Genome-wide identification and expression analysis of the GARP superfamily in response to abiotic stresses in alfalfa (Medicago sativa L.)

In this study, a total of 51 GARP genes (referred to as MsGARPs) were identified from the alfalfa reference genome (Zhongmu No. 1) and renamed on the basis of their chromosomal distribution (MsARR-B1 to MsARR-B20 and MsGLK1 to MsGLK31). These MsGARP proteins were phylogenetically classified into 5 subfamilies, ARR-B, GLK, NIGT1/HRS1/HHO, PHR1/PHL1 and KAN.​ Gene structure and conserved motif analyses revealed motif 1 (B-motif) being universally conserved across all MsGARP members. Collinearity analysis detected 5 tandem and 7 segmental duplication events. Transcriptomic data demonstrated tissue-specific expression of MsARR-B20 and widespread expression of 32 MsGARP genes across various tissues. Further analysis revealed that all MsGLK genes responded to drought, salt, and cold stress. Additionally, MsGLK6, MsGLK17, MsGLK21 and MsGLK23 exhibited significant differential expression in response to phosphate stress in both roots and shoots of alfalfa, with their expression induced under phosphate deficiency, highlighting their pivotal roles in adaptation to phosphorus starvation in alfalfa.​ CONCLUSION: The study provides the first systematic characterization of the MsGARP superfamily in alfalfa, elucidating their evolutionary dynamics and stress-responsive profiles. These findings lay a foundation for the functional dissection of MsGARP genes in abiotic stress adaptation, particularly phosphorus starvation, and offer insights for the breeding of stress-tolerant alfalfa varieties.