In Silico Characterization of bZIP Transcription Factor Gene Family and its Expression Under Abiotic Stress in Spinacia oleracea

Abstract

Spinach (Spinacia oleracea) is one of the most nutritionally valuable leafy vegetables cultivated and consumed worldwide. The basic leucine zipper (bZIP) transcription factors are key regulators in abiotic stress responses; however, a comprehensive genome-wide analysis of the bZIP gene family in S. oleracea has not yet been conducted. In this study, we identified 45 non-redundant SobZIP genes distributed unevenly across six chromosomes and further analyzed their evolutionary classification, physicochemical properties, conserved domain analysis, functional differentiation and expression patterns. As the first genome-wide survey of the bZIP family in spinach, this work extends comparative knowledge of the family in the Amaranthaceae, shows that spinach retains 12 of the 13 Arabidopsis bZIP subfamilies, and identifies candidate genes responsive to heat stress and salicylic acid treatment for future functional studies. Phylogenetic comparison with Arabidopsis thaliana bZIPs classified the SobZIPs into 12 distinct subfamilies, highlighting their evolutionary conservation and potential functional divergence. Cis-regulatory element analysis of promoter regions revealed numerous predicted stress- and hormone-responsive elements, suggesting possible regulatory roles in development and stress adaptation. Moreover, RNA-seq-based expression analysis under heat stress and salicylic acid (SA) treatment revealed several candidate stress-responsive genes, notably SobZIP02, SobZIP14, SobZIP20 and SobZIP43. Our research provides a basis for future functional studies and, after experimental validation, may support the development of S. oleracea cultivars with enhanced heat tolerance and improved salicylic acid-associated defense responses.