Background: Xyloglucan endotransglucosylase/hydrolases (XTHs) are a class of cell wall-associated enzymes involved in the construction and remodeling of cellulose/xyloglucan crosslinks. However, knowledge of this gene family in the model monocot Brachypodium distachyon is limited.
Results: A total of 29 BdXTH genes were identified from the reference genome, and these were further divided into three main groups (Group I/II, Group III, and the Ancestral Group) through comparative phylogenetic analysis. Gene structure and protein motif analysis indicate that closely clustered BdXTH genes are relatively conserved within each group. A highly conserved amino acid domain (DEIDFEFLG) responsible for catalytic activity was identified in all BdXTH proteins. We detected three pairs of segmentally duplicated BdXTH genes and five groups of tandemly duplicated BdXTH genes, which have played important roles in the expansion of the BdXTH gene family. Cis -elements related to hormones, growth, and abiotic stress responses were identified in the promoters of each BdXTH gene. Most BdXTH genes have distinct expression patterns in different tissues and growth stages. Furthermore, when roots were treated with two abiotic stresses (salinity and drought) and four plant hormones (IAA, auxin; GA3, gibberellin; ABA, abscisic acid and BR, brassinolide), the expression levels of many BdXTH genes changed significantly, suggesting possible roles in response to various environmental stimuli and plant hormones.
Conclusion: In this study, we performed genome-wide identification, characterization, and expression pattern analysis of the XTH gene family in Brachypodium, which provide valuable information for further elucidation of the biological functions of BdXTH genes in the model grass B. distachyon.