Identification and Expression Analysis of Siderophore Synthetic Gene Cluster of Setosphaeria turcica
Iron is an essential element for microbial growth and plays a crucial role in processes such as oxygen metabolism,electron transfer,DNA and RNA synthesis.Microbes primarily rely on siderophores to absorb iron ions from their environment.Siderophores,as low molecular weight iron chelators secreted by microbes,assist in transporting iron ions within the organism.Fungi primarily use non-ribosomal peptide synthetase-encoded genes as the core of secondary metabolic biosynthetic gene clusters to synthesize siderophores.This study aimed to clarify the siderophore function and biosynthetic process of Setosphaeria turcica.The type of siderophores synthesized by S.turcica was identified using CAS(chrome azurol sulphonate),and its biosynthetic gene cluster was predicted using the AntiSMASH website.Transcriptional data from different developmental stages of S.turcica spores and qRT-PCR analysis of the expression levels of key genes in the siderophore biosynthetic gene cluster during pathogen infection were utilized.The results showed that S.turcica produces hydroxamate-type siderophores.One biosynthetic gene cluster responsible for hydroxamate-type siderophore production was identified in the genome.This cluster consisted of 12 genes with the core gene StNPS6 encoding non-ribosomal peptide synthetase.During spore germination and infection process of S.turcica,several genes in the cluster exhibited significant upregulation.The core gene StNPS6 had an expression level 5.52 times higher at 6 d post-infection compared to the early infection stage,and the auxiliary biosynthesis gene StrhbE showed a 24.12-fold increase in expression at 9 d post-infection.Additionally,the transport-related gene Stpmd1 increased significantly by 19.95-fold at 9 d post-infection.At the same time,it was observed that both iron-rich and iron-deficient conditions had a certain inhibitory effect on the growth of the pathogen.Moreover,under iron-rich conditions,melanin synthesis in the pathogen was hindered.The differences in iron content in the medium led to significant changes in the expression levels of multiple genes within the gene cluster,especially the transport-related protein gene Stpmd1,which showed a 73.28-fold increase in expression under iron-rich conditions.This study provides a foundation for understanding the potential role of siderophores in S.turcica.
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