Transcriptomic Analysis Reveals Candidate Genes Responsive to Sclerotinia scleroterum and Cloning of the Ss -Inducible Chitinase Genes in Morus laevigata

(Ss) is a devastating fungal pathogen that causes Sclerotinia stem rot in rapeseed ( ), and is also detrimental to mulberry and many other crops. A wild mulberry germplasm, , showed high resistance to , but the molecular basis for the resistance is largely unknown. Here, the transcriptome response characteristics of to infection were revealed by RNA-seq. A total of 833 differentially expressed genes (DEGs) were detected after the inoculation in the leaf of . After the GO terms and KEGG pathways enrichment analyses, 42 resistance-related genes were selected as core candidates from the upregulated DEGs. Their expression patterns were detected in the roots, stems, leaves, flowers, and fruits of . Most of them (30/42) were specifically or mainly expressed in flowers, which was consistent with the fact that mainly infects plants through floral organs, and indicated that Ss-resistance genes could be induced by pathogen inoculation on ectopic organs. After the inoculation, these candidate genes were also induced in the two susceptible varieties of mulberry, but the responses of most of them were much slower with lower extents. Based on the expression patterns and functional annotation of the 42 candidate genes, we cloned the full-length gDNA and cDNA sequences of the -inducible chitinase gene set ( family). Phylogenetic tree construction, protein interaction network prediction, and gene expression analysis revealed their special roles in response to infection. In prokaryotic expression, their protein products were all in the form of an inclusion body. Our results will help in the understanding of the molecular basis of -resistance in , and the isolated genes are candidates for the improvement in plant -resistance via biotechnology.