serpentine, and reserpine used to control cancer, diabetes, malaria, vascular dementia, cardiac diseases, etc. In the search to fulfill the demand, there is urgent need to develop an efficient method of isolation, identification of endophytes, and the down-streaming process for more efficient and sustainable production of vinca alkaloids from endophytic fungus for the cancer treatment products. Microbial fermentation by optimizing media composition, precursors, inducers, and the metabolic bypass inhibitors would be a promising method in the production of vinca alkaloids at industrial scale. Furthermore, different biotechnological strategies such as gene cloning, gene transformation, and mutations can widely be used on endophytic fungi and bacteria in order to increase the productivity of the vinca alkaloids. Thus, advancements in science and technology have increased the extraction yield from vinca alkaloid producing endophytes, thereby improving the overall efficiency of alkaloid production.
Fungal endophytes (FEs) are endosymbionts that live inside the plant and produce compounds that protect the host from predators like grazing animals, pests, and insects. FEs are the repository of novel bioactive compounds, potentially treating various lifestyle and communicable diseases like microbial diseases, viral diseases, parasitic diseases, etc. Bioinformatics plays an essential role in the high-throughput screening of thousands and millions of compounds in a single click at a short time. Several tools and web servers are available to explore compounds, library preparation, protein and ligand preparation, grid generation for specific docking, ADME prediction to predict drug-like properties, docking for high-throughput ligand screening, and finally, molecular dynamics simulation to check the stability of docked protein-ligand complexes. Because of the occurrence of widespread drug resistance as a result of unprescribed and misused antibiotics, there is an urgent need for novel bioactive compounds, and bioinformatics is the first prominent choice for researchers in this strategy. Virtual screening through bioinformatics decreases the number of compounds. Hence, it will be very straightforward for researchers to test a limited number of compounds against specific diseases in in vitro and in vivo studies and reduce prerequisite validation.
Volatile compounds are different mixtures of gaseous, carbonic compounds produced by the fungi and are easily diffused through the atmosphere as well as the soil due to their small size. With a variety of technologies and methodological limitations, scientists have identified 250 fungal volatile compounds characterized by particular odors formed during both primary and secondary metabolism. Various fungal volatile compounds support a provocative diagnosis of a medical condition known as sick building syndrome and are helpful in summing up the successful Trichoderma biocontrol species. Volatile compounds also play an important role in the signaling of fungi in the natural environment. Various ecological interactions are mediated by volatile compounds between fungi, arthropods, bacteria, plants, and other fungi. Fungal volatile compounds have different functions that can be used in the development of biotechnological applications such as biocontrol, biofuel, and mycofumigation. Fungal endophytes have enhanced plant performance and plant protection against both biotic and abiotic stress by undergoing adaptation in the habitat. Fungal endophytes are involved in different secondary metabolites, which also include volatile compounds. In addition to plant protection against pests and pathogens, some fungal endophytes may remove toxicity in animals associated with fungal endophytes in grasses of the temperate region, mainly in corn and rice plants, which are tolerant of biotic and abiotic stress. In bioprospecting, volatility is the new boundary and the assessment of these gaseous compounds has the potential for the discovery of net products that interfere with human exploitation, resulting in the creation of a new hypothesis in fundamental biology.
In recent decades, endophytes have attracted significant attention for their beneficial role in plant health and fitness and have been proposed as effective alternatives to synthetic fertilizers and pesticides. As such, knowledge on nature and mechanisms underpinning plant-endophyte interactions represents an important advancement to enhance our understanding of how plants can benefit from their microbial partners. In this chapter, we review the role of the rhizosphere microbiome in the recruitment of this major subgroup of plant-associated microbes and other factors in the rhizosphere (root exudates, soil properties, and plant genotype) that, together with a range of gene expression and epigenetic mechanisms, directly regulate endophytic colonization. We conclude by highlighting emerging strategies to manipulate these associations to benefit plant health and productivity. The information and facts gathered from current plant microbiome research will greatly improve our ability to harness rhizosphere/endophytic microbiome for viable strategies to improve agricultural production.
The Endophytic Symbiotic Association (ESA) has proven as an important tool in uplifting various areas related to crop productivity, nutritional profile, issues related to sustainability, food quality, and security. These beneficial associations have highlighted the burning scenario that is generally equipped with the conventional and chemical cultivation patterns, but moving toward a safe area which includes the use of EPHs (Enhanced Plant Holobionts) consortiums is a best choice toward a sustainable agriculture. The use of these types of associates with mutualistic associations have benefited the host in terms of increased uptake of nitrogen, efficient utilization of nutrients, increased photosynthetic activity and levels, introducing a systemic resistance toward various plant pathogens, pests, and diseases. Secretion of osmoprotectant, decreasing the availability of ROS (Reactive Oxygen Species) and finally leading to enhanced plant growth, crop productivity, and yields. Further, in this direction many integrated systems (SRI-System of Rice Intensification) have been incorporated with these endophytic symbionts, which have yielded spectacular results in terms of pest resistance and crop yields. Thus, it can be concluded that integrating the endophytic symbiotic associations with the different cropping patterns can easily solve the issues related to crop quality, yields, and sustainability.
Endophytes are ubiquitous in the plant world; no report of a plant species not associated with them is known; all plants in natural ecosystems appear to be symbiotic with fungal endophytes. This highly diverse group of fungi can have profound impacts on plant communities through increasing fitness by conferring abiotic and biotic stress tolerance, increasing biomass and decreasing water consumption, or decreasing fitness by altering resource allocation. Despite more than 100 years of research resulting in thousands of journal articles, the ecological significance of these fungi remains poorly characterized. Historically, two endophytic groups, Clavicipitaceous C and nonclavicipitaceous NC have been discriminated based on phylogeny and life history traits. The NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts. Using this framework, we contrast the life histories, interactions with hosts, and potential roles in plant ecophysiology of C- and NC-endophytes, and highlight several key questions for future work in endophyte biology. Fungal endophytes recovered from plants in terrestrial (agroecosystems and natural) ecosystems ranking from tropical and subtropical, grasslands and savannahs,croplands, hot desert, temperate boreal, tundra, Arctic/Antarctic biomes, alpine, xeric environments, aquatic ecosystems and mangroves.
Lophodermium comprises ascomycetous fungi that are both needle-cast pathogens and asymptomatic endophytes on a diversity of plant hosts. It is distinguished from other genera in the family Rhytismataceae by its filiform ascospores and ascocarps that open by a longitudinal slit. Nucleotide sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA were used to infer phylogenetic relationships within Lophodermium. Twenty-nine sequences from approximately 11 species of Lophodermium were analyzed together with eight sequences from isolates thought to represent six other genera of Rhytismataceae: Elytroderma, Lirula, Meloderma, Terriera, Tryblidiopsis and Colpoma. Two putative Meloderma desmazieresii isolates occurred within the Lophodermium clade but separate from one another, one grouped with L. indianum and the other with L. nitens. An isolate of Elytroderma deformans also occurred within the Lophodermium clade but on a solitary branch. The occurrence of these genera within the Lophodermium clade might be due to problems in generic concepts in Rhytismataceae, such as emphasis on spore morphology to delimit genera, to difficulty of isolating Rhytismataceae needle pathogens from material that also is colonized by Lophodermium or to a combination of both factors. We also evaluated the congruence of host distribution and several morphological characters on the ITS phylogeny. Lophodermium species from pine hosts formed a monophyletic sister group to Lophodermium species from more distant hosts from the southern hemisphere, but not to L. piceae from Picea. The ITS topology indicated that Lophodermium does not show strict cospeciation with pines at deeper branches, although several closely related isolates have closely related hosts. Pathogenic species occupy derived positions in the pine clade, suggesting that pathogenicity has evolved from endophytism. A new combination is proposed, Terriera minor (Tehon) P.R. Johnst.
Fungal plant pathogens penetrate their hosts directly or through wounds, and of those that penetrate directly, a majority use an appressorium to provide a locus of force and enzymatic activity to aid the process. These infection structures usually are developed by the spore germling on the tip of the germ tube; however, some fungi also produce infection cushions at the tip of mycelia, i.e., Saprolegnia spp., where they arise on hyphal apices attracted to the substrata by chemotropism (Willoughby and Hasenjager 1987). The mystery is how fungi decide where to develop infection structures, and how they detect the place for penetration. In fact, selection, often random, may be influenced by the presence of nutrients and a compatible surface. A good review of the process as it was known before 1975 is that by Emmett and Parbery (1975).
Kinetics of the colonization process of beech leaves by Discula umbrinella have been studied. D. umbrinella can either form an appressorium at the end of the germ-tube or penetrate subcuticularly. Penetration through the host cell wall is achieved by a comparatively fine penetration hypha that pierces the cuticular membrane and the epidermal cell wall; the extracellular matrix usually present around both external fungal hyphae and appressoria is absent in subcuticular and subepidermal hyphae. Cuticular and epidermal cell-wall degradation was evident around the penetration hypha. Subcuticularly the fungus was found in the reticulate part of the cuticle, underneath the amorphous layer of the cuticular membrane. The epidermal cell wall underneath the subcuticular hyphae was at least partly digested, and the cytoplasm contained electron-dense compounds that may be of phenolic origin and are probably related to the infection process. At this stage the parenchyma cells were morphologically still intact. At later stages of infection D. umbrinella grew through the epidermal cell wall into the parenchyma and colonized mainly the intercellular spaces of the mesophyll, although intracellular growth was occasionally seen. Transmission electron microscopy studies of appressoria and subcuticular hyphae suggest that enzymic activities could be mainly responsible for fungal penetration. Enzymic digestion of cuticle and epidermis cell walls is also suggested by the presence of electron-transparent material in beech leaf sections, which results probably from the digestion of the cell wall in the vicinity of penetrating hyphae. These results indicate that endophytes penetrate into their host in ways similar to those described for biotrophic and hemibiotrophic pathogenic fungi. Under in vitro conditions, D. umbrinella is able to colonize host tissues, causing conspicuous necroses. The time between infection and onset of the first symptoms varied from 48 h to several days, depending on the infection conditions. During the latent period the fungus is mainly located at the subcuticular or subepidermal level.