Genome-wide and transcriptomic characterization of the GRAS transcription factor family in cowpea (Vigna unguiculata)

The GRAS transcription factor (TF) family is known for its role in plant development and stress signaling, yet has not been characterized in cowpea (Vigna unguiculata). This study fills that gap by identifying and analyzing the GRAS gene family in the cowpea (VuGRAS) reference genome and exploring their expression under abiotic (root-zone desiccation) and biotic (wounding-assisted CABMV or CPSMV inoculation) stress conditions. A total of 57 VuGRAS genes were identified. Gene structure analysis showed that most lack introns. Protein predictions revealed characteristics such as nuclear localization, high acidity, and negative GRAVY values (suggesting hydrophilic character). These genes are unevenly distributed across the 11 chromosomes, with dispersed tandem, and proximal duplications driving gene family expansion. Phylogenetic analysis grouped the VuGRAS proteins into 16 subfamilies, each with conserved motif patterns. Promoter regions displayed cis-regulatory elements linked to stress-responsive TFs, particularly DOF factors. Functional annotation via GO and KEGG associated VuGRAS genes with diverse biological processes, including hormone signaling. Under root-zone desiccation (RZD) stress, VuGRAS genes were predominantly induced at RZD25’ and predominantly repressed at RZD150’, indicating a dynamic, time-dependent role in stress adaptation. VuGRAS6.1 and VuGRAS8.1 were consistently induced across these stress stages, positioning them as priority candidates for functional validation in cowpea dehydration responses. Initial times (up to 16 h) of wounding-assisted viral inoculations had limited effects on VuGRAS expression, suggesting restricted early involvement and/or later-stage regulatory roles. These findings enhance our understanding of VuGRAS in plant stress adaptation and support future functional studies for cowpea genetic improvement. First genome-wide characterization of cowpea GRAS transcription factors, revealing time-dependent transcriptional responses to root-zone desiccation; VuGRAS6.1 and VuGRAS8.1 emerge as consistently induced candidates, positioning them as priority targets for functional validation in cowpea dehydration responses.