Physiological and FtCHS Gene Expression Responses to PEG-Simulated Drought and Cadmium Stresses in Tartary Buckwheat Seedlings

Drought and heavy metal contaminated soil has become one of the main factors affecting the sustainable development of agricultural production and the ecological environment. Tartary buckwheat is rich in flavonoids and has a high tolerance to barren land and harsh environments. Chalcone synthase (CHS) is the key enzyme in the flavonoid biosynthesis pathway, and its gene expression is regulated by tissue development and abiotic stress. In this experiment, a tartary buckwheat variety named Xiqiao 2 was used as the experimental material to analyze the physiological characteristics of seedlings and to clone the CHS gene and analyze the expression in tartary buckwheat leaves under drought and cadmium (Cd) stress. The results showed that drought and Cd stress significantly reduced root vigor but increased the activity of peroxidase (POD) and superoxide dismutase (SOD) and the content of malondialdehyde (MDA), soluble sugar, soluble protein and proline in buckwheat seedlings. A 1188 bp FtCHS gene encoding 391 amino acid residues was cloned. The expression of the FtCHS gene in tartary buckwheat increased rapidly under Cd stress, reaching a maximum at 3 h that was approximately 20 times that of the control group (0 h). The expression of the FtCHS gene decreased rapidly under drought stress; the expression level was very low within 12 h, and the change was not significant, while the increase was obvious at 12–48 h. This result indicated that the FtCHS gene actively responded to Cd stress in a short amount of time and had relatively stable adaptability to drought stress. This study provides a theoretical basis for further research on the functional characteristics of the FtCHS gene and its molecular mechanism in tartary buckwheat under abiotic stresses such as drought and soil heavy metal pollution.