Overexpression of OsMYB4P, an R2R3-type MYB transcriptional activator, increases phosphate acquisition in rice

• We isolated and characterized novel OsMYB4P, rice R2R3 MYB transcription factor, in phosphate responses.
• The function of OsMYB4P is a transcriptional activator in plants.
• Transcriptional expression of OsMYB4P increased in response to nutrient deficiency stress.
• Overexpression of OsMYB4P enhanced plant growth and root system architecture.
• OsMYB4P regulates Pi accumulation and expression of Pi-responsive transporters in rice.

R2R3 MYB transcription factors play regulatory roles in plant responses to various environmental stresses and nutrient deficiency. In this study, we isolated and designated OsMYB4P, an R2R3 MYB transcription factor, from rice (Oryza sativa L. ‘Dongjin’) under phosphate-deficient conditions. OsMYB4P was localized in the nucleus and acted as a transcriptional activator. Transcriptional levels of OsMYB4P in cell suspension, shoots, and roots of rice increased under phosphate-deficient conditions. Shoots and roots of OsMYB4P-overexpressing plants grew well in high- and phosphate-deficient conditions. In addition, root system architecture was altered considerably as a result of OsMYB4P overexpression. Under both phosphate-sufficient and -deficient conditions, more Pi accumulated in shoots and roots of OsMYB4P-overexpressing plants than in the wild type. Overexpression of OsMYB4P led to greater expression of Pi transporter-family proteins OsPT1, OsPT2, OsPT4, OsPT7, and OsPT8 in shoots, and to decreased or unchanged expression of these proteins in roots, with the exception of OsPT8. These results demonstrate that OsMYB4P may be associated with efficient utilization of Pi in rice through transcriptional activation of Pi homeostasis-related genes.