Functional analysis of SCD1 gene involved in pathogenicity of spot blotch disease of wheat causing fungus Bipolaris sorokiniana

Abstract

Spot blotch of wheat is an important disease of wheat mainly of warm and humid areas. Melanin produced by various fungi has an important role to play in survival and longevity of fungal propagules against various environmental stresses through providing structural strength. Melanin production is positively correlated with virulence and conidiogenesis that varies in different isolates of plant pathogenic fungus Bipolaris sorokiniana. Scytalone dehydratase gene (SCD1) plays an important role in synthesis of fungal dihydroxynaphthalene melanin. In this study, the SCD1 gene was isolated, characterized and its DNA sequence along with flanking regions was determined. Structural analysis of gene revealed that 516 bp un-interpreted open reading frame. Sequence analysis showed that SCD1 gene encodes a 180 amino acids putative protein. A comparison of the predicted amino acid sequence and actual nucleotide sequence of the SCD1 gene was made with other fungal reductase genes involved in melanin biosynthesis which indicates 56–98% sequence identity. Targeted disruption of SCD1gene revealed that this gene is necessary for melanin biosynthesis in B. sorokiniana. SCD1 gene mutant isolate lack melanin synthesis and showed significant reduction in pathogenicity on wheat plants. This study expands our knowledge and provides comprehensive understanding of the pathogenesis of B. sorokiniana and insight of fungal phytopathogens.