Hettiarachchige Inoka K, Vander Jagt Christy J, Mann Ross C, Sawbridge Timothy I, Spangenberg German C, Guthridge Kathryn M
Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia.
School of Applied Systems Biology, La Trobe University, Bundoora, VIC 3086, Australia.
Microorganisms. 2021 May 4;9(5):991. doi: 10.3390/microorganisms9050991.
Asexual fungi are strictly seed-transmitted endophytic symbionts of cool-season grasses and spend their entire life cycle within the host plant. Endophyte infection can confer protective benefits to its host through the production of bioprotective compounds. Inversely, plants provide nourishment and shelter to the resident endophyte in return. Current understanding of the changes in global gene expression of asexual endophytes during the early stages of host-endophyte symbiotum is limited. A time-course study using a deep RNA-sequencing approach was performed at six stages of germination, using seeds infected with one of three endophyte strains belonging to different representative taxa. Analysis of the most abundantly expressed endophyte genes identified that most were predicted to have a role in stress and defence responses. The number of differentially expressed genes observed at early time points was greater than those detected at later time points, suggesting an active transcriptional reprogramming of endophytes at the onset of seed germination. Gene ontology enrichment analysis revealed dynamic changes in global gene expression consistent with the developmental processes of symbiotic relationships. Expression of pathway genes for biosynthesis of key secondary metabolites was studied comprehensively and fuzzy clustering identified some unique expression patterns. Furthermore, comparisons of the transcriptomes from three endophyte strains in planta identified genes unique to each strain, including genes predicted to be associated with secondary metabolism. Findings from this study highlight the importance of better understanding the unique properties of individual endophyte strains and will serve as an excellent resource for future studies of host-endophyte interactions.
无性真菌是冷季型禾本科植物严格通过种子传播的内生共生体，其整个生命周期都在宿主植物体内度过。内生菌感染可通过产生生物保护化合物为宿主带来保护益处。反过来，植物则为内生菌提供营养和庇护作为回报。目前对于无性内生菌在宿主 - 内生菌共生体早期阶段全球基因表达变化的了解有限。我们采用深度RNA测序方法，在种子萌发的六个阶段，对感染了三种不同代表性分类群的内生菌菌株之一的种子进行了时间进程研究。对表达最丰富的内生菌基因的分析表明，大多数基因预计在应激和防御反应中发挥作用。在早期时间点观察到的差异表达基因数量多于后期时间点检测到的数量，这表明在种子萌发开始时内生菌发生了活跃的转录重编程。基因本体富集分析揭示了与共生关系发育过程一致的全球基因表达动态变化。我们全面研究了关键次生代谢物生物合成途径基因的表达，并通过模糊聚类确定了一些独特的表达模式。此外，对植物中三种内生菌菌株转录组的比较确定了每个菌株特有的基因，包括预计与次生代谢相关的基因。这项研究的结果凸显了更好地了解单个内生菌菌株独特特性的重要性，并将为未来宿主 - 内生菌相互作用的研究提供极好的资源。
