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Overexpression of MYB4p enhance phosphate acquisition and increase Pi content in rice
The molecuar prossing of upsteam regulation of Pi response genes during Pi starvation remains inadequately understood. 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 under low-phosphate 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 low phosphate conditions. To investigate the function of OsMYB4P in Pi-starvation signaling, we developed transgenic rice plants overexpressing OsMYB4P for analysis of Pi signaling and uptake. Shoots and roots of OsMYB4P overexpressing plants grew well in high and low phosphate 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 lead to Pi accumulation and acts as a Pi-dependent regulator in controlling the expression of Pi transporters.
