Identification of Potential Pathogenicity Factors and Host Defense Genes in the Sclerotinia Homoeocarpa – Turfgrass Pathosystem Using Transcriptome Analysis.

Sclerotinia homoeocarpa is the causal agent of agent of dollar spot, the most predominate disease on well-maintained turfgrass. Frequent fungicide applications are costly to turf managers and have resulted in resistance to various fungicides. Currently, there are major gaps in our understanding of the molecular underpinnings of S. homoeocarpa-turfgrass pathosystem.  Advances in next-generation sequencing have enabled researchers to sequence transcriptomes of organisms at a relatively low cost.  In this study, 454 sequencing technology was used in the de novo assembly of both the S. homoeocarpa and creeping bentgrass transcriptomes.  RNA sequence (RNA-seq) libraries were created using S. homoeocarpa and creeping bentgrass culture controls and infected grass harvested at 96 h post inoculation.  RNA-seq libraries were also prepared using 454 sequencing for S. homoeocarpa grown in broth culture for two, four, and six days.  RNA-seq analysis was conducted using Blast2GO and HMMER v3.0 to identify transcripts and conserved protein domains that may be important for S. homoeocarpa pathogenisis and creeping bentgrass defenses.  Fungal transcripts of interest included various polyketide synthases, glycosyl hydrolases, and serine proteases.  Creeping bentgrass transcripts that may be associated with defense include WRKY transcription factors, various jasmonate-induced proteins, callose synthase, GH3, and a large number of transpon sequences.  This analysis provides an extensive overview of the S. homoeocarpa-turfgrass pathosystem at the molecular level and identified key enzymes and pathways that will be further characterized.