Scleromitrula shiraiana strain:SX-001 Genome sequencing and assembly. Scleromitrula shiraiana strain:SX-001

Scleromitrula shiraiana is a necrotrophic fungus with a narrow host range, and is one of the main causal pathogens of mulberry sclerotial disease. However, its molecular mechanisms and pathogenesis are unclear. Here, we report a 39.0 Mb high-quality genome sequence for S. shiraiana strain SX-001. The S. shiraiana genome contains 8308 protein-coding genes. The counts of genes per mega genome sequence (CGMG) of S. shiraiana is very low among Ascomycetes. A comparative genomic analysis showed that S. shiraiana has significantly fewer genes encoding cell wall-degrading enzymes (CWDEs) and effector proteins than do the closely related necrotrophs Sclerotinia sclerotiorum and Botrytis cinerea, as well as many other Ascomycetes. This is a key factor in the weaker infection ability of S. shiraiana, compared with that of other necrotrophs. Of the 25 putative effector proteins encoded in the S. shiraiana genome, two were found to induce cell death in tobacco. S. shiraiana has similar numbers of secondary metabolism core genes as S. sclerotiorum and B. cinerea, but the types of genes are strikingly different. The diversity of secondary metabolites may be related to the adaptation of these pathogens to specific ecological niches. However, melanin and oxalic acid are conserved metabolites among all Sclerotiniaceae fungi, and may be essential for survival and infection. Our results provide insights into the narrow host range of S. shiraiana.