A reference transcriptome for walnut anthracnose pathogen, Ophiognomonia leptostyla

Despite the economic losses due to Ophiognomonia leptostyla on walnut trees, no genome or transcriptomereference for the pathogen has yet been available. In the present study, the transcriptome of O. leptostylaisolate SA-SE was assembled using four assemblers i.e., Trinity, Oases, SOAPdenovo-Trans and Bridger.RNA sequencing of fungal mycelia grown on axenic culture and the leaf samples of Persian walnut (cv.Chandler) inoculated with the fungal conidia and sampled at three time points ۴۸h, ۹۶h and ۱۴۴h postinoculation. The completeness and contiguity of assemblies were assessed by tools such as Transrate andBUSCO to identify the superior assembly [۱,۲]. In most of the assessment criteria such as N۵۰, Transratescore, number of ORFs with known description in gene bank, the percentage reads mapped back to thetranscript (RMBT), BUSCO features, SwissProt coverage bin and RESM-EVAL score, the Bridger assemblywas the superior assembler. Next, the expression of transcript was profiled over sampling time point tounderstand how O. leptostyla deploys transcriptome for infection and colonization within host plants. Kmeansclustering of expressed transcripts resulted in transcripts grouped in four different clusters over threesampling time points. Candidate effectors and Cazyme were identified in silico and their co-expressionpattern was examined to identify candidate key genes in infection and host colonization.

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Keywords: Juglans. Regia (cv Chandler) , Ophiognomonia leptostylaRNA-seq , de novo assembly , K-mean analysis , effector