Genome-wide identification and expression analysis of the GT31 gene family in Larix kaempferi

β-(1,3)-galactosyltransferase can catalyze the formation of β-(1,3)-Gal linkage, which plays an important role in the biosynthesis of plant polysaccharides or glycoproteins. The xylem of larch contains a large amount of arabinogalactan, but the regulation of its biosynthesis has not been reported. In this study, galactosyltransferase 31 family was identified from the genome of Larix kaempferi by bioinformatics methods, and the phylogenetic evolution, gene structure, promoter cis-elements, and expression patterns were also analyzed. A total of 14 members of the LkGT31 family with complete domain were identified, encoding 312–685 amino acids, and their molecular weights ranged from 35.21 to 78.07 kDa. Evolutionary relationships indicate that 14 LkGT31s can be divided into three clades (clade 1, clade 7, and clade 10). Most of the LkGT31s promoter region contained light responsive elements, ABA responsive elements (ABRE), and stress responsive elements (STRE). The results of qRT-PCR showed that most LkGT31s were highly expressed in stems. All LkGT31s were able to produce varying degrees of reaction under ABA treatment, among which LkGalT6 and LkGalT12 were the highest. Yeast two-hybrid (Y2H) and luciferase complementation imaging assay (LCI) showed that LkGalT14 could form homodimers. Taken together, these findings will help to study the function of LkGT31s and lay a foundation for the regulation mechanism of arabinogalactan synthesis.