Ovarian Tumor Domain-Containing Proteases-Deubiquitylation Enzyme Gene SsCI33130 Involved in the Regulation of Mating/Filamentation and Pathogenicity in Sporisorium scitamineum

Abstract

Sugarcane is an important sugar crop. Sugarcane smut, caused by Sporisorium scitamineum, is a worldwide sugarcane disease with serious economic losses and lack of effective control measures. Revealing the molecular pathogenesis of S. scitamineum is very helpful to the development of effective prevention and control technology. Deubiquitinase removes ubiquitin molecules from their binding substrates and participates in a variety of physiological activities in eukaryotes. Based on the transcriptome sequencing data of two isolates (Ss16 and Ss47) of S. scitamineum with different pathogenicities, SsCI33130, a gene encoding an OTU1-deubiquitin enzyme, was identified. The positive knockout mutants and complementary mutants of the SsCI33130 gene were successfully obtained through polyethylene glycol-mediated protoplast transformation technology. In order to study the possible function of this gene in pathogenicity, phenotypic comparison of the growth, morphology, abiotic stress, sexual mating, pathogenicity, and gene expression levels of the knockout mutants, complementary mutants, and their wild type strains were conducted. The results demonstrated that the gene had almost no effect on abiotic stress, cell wall integrity, growth, and morphology, but was related to the sexual mating and pathogenicity of S. scitamineum. The sexual mating ability and pathogenicity between the knockout mutants or between the knockout mutant and wild type were more significantly reduced than between the wild types, the complementary mutants, or the wild types and complementary mutants. The sexual mating between the knockout mutants or between the knockout mutant and wild type could be restored by the exogenous addition of small-molecule signaling substances such as 5 mM cyclic adenosine monophosphate (cAMP) or 0.02 mM tryptophol. In addition, during sexual mating, the expression levels of tryptophol and cAMP synthesis-related genes in the knockout mutant combinations were significantly lower than those in the wild type combinations, while the expression levels in the complementary mutant combinations were restored to the level of the wild type. It is speculated that the SsCI33130 gene may be involved in the development of sexual mating and pathogenicity in S. scitamineum by regulating the synthesis of the small-molecule signaling substances (cAMP or tryptophol) required during the sexual mating of S. scitamineum, thereby providing a molecular basis for the study of the pathogenic mechanisms of S. scitamineum.

Squalene Monooxygenase Gene SsCI80130 Regulates Sporisorium scitamineum Mating/Filamentation and Pathogenicity

“…In this study, the expression of the SsCI80130 gene in the knockout mutants was not detected during the haploid sporidia culture, sexual mating culture, or sugarcane bud infection, while the expression level of the gene in the complementary mutants returned to that of the wild type. These results showed that the quality of knockout mutants and complementary mutants constructed in this study was reliable (the SsCI80130 gene was completely deleted in the knockout mutants and almost completely restored in the complementary mutants), which was similar to a previous study on S. scitamineum by Li et al [ 16 , 37 ]. The obtained high-quality knockout mutants and complementary mutants laid the foundation for further gene function research.…”

“…Furthermore, there was no obvious difference in the morphology of the recovered hyphae and the hyphae produced under the normal condition. The results showed that the SsCI80130 gene may regulate the sexual mating and pathogenicity of S. scitamineum by regulating the cAMP signaling pathway and synthesis of the tryptophol, which is similar to the findings of Li et al [ 37 ]. Moreover, in the abiotic-stress experiment with the addition of CR, SDS, or H 2 O 2 , the growth rate of the knockout mutants was significantly inhibited compared to the wild type and complementary mutants, indicating that the SsCI80130 gene also plays an important role in maintaining the cell-wall integrity and oxidative-stress tolerance of S. scitamineum .…”

“…The cAMP signaling pathway is highly correlated with morphological transition and pathogenicity in dimorphic fungi [ 46 , 47 ]. The obstruction of cAMP synthesis affects the sexual mating of S. scitamineum , resulting in its inability to produce dikaryotic hyphae, but the sexual mating ability could be restored by the addition of exogenous small-molecular substance cAMP [ 13 , 33 , 37 ]. The cAMP signaling pathway also affects the morphological transition of Ustilago maydis .…”

Recent Progress of Deubiquitinating Enzymes in Human and Plant Pathogenic Fungi

“…The Δ MoUBP8 mutant is slightly reduced in both mycelial growth and melanin synthesis [ 52 ]. In S. scitamineum , the DUB gene SsCI33130 is not relevant to growth [ 57 ].…”

“…For the plant pathogenic fungus S. scitamineum , sexual mating is closely related to its pathogenicity. The OTU1 deubiquitinase gene SsCI33130 regulates the expression of genes involved in the synthesis of cAMP and tryptophol [ 57 ]. The cAMP and tryptophol are small molecule signaling substances required for the sexual mating of S. scitamineum .…”