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植物磷酸转运蛋白1(PHT1)可能是磷酸盐(Pi)吸收的唯一内流转运蛋白，在磷酸盐浓度足够高时被部分降解，以防止磷酸盐的过度积累。因此，PHT1基因的基础/组成型表达水平对于维持 Pi 摄取至关重要。 ·水稻(Oryza sativa) OsPHT1; 1是基因组中单拷贝的，因为它是高度表达的，对 Pi 没有反应; 然而，保持其基础/组成表达的机制仍不清楚。 在这里，我们通过生物化学和遗传学方法鉴定和功能研究了 OsPHT1基础/组成型表达的转录因子。 · OsWRKY21和 OsWRKY108在细胞核内相互作用，都与 OsPHT1; 1启动子的 w-box 结合。OsWRKY21或 OsWRKY108的过表达导致 Pi 积累增加，这是由于 OsPHT1表达增加引起的。 与此相反，oswrky21 oswrky108双突变体的 Pi 积累和 hspht1表达均呈 Pi 依赖性下降。此外，与 OsPHT1相似，表达 OsWRKY21-SRDX 融合蛋白(嵌合显性抑制基因)的植物在 Pi-replete 根中的 Pi 积累受到抑制，并伴有 OsPHT1的下调。 ·我们的发现表明，水稻WRKY转录因子在Pi充足的条件下通过激活OsPHT1; 1表达来冗余发挥作用来促进Pi吸收，代表了独立于中央Pi信号传导系统的新型途径。 Plant Phosphate Transporter 1 (PHT1) proteins, which are probably the only influx transporters for phosphate (Pi) uptake, are partially degraded upon sufficient Pi to prevent excessive Pi accumulation. Thus, the basal/constitutive expression level of PHT1 genes is vital for maintaining Pi uptake under Pi‐replete conditions. · Rice (Oryza sativa) OsPHT1;1 is unique since it is highly expressed and not responsive to Pi; however, the mechanism for maintaining its basal/constitutive expression remains unknown. Here, we identified and functionally characterized the transcription factors maintaining the basal/constitutive expression of OsPHT1;1 by biochemical and genetic approaches. · OsWRKY21 and OsWRKY108 interact within nucleus and both bind to the W‐box in OsPHT1;1 promoter. Overexpression of OsWRKY21 or OsWRKY108 led to increased Pi accumulation, resulting from elevated expression of OsPHT1;1. By contrast, oswrky21 oswrky108 double mutants showed decreased Pi accumulation and OsPHT1;1 expression in a Pi‐dependent manner. Moreover, similar to ospht1;1 mutants, plants expressing the OsWRKY21‐SRDX fusion protein (a chimeric dominant suppressor) were impaired in Pi accumulation in Pi‐replete root, accompanied by down‐regulation of OsPHT1;1 expression. · Our findings demonstrate that rice WRKY transcription factors function redundantly to promote Pi uptake through activating OsPHT1;1 expression under Pi‐replete conditions, representing a novel pathway independent of the central Pi signaling system. 通讯作者： Mian Gu |
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