Ecology Of Endophytes Research Articles

Methodological Approaches Frame Insights into Endophyte Richness and Community Composition.

Isolating microbes is vital to study microbiomes, but insights into microbial diversity and ecology can be constrained by recalcitrant or unculturable strains. Culture-free methods (e.g., next-generation sequencing, NGS) have become popular in part because they detect greater richness than culturing alone. Both approaches are used widely to characterize microfungi within healthy leaves (foliar endophytes), but methodological differences among studies can constrain large-scale insights into endophyte ecology. We examined endophytes in a temperate plant community to quantify how certain methodological factors, such as the choice of cultivation media for culturing and storage period after leaf collection, affect inferences regarding endophyte communities; how such effects vary among plant taxa; and how complementary culturing and NGS can be when subsets of the same plant tissue are used for each. We found that endophyte richness and composition from culturing were consistent across five media types. Insights from culturing and NGS were largely robust to differences in storage period (1, 5, and 10days). Although endophyte richness, composition, and taxonomic diversity identified via culturing vs. NGS differed markedly, both methods revealed host-structured communities. Studies differing only in cultivation media or storage period thus can be compared to estimate endophyte richness, composition, and turnover at scales larger than those of individual studies alone. Our data show that it is likely more important to sample more host species, rather than sampling fewer species more intensively, to quantify endophyte diversity in given locations, with the richest insights into endophyte ecology emerging when culturing and NGS are paired.

Endophytic microorganisms in fundamental research and agriculture

The ubiquity of endophytic microorganisms is an accepted fact nowadays and the possibility of using it in agriculture keeps attracting attention of scientific community. In contrast to rhizospheric (living on root surface) and phyllospheric (colonizing aerial parts of plants) members of plant-microbial interactions endophytes are able to establish closer relationships with host-plant, in some cases strongly influencing its phenotype, bringing benefits. However, these microorganisms do not form any specific structures like nodules in case of symbiosis between legumes and rhizobium bacteria. Having a great amount of functions including phytohormone level modulation, vitamins production and nutrient supply improving, endophytes could serve as a basis for biofertilizer, which could potentially minimize the necessity of mineral fertilizers, thus reducing the negative impact of the latter on soil fertility, biodiversity and human health. Our main aim here is to highlight the question of functional significance of endophytes and endophytic bacteria in particular, as well as the way of its application in agriculture and to identify key points in understanding biology of these organisms. In this review we will consider such aspects of plant-endophytic symbiosis as biodiversity of legume and non-legume endophytes, ecology of endophytes and some ways which are commonly in use by studying these microorganisms.

Fungal endophytes: modifiers of plant disease.

Many recent studies have demonstrated that non-pathogenic fungi within plant microbiomes, i.e., endophytes ("endo"=within, "phyte"=plant), can significantly modify the expression of host plant disease. The rapid pace of advancement in endophyte ecology warrants a pause to synthesize our understanding of endophyte disease modification and to discuss future research directions. We reviewed recent literature on fungal endophyte disease modification, and here report on several emergent themes: (1) Fungal endophyte effects on plant disease span the full spectrum from pathogen antagonism to pathogen facilitation, with pathogen antagonism most commonly reported. (2) Agricultural plant pathosystems are the focus of research on endophyte disease modification. (3) A taxonomically diverse group of fungal endophytes can influence plant disease severity. And (4) Fungal endophyte effects on plant disease severity are context-dependent. Our review highlights the importance of fungal endophytes for plant disease across a broad range of plant pathosystems, yet simultaneously reveals that complexity within plant microbiomes presents a significant challenge to disentangling the biotic environmental factors affecting plant disease severity. Manipulative studies integrating eco-evolutionary approaches with emerging molecular tools will be poised to elucidate the functional importance of endophytes in natural plant pathosystems that are fundamental to biodiversity and conservation.

Currencies of mutualisms: sources of alkaloid genes in vertically transmitted epichloae.

The epichloae (Epichloë and Neotyphodium species), a monophyletic group of fungi in the family Clavicipitaceae, are systemic symbionts of cool-season grasses (Poaceae subfamily Poöideae). Most epichloae are vertically transmitted in seeds (endophytes), and most produce alkaloids that attack nervous systems of potential herbivores. These protective metabolites include ergot alkaloids and indole-diterpenes (tremorgens), which are active in vertebrate systems, and lolines and peramine, which are more specific against invertebrates. Several Epichloë species have been described which are sexual and capable of horizontal transmission, and most are vertically transmissible also. Asexual epichloae are mainly or exclusively vertically transmitted, and many are interspecific hybrids with genomic contributions from two or three ancestral Epichloë species. Here we employ genome-scale analyses to investigate the origins of biosynthesis gene clusters for ergot alkaloids (EAS), indole-diterpenes (IDT), and lolines (LOL) in 12 hybrid species. In each hybrid, the alkaloid-gene and housekeeping-gene relationships were congruent. Interestingly, hybrids frequently had alkaloid clusters that were rare in their sexual ancestors. Also, in those hybrids that had multiple EAS, IDT or LOL clusters, one cluster lacked some genes, usually for late pathway steps. Possible implications of these findings for the alkaloid profiles and endophyte ecology are discussed.

Bioactive secondary metabolites produced by microorganisms associated with plants

AbstractIn the past few decades groups of scientists have focused their study on relatively new microorganisms called endophytes. By definition these microorganisms, mostly fungi and bacteria, colonise the intercellular spaces of the plant tissues. The mutual relationship between endophytic microorganisms and their host plants, taxanomy and ecology of endophytes are being studied. Some of these microorganisms produce bioactive secondary metabolites that may be involved in a host-endophyte relationship. Recently, many endophytic bioactive metabolites, known as well as new substances, possesing a wide variety of biological activities as antibiotic, antitumor, antiinflammatory, antioxidant, etc. have been identified. The microorganisms such as endophytes may be very interesting for biotechnological production of bioactive substances as medicinally important agents. Therefore the aim of this review is to briefly characterize endophytes and summarize the structuraly different bioactive secondary metabolites produced by endophytic microorganisms as well as microbial sources of these metabolites and their host plants.

Evaluation of the Nitrogen-fixing Ability of Endophytic Clostridia based on Acetylene Reduction and Reverse Transcription-PCR Targeting the nifH Transcript and Ribosomal RNA

To examine whether plant-derived clostridia and their consortium fix nitrogen in plants, an inoculation system was developed using the grass Miscanthus sinensis under aseptic conditions. Among 13 clostridial strains previously isolated from M. sinensis, Clostridium sp. strain Kas107-1 was selected as the best colonizer in the plant with the non-diazotrophic bacterium Entrobacter sp. strain B901-2. Nitrogen-fixing (acetylene-reducing) activity was not observed in the plants inoculated with Kas107-1 without a carbon source. On the other hand, nitrogenfixing activity was detected when carbon sources were supplied to the roots. To confirm the endophytic nitrogenfixing activity, we cloned nifH genes and monitored their expression in strain Kas107-1. Although this bacterium possessed at least two copies of nifH (nifH1 and nifH2), the nifH1 transcript was exclusively detected in free-living cells and endophytic cells in the plants by reverse transcription (RT)-PCR analysis. RT-PCR analysis of ribosomal RNA suggested the endophytic colonization of the plants by Kas107-1. These results indicate that Clostridium sp. strain Kas107-1 can potentially fix nitrogen in plants. A RT-PCR analysis targeting both functional gene transcripts and the ribosomal RNA molecule is useful for researching endophyte ecology, because their function and colonization in plants can be examined simultaneously with a single preparation of RNA.