Comprehensive Genomic Analysis of GRAS Transcription Factors Reveals Salt-Responsive Expression Profiles in Pecan (Carya illinoinensis)

Salt stress severely limits the growth and ornamental value of pecan (Carya illinoinensis) in salinized regions, yet the transcriptional mechanisms underlying its stress adaptation remain unclear. In this study, a comprehensive genomic analysis of the GRAS transcription factor family identified 58 CiGRAS genes in pecan. These genes were classified into 11 subfamilies and showed conserved motifs and gene structures, with variation in promoter cis-elements suggesting diverse regulatory functions. Chromosomal distribution and duplication analysis indicated that whole-genome and dispersed duplication events were the main drivers of CiGRAS expansion. Transcriptome data revealed tissue-specific expression and strong responsiveness to salt and other stresses. Under 0.6% NaCl treatment, several CiGRAS genes were significantly upregulated, especially at 48 h. Gene co-expression analysis further highlighted GRAS-enriched modules associated with redox regulation and stress signaling. qRT-PCR validation confirmed time-specific induction of seven CiGRAS genes under salt stress. These findings provide insights into the evolutionary dynamics and stress-related roles of CiGRAS genes and offer candidate regulators for improving pecan salt tolerance in ecological greening and landscape applications.