Endophytic Diaporthe Diversity, Pezicula Metabolites And Interactions Between Xylaria Striata And Plants

Nowadays endophytic fungi have gained much attention from scientists in related fields for unique niche, high biodiversity and rich natural compound resource they possess. Endophytic fungi in Diaporthe, Pezicula as well as Xylaria are common groups with high biodiversity. This paper demonstrates a systemic research on genetic diversity of Diaporthe endophytes, metabolite isolation and bioactivity analysis from Pezicula sp. as well as interactions between X. striata and plants. All the results obtained are listed as followings.1, Genetic diversity of Diaporthe endophytesAltogether116endophytic Diaporthe isolates were obtained from28plant samples collected in Southeast China. According to alignment result of internal transcribed spacer of ribosomal nucleotide sequences (ITS rDNA),64haplotypes were determined via DnaSP ver.5.1. Twenty-two haplotypes turned out to be phylogenetically distant from known species. Among them,14strains from5discrete terminal clades were chosen for further analysis based on partial sequence of translation elongation factor1-a (tefl-a). Not surprisingly, they got separated from others. Following multi-locus phylogeny analysis based on ITS rDNA, tefl-a, p tubulin and calmodulin grouped8most discrepant strains into3discriminating clusters which resembled3novel species. However only ZJWCF252could form small pycnidia, spindle to stick shaped alpha conidia and rarely gamma conidia.2, Metabolite isolation and bioactivity analysis from Pezicula sp. Another16fungal endophytes were derived from twigs of Forsythia viridissima, Zhejiang Province, China. One of them named ZJWCF069with antifungal activity was selected to go through further analysis. It was identified as Pezicula sp. by combination of morphological and phylogeny analysis. From its fermentation broth, four compounds were obtained through silica gel column chromatography and Sephadex LH-20with the guide of bioassay. Corresponding structures were elucidated via spectroscopic analysis as mellein (1). ramulosin (2). butanedioic acid (3), and4-methoxy-1(3H)-isobenzofuranone (4). Compound4here, as a natural product from microbes, was achieved for the very first time. In vitro antifungal assay demonstrated that compound1displayed a similar antagonism against9phytopathogenic fungi as cyclopaldic acid.3, Interactions between X. striata and plantsAn evolutionary biphasic symbiosis model between mutualistic root symbiont X. striata and rice as well as tobacco was proposed on a case-by-case basis to shed light on fungal phenotypic plasticity and its ecological significance. Biomass elevation of tobacco conferred by X. striata was much more significant than that of rice. Hyphal colonization into rice roots occurred in meristem and elongation areas with an absence of other infection structures. However, this fungus could not infect tobacco roots, and its fermentation broth had no promotion effects on tobacco, suggesting a mechanism of chemical communication during the interaction. Distinct fungal life-cycles and trophic modes during the symbiosis were revealed by global investigation of transcriptional response. X. striata equipped with accelerated enzyme activities could break through the barriers in rice root cells guarded mainly by jasmonates (JAs) pathway, while was blocked by ethylene signaling network at the door of tobacco roots. Greater growth promotion in tobacco could be attributed to additional stimulation of auxin and cytokinin encoding genes apart from gibberellin encoding ones. Moreover, vital importance of redox homeostasis in optimizing growth and development was overrepresented in transcriptomic data, which was further confirmed by ROS accumulation test. Taken together, X. striata possessing both diverse enzymes and root infection toolkit resembles an exquisite linking between free living fungi to plant residing ones in the long run of evolution, which is unprecedented and of great scientific significance.