Comprehensive genome-wide study of Glutaredoxin (GRX) gene family in the liverwort Marchantia polymorpha and exploring their roles in abiotic stress tolerance

Glutaredoxins (GRXs) are thiol-disulfide oxidoreductases that function as key regulators of redox homeostasis, development, and stress responses in plants. Despite their functional importance, little is known about the GRX gene family in early diverging land plants. In this study, we performed a comprehensive genome-wide identification of GRX genes in the liverwort Marchantia polymorpha and their role in abiotic stresses. A total of 17 MpGRX genes with 2 isoforms (19 MpGRX) containing the conserved Glutaredoxin domain (PF00462) were identified using BLAST, HMMER, and SMART approaches. Gene structure analysis revealed that six MpGRX genes contained a single intron, whereas the remaining genes exhibited more complex structures with three or more introns, suggesting gene expansion and functional diversification. Evolutionary analysis was conducted using non-synonymous (Ka) and synonymous (Ks) substitution rates between MpGRX genes and homologous genes from Physcomitrella patens, Ceratopteris richardii, Pinus taeda, Arabidopsis thaliana, and Oryza sativa. The results indicated generally low Ka values, except in one MpGRX–PtGRX pair with Ka = 1.59, suggesting potential functional divergence in gymnosperms. Ks-based divergence time estimates were consistent with known evolutionary separations. Selection pressure analysis based on Ka/Ks ratios revealed that most GRX gene pairs were under purifying selection, particularly those between M. polymorpha and mosses, ferns, and angiosperms.

This study provides novel insights into the structural diversity, evolutionary history, and selective constraints acting on the GRX gene family in M. polymorpha, offering a foundation for future functional and comparative studies in early land plant lineages.