1 Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, U.S.A.; and.
2 USDA-ARS, Forage-Animal Production Research Unit, Lexington, KY 40546, U.S.A.
Mol Plant Microbe Interact. 2019 Feb;32(2):194-207. doi: 10.1094/MPMI-10-17-0251-R. Epub 2018 Nov 30.
Epichloë species are fungal symbionts (endophytes) of cool-season grasses that transmit vertically via inflorescence primordia (IP), ovaries (OV), and ultimately, embryos. Epichloë coenophiala, an endophyte of tall fescue (Schedonorus arundinaceus), provides multiple protective benefits to the grass. We conducted transcriptome analysis of the tall fescue-E. coenophiala symbiosis, comparing IP, OV, vegetative pseudostems (PS), and the lemma and palea (LP) (bracts) of the young floret. Transcriptomes of host OV and PS exhibited almost no significant differences attributable to endophyte presence or absence. Comparison of endophyte gene expression in different plant parts revealed numerous differentially expressed genes (DEGs). The 150 endophyte DEGs significantly higher in PS over OV included genes for alkaloid biosynthesis and sugar or amino acid transport. The 277 endophyte DEGs significantly higher in OV over PS included genes for protein chaperones (including most heat-shock proteins), trehalose synthesis complex, a bax inhibitor-1 protein homolog, the CLC chloride ion channel, catalase, and superoxide dismutase. Similar trends were apparent in the Brachypodium sylvaticum-Epichloë sylvatica symbiosis. Gene expression profiles in tall fescue IP and LP indicated that the endophyte transcriptome shift began early in host floral development. We discuss possible roles of the endophyte DEGs in colonization of reproductive grass tissues.
类黑粉菌属真菌是冷季型禾草的共生体（内生菌），通过花序原基（IP）、子房（OV）垂直传播，并最终传播到胚胎。类黑粉菌 coenophiala 是高羊茅（Schedonorus arundinaceus）的内生菌，为草提供多种保护益处。我们对高羊茅-E. coenophiala 共生体进行了转录组分析，比较了花序原基、子房、营养假茎（PS）和幼小花序的外稃和内稃（苞片）。宿主子房和 PS 的转录组几乎没有因内生菌的存在与否而产生显著差异。比较不同植物部位内生菌基因表达情况发现了大量差异表达基因（DEGs）。PS 中比 OV 显著更高的 150 个内生菌 DEGs 包括生物碱生物合成和糖或氨基酸转运的基因。OV 中比 PS 显著更高的 277 个内生菌 DEGs 包括蛋白质伴侣（包括大多数热休克蛋白）、海藻糖合成复合物、bax 抑制剂-1 蛋白同源物、CLC 氯离子通道、过氧化氢酶和超氧化物歧化酶的基因。在野牛草-Epichloë sylvatica 共生体中也出现了类似的趋势。高羊茅花序原基和外稃的基因表达谱表明，内生菌转录组的变化早在宿主花发育早期就开始了。我们讨论了内生菌 DEGs 在生殖草组织定殖中的可能作用。
