Genome-wide identification and gene expression analysis of the polysaccharide lyase (PL) gene family in soybean (Glycine max)

Soybean ( Glycine max ) is an important oil crop, and its growth is severely inhibited by abiotic stresses such as salt, cadmium, selenium, and manganese. Polysaccharide lyase (PL) can participate in regulating the cell wall remodeling induced by stress and bind cations (such as Na⁺, Ca²⁺, Cd²⁺) to the cell wall. Although studies have confirmed the regulatory roles of PL genes such as Cicer arietinum ( Ca31032 ) and Avicennia marina ( AmPL ) under salt and cadmium stress, there is currently no report on a systematic whole-genome study of the soybean PL gene family. In this study, the soybean PL gene family under manganese (Mn), cadmium (Cd), salt (NaCl), and selenium (Se) stresses using genome-wide identification and qRT-PCR expression analysis were investigated. A total of 48 GmPL family members were identified in the soybean genome. These genes showed markedly divergent physicochemical properties, uneven distribution across 18 chromosomes, and expansion mediated by segmental and tandem duplications. Phylogenetic analysis divided the GmPL family into three subfamilies, with members within the same subfamily generally sharing similar gene structures and conserved motifs. Cis -acting element analysis indicated that GmPL promoters were enriched in light-responsive, hormone-regulatory, and stress-responsive elements. Under the four abiotic stresses, nine representative GmPL genes exhibited tissue- and stress-specific expression patterns: GmPL3 and GmPL30 were significantly up-regulated in roots under Mn and Cd stresses; GmPL9 and GmPL35 showed the strongest induction in roots under salt stress; and GmPL3 , GmPL18 , GmPL30 , and GmPL39 were co-induced in leaves under Se treatment. Protein-protein interaction network analysis indicated that GmPL30 occupied a central hub position, whereas GmPL39 was positioned at the network periphery. GO and KEGG enrichment analyses indicated that the GmPL family was mainly associated with pectin catabolism, carbon-oxygen lyase activity, and pentose and glucuronic acid interconversion pathways. This study clarifies the regulatory roles of the soybean PL gene family under multiple abiotic stresses and highlights the potential importance of GmPL3 , GmPL30 , GmPL9 , and GmPL35 in stress responses. These findings improve our understanding of PL-mediated cell wall remodeling and ion sequestration and provide potential molecular targets and a theoretical basis for improving soybean abiotic stress resistance through genetic engineering.