Genome-wide Identification and Expression Analysis of the Eyloglucan Endotransglucosylase/hydrolase Gene Family in Poplar

Background: Xyloglucan endotransglucosylase/hydrolase (XTH) plays an important role in the process of plant cell wall reconstruction, and also involved in plants stress resistance. However, its characteristics of XTH family genes have not been reported in poplar. Results: : In this study, we found 43 PtrXTH genes from Populus simonii × Populus nigra , and most of them contain two conserved structures (Glyco_hydro_16 and XET_C domain). The promoter regions of the PtrXTH genes contain many cis-acting elements related to growth and development and adverse stresses responses. Collinearity analysis revealed that the XTH family from poplarhave an evolutionary relationship with other five species, including Eucalyptus robusta , Solanum lycopersicum , Glycine max , Arabidopsis , Zea mays and Oryza sativa . Through RNA-Seq analysis, we found that the PtrXTH genes have different expression patterns in the roots, stems and leaves, and many of them are highly expressed in the roots. In addition, we found 11 differentially expressed PtrXTH genes in the roots, 9 in the stems, and 7 in the leaves under salt stress, and verified the accuracy of RNA-Seq analysis by RT-qPCR. Conclusion: All the results indicated that XTH family genes may play an important role in tissue specificity and salt stress response. This study laid a theoretical foundation for further study on the functions of XTH genes in poplar.