A fungal plant pathogen Sclerotinia homoeocarpa and its host Agrostis stolonifera Transcriptome or Gene expression

Sclerotinia homoeocarpa causes dollar spot disease, the predominant disease on highly-maintained turfgrass. Currently, there are major gaps in our understanding of the molecular interactions between S. homoeocarpa and creeping bentgrass. In this study, 454 sequencing technology was used in the de novo assembly of S. homoeocarpa and creeping bentgrass transcriptomes. Additional transcript sequence data was obtained using Illumina’s first generation sequencing-by-synthesis (SBS) for S. homoeocarpa culture controls, creeping bentgrass uninoculated controls, and for creeping bentgrass inoculated with S. homoeocarpa and incubated for 96 h. SBS reads were mapped to the transcript assemblies and a Fisher’s exact test was performed to determine transcripts that were significantly different during creeping bentgrass infection with S. homoeocarpa. Fungal transcripts of interest included glycosyl hydrolases, proteases, and ABC transporters. Of particular interest were the large number of glycosyl hydrolase transcripts that target a wide range of plant cell wall compounds, corroborating the suggested wide host range and saprophytic abilities of S. homoeocarpa. Several of the multidrug resistance ABC transporters may be important for resistance to both fungicides and plant defense compounds. Creeping bentgrass transcripts of interest included germins, ubiquitin transcripts involved in proteasome degradation, and cinnamoyl reductase, which is involved in lignin production. This analysis provides an extensive overview of the S. homoeocarpa-turfgrass pathosystem and provides a starting point for the characterization of potential virulence factors and host defense responses. In particular, determination of important host defense responses may assist in the development of highly resistant creeping bentgrass varieties.

双核丝核菌（Sclerotinia homoeocarpa）可引发钱斑病，该病害是高养护草坪草上的主要病害。目前，学界对该病原菌与匍匐翦股颖（creeping bentgrass）之间的分子互作机制仍存在较大认知空白。本研究采用454测序技术，完成了双核丝核菌与匍匐翦股颖的转录组从头组装（de novo assembly）。此外，本研究还利用Illumina第一代合成测序（sequencing-by-synthesis, SBS）技术，获取了三类样本的转录序列数据：双核丝核菌培养对照组、未接种的匍匐翦股颖对照组，以及接种双核丝核菌并培养96小时的匍匐翦股颖样本。研究中将SBS测序读段（reads）比对至转录组装结果，并通过费希尔精确检验（Fisher’s exact test）筛选出匍匐翦股颖被双核丝核菌侵染过程中差异显著的转录本。靶标真菌转录本包括糖基水解酶（glycosyl hydrolases）、蛋白酶以及ABC转运蛋白（ABC transporters）。尤为值得关注的是，大量靶向多种植物细胞壁组分的糖基水解酶转录本被检出，这佐证了双核丝核菌具有广泛寄主范围与腐生能力的已有推测。部分多药耐药性ABC转运蛋白可能在病原菌抵御杀菌剂与植物防御物质过程中发挥重要作用。匍匐翦股颖的靶标转录本包括萌发素（germins）、参与蛋白酶体降解的泛素转录本，以及参与木质素合成的肉桂酰还原酶（cinnamoyl reductase）。本分析全面解析了双核丝核菌-草坪草病害互作系统（pathosystem），为潜在致病因子（virulence factors）的功能鉴定与寄主防御反应研究提供了基础起点。具体而言，对关键寄主防御反应的解析，将有助于培育高抗匍匐翦股颖品种。