Betula platyphylla glucosyltransferase BpGT14;6 is essential for cell wall development and stress response

Glycosyltransferases (GTs) constitute a diverse family of synthetic polysaccharides with important roles in plant growth and development. This study characterized the GT14 family gene BpGT14;6 of birch (Betula platyphylla Suk.). BpGT14;6 was highly expressed in the xylem and stem of birch plants. Subcellular localization analysis suggested that BpGT14;6 was located in the Golgi apparatus. RNA interference (RNAi) silencing of BpGT14;6 revealed lower lignin, hemicellulose, and pectin contents compared to wild type (WT) plants. Following treatment with abscisic acid (ABA), compared to WT plants, RNAi-BpGT14;6 plants were more sensitive to ABA, suffered more membrane lipid damage, and accumulated more reactive oxygen species. The inhibition of BpGT14;6 expression narrowed the birch xylem and thinned the cell wall, and increased the expression of multiple ABA pathway-related genes in birch under ABA treatment. Compared to WT plants, RNAi-BpGT14;6 plants showed increased tolerance to drought stress. Promoter analysis revealed that BpGT14;6 is involved in hormone regulation and adaptation to adversity. Using the 1156 bp BpGT14;6 promoter as bait, two potential transcription factors, BpWRKY1 and BpARF2, were identified through Y1H screening that may regulate its expression. EMSA confirmed that BpWRKY1 and BpARF2 can directly bind to the W-BOX and AuxRE cis-acting elements on the BpGT14;6 promoter, respectively. The collective results suggest that BpGT14;6 affects birch xylem and cell wall development by affecting lignin, hemicellulose, and pectin synthesis, and participates in birch adversity adaptation.