Enhanced salt stress tolerance in transgenic potato plants expressing IbMYB1, a sweet potato transcription factor

Abstract

IbMYB1, a transcription factor (TF) for R2R3-type MYB TFs, is a key regulator of anthocyanin biosynthesis during storage of sweet potatoes. Anthocyanins provide important antioxidants of nutritional value to humans, and also protect plants from oxidative stress. This study aimed to increase transgenic potatoes' (Solanum tuberosum cv. LongShu No.3) tolerance to environmental stress and enhance their nutritional value. Transgenic potato plants expressing IbMYB1 genes under the control of an oxidative stress-inducible peroxidase (SWPA2) promoter (referred to as SM plants) were successfully generated through Agrobacterium-mediated transformation. Two representative transgenic SM5 and SM12 lines were evaluated for enhanced tolerance to salinity, UV-B rays, and drought conditions. Following treatment of 100 mM NaCl, seedlings of SM5 and SM12 lines showed less root damage and more shoot growth than control lines expressing only an empty vector. Transgenic potato plants in pots treated with 400 mM NaCl showed high amounts of secondary metabolites, including phenols, anthocyanins, and flavonoids, compared with control plants. After treatment of 400 mM NaCl, transgenic potato plants also showed high DDPH radical scavenging activity and high PS II photochemical efficiency compared with the control line. Furthermore, following treatment of NaCl, UV-B, and drought stress, the expression levels of IbMYB1 and several structural genes in the flavonoid biosynthesis such as CHS, DFR, and ANS in transgenic plants were found to be correlated with plant phenotype. The results suggest that enhanced IbMYB1 expression affects secondary metabolism, which leads to improved tolerance ability in transgenic potatoes.