Systematic characterization of the bZIP gene family in Colletotrichum siamense and functional analysis of three family members

Abstract

The basic leucine zipper (bZIP) transcription factors (TFs) play important roles in many physiological processes of plant-pathogenic fungi, especially concerning fungal development, fungicide resistance, and pathogenicity. Colletotrichum siamense is the predominant species causing Colletotrichum leaf disease (CLD) in rubber trees. However, little is known about the bZIP genes in C. siamense. In this study, 25 bZIP genes were systematically identified in the genome of C. siamense, and molecular features were characterized. Evolutionarily, the CsbZIP genes were divided into 11 groups, with the members in the same group sharing similar gene structures and conserved protein motif organizations. Furthermore, protein-protein interaction (PPI) analysis revealed that 15 bZIP proteins had functional partners in common or interacted with other CsbZIP proteins. Additionally, the expression of 23 CsbZIP genes changed in response to the antifungal chemicals melatonin, prochloraz, and thymol, and the genes could be divided into three clusters based on their expression patterns. Finally, gene deletion mutants of CsbZIP01/09/17 were constructed and functional analysis indicated that these genes operated as important regulators of mycelial growth, fungicide resistance, ergosterol biosynthesis, and virulence in C. siamense. This study provided the foundations crucial for further investigation of the functions of CsbZIP TFs in fungicide resistance and virulence.