Abstract
Xyloglucan endotransglucosylase/hydrolases (XTHs)—a family of xyloglucan modifying enzymes—play an essential role in the construction and restructuring of xyloglucan cross-links. However, no comprehensive study has been performed on this gene family in barley. A total of 24 HvXTH genes (named HvXTH1-24) and an EG16 member were identified using the recently completed genomic database of barley (Hordeum vulgare). Phylogenetic analysis showed that 24 HvXTH genes could be classified into three phylogenetic groups: (I/II, III-A and III-B) and HvXTH15 was in the ancestral group. All HvXTH protein members—except HvXTH15—had a conserved N-glycosylation site. The genomic location of HvXTHs on barley chromosomes showed that the 24 genes are unevenly distributed on the 7 chromosomes, with 10 of them specifically located on chromosome 7H. A structure-based sequence alignment demonstrates that each XTH possesses a highly conserved domain (ExDxE) responsible for catalytic activity. Expression profiles based on the barley genome database showed that HvXTH family members display different expression patterns in different tissues and at different stages. This study is the first systematic genomic analysis of the barley HvXTH gene family. Our results provide valuable information that will help to elucidate the roles of HvXTH genes in the growth and development of barley.
Highlights
Xyloglucan endotransglucosylase/hydrolases (XET/XEHs named XTHs) are a family of xyloglucan modifying enzymes that have two different catalytic activities and can act either as endotransglucosylases (XET, EC 2.4.1.207) or as endohydrolases (XEH, EC 3.2.1.151)
A total of 24 candidate HvXTHs were identified in the barley genome using data from EnsemblPlants
The details of information relating to previously reported HvXTHs is presented in Table 1 and renamed 24 predicted HvXTHs based on chromosome position
Summary
Xyloglucan endotransglucosylase/hydrolases (XET/XEHs named XTHs) are a family of xyloglucan modifying enzymes that have two different catalytic activities and can act either as endotransglucosylases (XET, EC 2.4.1.207) or as endohydrolases (XEH, EC 3.2.1.151). XTHs belong to glycoside hydrolase family 16 and play an important role in the construction and restructuring of xyloglucan cross-links [1]; their evolution has recently been studied. A previous analysis has indicated that XTHs are closely related to bacterial licheninases (EC 3.2.1.73), which hydrolyze β(1→4) linkages [4]. A later study showed that a newly identified subfamily of GH16 endo-β-glucanases from plants are an evolutionary link between bacterial licheninases and XTH genes [5].
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