Drought is a major environmental constraint that significantly affects seedling emergence, yield, and quality of Tartary buckwheat, thereby hindering the development of its industry. However, the molecular mechanisms underlying drought tolerance genes in Tartary buckwheat remain largely unexplored. Alcohol dehydrogenase (ADH), an essential plant protein, plays a crucial role in growth, development, and stress responses; however, its specific role in drought resistance remains unclear. This study identifies an ADH gene, FtADH1, using a membership function value of drought tolerance (MFVD) combined with a genome-wide association study (GWAS) and transcriptomic profiles that confer drought tolerance in Tartary buckwheat. Our findings demonstrated that the overexpression of FtADH1 in Arabidopsis and Tartary buckwheat hairy roots enhances drought tolerance by promoting root elongation and mitigating elevated levels of reactive oxygen species (ROS). Our findings demonstrate that FtADH1 can enhance drought tolerance in Tartary buckwheat and Arabidopsis. This study identifies FtADH1 as a new regulator of Tartary buckwheat's ROS levels and stress responses, functioning by regulating protective enzyme activities at a high level to scavenge ROS and modulating root growth under drought stress. Further, it identifies proteins interacting with FtADH1 through a prokaryotic expression pull-down assay combined with mass spectrometry, revealing that FtADH1 interacts explicitly with the S-adenosyl-L-methionine (SAM) synthetase protein, FtSAMS1. Overexpression of FtSAMS1 enhances ADH enzymatic activity, leading to increased SAM content in overexpressing Tartary buckwheat hairy roots under water-deficit conditions. Additionally, overexpression of FtSAMS1 induces a drought-resistant phenotype in Arabidopsis and Tartary buckwheat hairy roots under drought stress, revealing the biological function of FtADH1. Evolutionary analysis indicates that ADH1 in Fagopyrum species has undergone significant evolutionary events, including duplication and purifying selection, which may contribute to functional diversification and adaptive advantages such as drought resistance in cultivated buckwheat. In summary, this study suggests that FtADH1 is a key contributor to drought tolerance, and its interaction with FtSAMS1 offers promising potential for developing drought-resistant varieties in Tartary buckwheat and its relative species.

Drought is becoming a common threat to crop production. Identifying and utilizing excellent drought-resistant genes is crucial to combating this stress and ensuring global food security by developing drought-resistant crop varieties. Although sugar transporters are involved in stress tolerance in many plants, the sugar transporter gene family of Tartary buckwheat has yet to be systematically analyzed. This study identified 140 sugar transporter genes from the ‘Pinku’ Tartary buckwheat genome and classified them into 10 subfamilies. Structural analysis showed that subfamily SGB/pGlcT had the highest number of introns compared to other subfamilies, and abundant abiotic stress-related cis-acting elements existed in the promoter region. Collinear analysis revealed relatively ancient genes FtSUT7, FtSTP28, FtPLT1, and FtINT2. The expression of sugar transporter genes was screened under various abiotic stresses, which revealed the association of stress tolerance with different sugar transporter genes, i.e., FtERD23, FtINT2, FtpGlcT2, and FtSTP27. Further, we observed that the overexpression of FtERD23 maintains osmotic pressure through glucose transport, which may enhance drought stress tolerance. Moreover, gene co-expression analyses using weighted gene co-expression network analysis (WGCNA) and fuzzy c-means algorithm (FCMA) identified six transcription factors that may regulate FtERD23 expression and are involved in plant drought tolerance. Our systematic analysis provides a theoretical basis for the further functional characterization of sugar transporter genes to improve drought tolerance in Tartary buckwheat and its related species.