Genome-wide characterization and expression analysis of the SULTR gene family in Cicer arietinum: regulates the sulfate transport/assimilation under sulfur starvation

Chickpea ( Cicer arietinum L. ) is a major pulse crop; however, its protein quality is limited due to low levels of sulfur-containing amino acids. Sulfur deficiency in agricultural soils necessitates improved sulfate uptake and assimilation efficiency. Despite advances in understanding plant sulfate transporters (SULTRs), their molecular complexity and functional roles in legumes remain poorly understood. A total of 15 CaSULTR genes were identified, encoding proteins with conserved Sulfate_transp (PF00916) and STAS (PF01740) domains. These genes were classified into four groups based on phylogenetic, duplication, and synteny analyses. Their expansion was primarily driven by dispersed and whole-genome duplication under purifying selection. Promoter analysis revealed the presence of stress-, hormone-, growth-and-development-, and light-responsive cis-elements, suggesting complex regulation. In silico analysis revealed tissue-specific patterns with CaSULTR2 highly induced in roots and CaSULTR8 showing shoot-specific expression. Comparative physiological analysis of seedlings grown under sulfur-sufficient (2 mM SO42−) and sulfur-starvation (0 mM SO42−) conditions was performed. Higher sulfur-efficient cultivars (PUSA256 and PUSA1003) exhibited improved biomass, root architecture, and enhanced enzyme activities (SERAT and OASTL), along with increased SULTR gene expression (Figs. 7, 8, and 9). Conversely, PUSA3022 showed poor growth and a weak transcriptional response. This study provides comprehensive insights into the evolution, regulation, and functional role of CaSULTR genes in sulfate transport and assimilation. Physiological and expression analyses indicate that enhanced SULTR activity and sulfur assimilation improve sulfur-use efficiency in tolerant chickpea cultivars, highlighting these candidate genes and associated physiological traits as potential targets for improving sulfate-use efficiency in chickpea breeding programs.