Role of PtrXTH1 and PnXTH1 Genes Encoding Xyloglucan Endo-Transglycosylases in Regulation of Growth and Adaptation of Plants to Stress Factors

The expression level of the gene PtrXTH1 encoding xyloglucan endo-transglycosylase in the leaves of Populus tremula L. of wild-type and in response to exogenous phytohormones treatment was analyzed. The highest level of transcripts of PtrXTH1 was detected in young, intensively growing leaves of aspen. In young aspen leaves, the expression of PtrXTH1 was induced by cytokinins, auxins, and brassinosteroids. The content of PtrXTH1 transcripts increased under the constitutive expression of the PnARGOS-LIKE gene. Bioinformatic analysis of PtXTH1 putative promoter region in P. trichocarpa Torr. and A. Gray ex. Hook showed the presence of cis-regulatory elements associated with the regulation of growth and stress resistance. To determine the role of the gene under study, we also created transgenic tobacco plants with constitutive expression of the PnXTH1 gene (the ortholog of PtrXTH1 from the black poplar P. nigra). Transgenic tobacco plants were characterized by an increase in leaf size and fresh and dry weight of the aboveground part under normal growth conditions. When grown under conditions of salinization and drought, transgenic plants were distinguished by increased stress resistance due to the maintenance of cell expansion in roots and stems at a higher level and the ability to more effectively retain water in leaves compared with wild-type plants.