Characterization of the XTH Gene Family: New Insight to the Roles in Soybean Flooding Tolerance

Abstract

Xyloglucan endotransglycosylases/hydrolases (XTHs) are a class of enzymes involved in the construction and remodeling of cellulose/xyloglucan crosslinks and play an important role in regulating cell wall extensibility. However, little is known about this class of enzymes in soybean. Here, 61 soybean <i>XTH</i> genes (<i>GmXTH</i>s) were identified and classified into three subgroups through comparative phylogenetic analysis. Genome duplication greatly contributed to the expansion of <i>GmXTH</i> genes in soybean. A conserved amino acid motif responsible for the catalytic activity was identified in all GmXTHs. Further expression analysis revealed that most <i>GmXTHs</i> exhibited a distinct organ-specific expression pattern, and the expression level of many <i>GmXTH</i> genes was significantly associated with ethylene and flooding stress. To illustrate a possible role of <i>XTH</i> genes in regulating stress responses, the <i>Arabidopsis</i><i>AtXTH31</i> gene was overexpressed in soybean. The generated transgenic plants exhibited improved tolerance to flooding stress, with a higher germination rate and longer roots/hypocotyls during the seedling stage and vegetative growth stages. In summary, our combined bioinformatics and gene expression pattern analyses suggest that <i>GmXTH</i> genes play a role in regulating soybean stress responses. The enhanced soybean flooding tolerance resulting from the expression of an <i>Arabidopsis</i> XTH also supports the role of <i>XTH</i> genes in regulating plant flooding stress responses.