Functional activation of a novel R2R3-MYB protein gene, GmMYB68, confers salt-alkali resistance in soybean (Glycine max L.)

Soil salinity significantly reduces soybean (Glycine max L.) production worldwide. Plants resistance to stress conditions is a complex characteristic regulated by multiple signaling pathways. The v-Myb avian myeloblastosis viral oncogene homolog (MYB) transcription factor (TF) plays a crucial role in plant development, secondary metabolism, and abiotic stress responses. GmMYB68-overexpression and RNA interference (RNAi) lines were established for examining the function of G. max GmMYB68 in plant responses to abiotic stresses. The predicted amino acid sequence of GmMYB68 was similar to that of R2R3-MYB proteins. Quantitative real-time PCR analysis revealed that GmMYB68 expression varied in response to abiotic stresses. GmMYB68-overexpression lines showed enhanced resistance to salt and alkali stresses and their osmotic adjustment and photosynthetic rates were also stronger than that of GmMYB68-RNAi and wild type plants. Although wild type and transgenic plants showed no significant differences in agronomic traits under normal conditions, the overexpression of GmMYB68 increased grain number and 100-grain weights under salt stress. Our study identified a valuable TF associated with stress response in soybean, as its overexpression might help improve salt and alkali tolerance in soybean and other crops.