Genome Sequencing Analysis of Scleromitrula shiraiana, a Causal Agent of Mulberry Sclerotial Disease With Narrow Host Range

Abstract

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 11,327 protein-coding genes. The number of genes and genome size of S. shiraiana are similar to most other Ascomycetes. The cross-similarities and differences of S. shiraiana with the closely related Sclerotinia sclerotiorum and Botrytis cinerea indicated that S. shiraiana differentiated earlier from their common ancestor. A comparative genomic analysis showed that S. shiraiana has fewer genes encoding cell wall-degrading enzymes (CWDEs) and effector proteins than that of S. sclerotiorum and B. cinerea, as well as many other Ascomycetes. This is probably a key factor in the weaker aggressiveness of S. shiraiana to other plants. S. shiraiana has many species-specific genes encoding secondary metabolism core enzymes. 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 many Sclerotiniaceae fungi, and may be essential for survival and infection. Our results provide insights into the narrow host range of S. shiraiana and its adaptation to mulberries.

Infection Process and Genome Assembly Provide Insights into the Pathogenic Mechanism of Destructive Mycoparasite Calcarisporium cordycipiticola with Host Specificity

“…In the genome of E. weberi, a specific parasite of ant cultivated Leucoagaricus spp., the depletion of CAZymes was also found [100]. There were fewer genes encoding cell wall-degrading enzymes and effector proteins in the genome of Sclerotinia shiraiana than those of Sclerotinia sclerotiorum and B. cinerea, which was probably a key factor of the narrow host range of S. shiraiana [88].…”

“…For the congeneric fungi, Calcarisporium parasiticum has been observed to parasitize several species of Physalospora and closely related fungi [87]. Scleromitrula shiraiana is a causal agent of mulberry sclerotial disease with a narrow host range but includes some species of genus Morus [88].…”

Investigation and rapid detection of fungal pathogens causing mulberry sclerotial disease in south‐west China

“…shiraiana had fewer cell wall‐degrading enzymes and effector proteins, and C . shiraiana had fewer effector proteins, which may be related to their narrow host range (Lv, He, et al, 2021; Zhu et al, 2021). The differences in the genome composition of the pathogens of mulberry sclerotial disease indicate that they have different infection mechanisms.…”

“…Transcriptome sequencing of mulberry fruits infected with C. shiraiana and C. carunculoides showed that pathogen infection stimulated the host's secondary metabolic pathways and defence-related hormone pathways (Bao et al, 2020;Lv, Hao, et al, 2021). The activation of salicylic acid signalling regulated by pathogens may be beneficial to infection by the pathogens (Lv, Hao, et al, 2021). However, it is not clear what effect the replacement of the dominant pathogen or the change of composition ratio of pathogens can have on disease occurrence.…”

“…At present, the pathogenesis of the three pathogens is still poorly understood. Recent genome sequencing data showed that, compared with other necrotrophic fungi, S. shiraiana had fewer cell wall-degrading enzymes and effector proteins, and C. shiraiana had fewer effector proteins, which may be related to their narrow host range (Lv, He, et al, 2021;Zhu et al, 2021). The differences in the genome composition of the pathogens of mulberry sclerotial disease indicate that they have different infection mechanisms.…”