Overexpression of Myb-Like Transcription Factor Simyb30 from Foxtail Millet (Setaria Italica L.) Confers Tolerance to Low Nitrogen Stress in Transgenic Rice

Abstract

Nitrogen fertilizers significantly increase crop yields; however, the effect of excessive nitrogen fertilizer use on the environment and soil requires urgent attention. Improving crop nitrogen use efficiency is crucial to augment the yield and protect the environment. Foxtail millet (Setaria italica L.), a gramineous crop with significant tolerance to barren environments, is a model crop for studying abiotic stress resistance in gramineous crops. However, the knowledge of the regulatory network for nitrogen use efficiency in foxtail millet remains limited. In this study, we identified an R2R3-like MYB transcription factor of foxtail millet, SiMYB30, which belongs to the MYB subfamily 17. The expression of SiMYB30 is responsive to low nitrogen (LN) and abscisic acid (ABA). Compared with wild-type (WT) Kitaake, rice overexpressing SiMYB30 significantly increased shoot fresh weight, shoot dry weight, and plant height at the seedling stage under LN treatment indoors. Concordantly, overexpression of SiMYB30 in field experiments significantly increased grain nitrogen content and grain yield per plant in rice. Furthermore, quantitative PCR (qPCR) experiments revealed that SiMYB30 could activate the expression of nitrogen uptake-related genes, OsNRT1, OsNRT1.1B, and OsNPF2.4, and the assimilation-related genes, OsGOGAT1, OsGOGAT2, and OsNIA2. Notably, SiMYB30 directly binds to the promoter of OsGOGAT2 and regulates its expression. These results highlight the novel and pivotal role of SiMYB30 in improving the nitrogen use efficiency of crops.

Keywords: foxtail millet, low nitrogen, MYB like transcription factor, nitrogen use efficiency, transgenic rice