Molecular characterization of SGR genes related to abiotic stress resistance in cotton

Stay-green (SGR) genes encode Mg‑dechelatase and play critical roles in chlorophyll degradation. Increasing evidence suggests that SGR genes also participate in abiotic stress responses, including drought and salinity tolerance, in various plant species. However, systematic identification and functional analysis of the SGR gene family in cotton ( Gossypium hirsutum ) remain limited. In this study, we performed genome‑wide identification, evolutionary characterization, and stress expression analysis of GhSGR genes. A total of six GhSGR genes were identified and were unevenly distributed across six chromosomes of the At and Dt subgenomes. Phylogenetic analysis divided these genes into SGR and SGR‑like subgroups, with conserved gene structures, protein domains, and syntenic relationships across cotton species, indicating high evolutionary conservation. Transcriptome profiling revealed that most GhSGR genes were induced by salt and PEG‑simulated drought stress. Quantitative real‑time PCR (qRT‑PCR) further confirmed that GhSGR1 and GhSGR3 exhibited distinct, dynamic expression patterns under stress treatments. Co‑expression network analysis suggested that GhSGR genes are co‑expressed with stress‑related transporters and transcription factors, suggesting potential involvement in stress regulation. These results demonstrate that GhSGR genes are highly conserved during evolution and are involved in the response to salt and drought stress in cotton. This study provides key candidate genes and a theoretical basis for further functional dissection and molecular breeding of stress resistance in cotton.