Transcriptome-wide characterization and functional analysis of Xyloglucan endo-transglycosylase/hydrolase (XTH) gene family of Salicornia europaea L. under salinity and drought stress

Background Salicornia europaea is a halophyte that has a very pronounced salt tolerance. As a cell wall manipulating enzyme, xyloglucan endotransglycosylase/hydrolase (XTH) plays an important role in plant resistance to abiotic stress. However, no systematic study of the XTH gene family in S. europaea is well known. PacBio Iso-Seq transcriptome sequence data were used for bioinformatics and gene expression analysis using real-time quantitative polymerase chain reaction (RT-qPCR). Results Transcriptome sequencing (PacBio Iso-Seq system) generated 16,465,671 sub-reads and after quality control of Iso-Seq, 29,520 isoforms were obtained with an average length of 2112 bp. A total of 24,869 unigenes, with 98% of which were obtained using coding sequences (CDSs), and 6398 possible transcription factors (TFs) were identified. Thirty-five (35) non-redundant potential SeXTH proteins were identified in S. europaea and categorized into group I/II and group III based on their genetic relatedness. Prediction of the conserved motif revealed that the DE(I/L/F/V)DF(I)EFLG domain was conserved in the S. europaea proteins and a potential N-linked glycosylation domain N(T)V(R/L/T/I)T(S/K/R/F/P)G was also located near the catalytic residues. All SeXTH genes exhibited discrete expression patterns in different tissues, at different times, and under different stresses. For example, 27 and 15 SeXTH genes were positively expressed under salt stress in shoots and roots at 200 mM NaCl in 24 h, and 34 SeXTH genes were also positively regulated under 48 h of drought stress in shoots and roots. This indicates their function in adaptation to salt and drought stress. Conclusion The present study discovered SeXTH gene family traits that are potential stress resistance regulators in S. europaea, and this provides a basis for future functional diversity research.