The bZIP gene family in Setosphaeria turcica: identification and expression analysis during HT-toxin induction process

Abstract:

[Objective] The basic leucine zipper (bZIP) factors are a group of large and conserved transcription factors in eukaryotes, and they are involved in the growth, development, and infection of pathogenic fungi in plants. This study aims to identify the bZIP transcription factors in the whole genome of Setosphaeria turcica and explore their functions during HT-toxin induction. [Methods] The members of the bZIP family were screened and identified from the genome database of Setosphaeria turcica, and their physicochemical properties, conserved domains, subcellular localization, cis-acting elements, phylogenetic relationship, and protein-protein interaction network were analyzed. The RNA-seq database was used to analyze the expression of bZIP family members during pathogen infection and HT-toxin induction. [Results]Fourteen bZIP family members (StbZIP1–14) were screened from the genome of Setosphaeria turcica, with significant differences in physical and chemical properties. These factors had the lengths of 226–613 aa, relative molecular weights of 25.24–66.30 kDa, isoelectric points of 4.66–10.36, and the subcellular localization in the nucleus. These factors carried 660 cis-acting elements involved in abiotic stress, hormone induction, cell cycle regulation, enhancers, and core promoters. The phylogenetic analysis with 11 other major pathogenic fungi in plants indicated that StbZIPs were clustered into 10 groups and had a clear co-linear relationship with AabZIPs of Alternaria alternata. The expression levels of StbZIP1, StbZIP5, StbZIP7, StbZIP10, and StbZIP11were significantly correlated with HT-toxin induction, among which StbZIP5 had the highest expression level and demonstrated upregulated expression after 21 days and 28 days of HT-toxin induction. The protein-protein interaction network of StbZIPs predicted three StbZIPs interaction pathways centered on StbZIP5. [Conclusion] The members of the bZIP family of Setosphaeria turcica have significant physicochemical and structural differences, extensive genetic diversity, and significant functional differentiation, playing an important role in transcriptional regulation during HT-toxin induction.