Genome-wide association analysis locates FtAUR3 in Tartary buckwheat that contributes to enhance plant salt resistance

Tartary buckwheat (Fagopyrum tataricum), an underutilized pseudocereal, possesses significant nutritional and pharmaceutical properties and demonstrates resistance to drought and nutrient deficiency. However, this environmentally sustainable crop exhibits sensitivity to salt stress, which can induce water loss, stomatal closure, impair photosynthesis and metabolism, and diminish yield and quality of Tartary buckwheat. Understanding the mechanisms of salt stress tolerance in buckwheat is therefore crucial. This study identified a locus containing 35 candidate genes on chromosome 2 that shows significant association with salt tolerance of Tartary buckwheat through genome-wide association analysis (GWAS). Transcriptome analysis demonstrated that the serine/threonine-protein kinase Aurora-3 (FtAUR3) family gene exhibited upregulation in response to salt stress. A single nucleotide deletion in the FtAUR3 promoter results in elevated FtAUR3 expression and enhanced salt tolerance in Tartary buckwheat. Overexpression of FtAUR3 in buckwheat hairy roots promotes the accumulation of flavonoids, including rutin and cinnamic acid, while inducing the expression of flavonoid biosynthesis genes, such as PAL, C4H, F3H, and F3´H, under salt stress. Additionally, overexpression of FtAUR3 in Arabidopsis thaliana induced the expression of salt-resistant genes (salt-resistant genes (SOS1), AVP1, etc.) and enhanced salt tolerance compared to wild type plants. Under salt stress, FtAUR3 significantly enhances the levels of reactive oxygen species pathway components, including superoxide dismutase, catalase, and peroxidase, thereby improving plant salt tolerance. The study demonstrated that FtAUR3 interacts with the critical enzyme FtGAPB in the reactive oxygen species (ROS) pathway, suggesting a potential mechanism through which FtAUR3 contributes to ROS signaling. These findings indicate that FtAUR3 plays a crucial positive role in Tartary buckwheat resistance against salt stress.