State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
New Phytol. 2014 Sep;203(4):1146-1160. doi: 10.1111/nph.12872. Epub 2014 May 28.
Despite the abundance of phosphorus in soil, very little is available as phosphate (Pi) for plants. Plants often experience low Pi (LP) stress. Intensive studies have been conducted to reveal the mechanism used by plants to deal with LP; however, Pi sensing and signal transduction pathways are not fully understood. Using in-gel kinase assays, we determined the activities of MPK3 and MPK6 in Arabidopsis thaliana seedlings under both LP and Pi-sufficient (Murashige and Skoog, MS) conditions. Using MKK9 mutant transgenic and crossed mutants, we analyzed the functions of MPK3 and MPK6 in regulating Pi responses of seedlings. The regulation of Pi responses by downstream components of MKK9-MPK3/MPK6 was also screened. LP treatment activated MPK3 and MPK6. Under both LP and MS conditions, mpk3 and mpk6 seedlings took up and accumulated less Pi than the wild-type; activation of MKK9-MPK3/MPK6 in transgenic seedlings induced the transcription of Pi acquisition-related genes and enhanced Pi uptake and accumulation, whereas its activation suppressed the transcription of anthocyanin biosynthetic genes and anthocyanin accumulation; WRKY75 was downstream of MKK9-MPK3/MPK6 when regulating the accumulation of Pi and anthocyanin, and the transcription of Pi acquisition-related and anthocyanin biosynthetic genes. These results suggest that the MKK9-MPK3/MPK6 cascade is part of the Pi signaling pathway in plants.
尽管土壤中磷的含量丰富，但植物可利用的磷酸盐（Pi）却很少。植物经常会经历低磷（LP）胁迫。已经进行了大量研究来揭示植物应对 LP 的机制；然而，Pi 感应和信号转导途径尚未完全了解。通过凝胶激酶测定，我们确定了在 LP 和 Pi 充足（Murashige 和 Skoog，MS）条件下拟南芥幼苗中 MPK3 和 MPK6 的活性。使用 MKK9 突变体转基因和杂交突变体，我们分析了 MPK3 和 MPK6 在调节幼苗 Pi 反应中的功能。还筛选了 MKK9-MPK3/MPK6 下游成分对 Pi 反应的调节。LP 处理激活了 MPK3 和 MPK6。在 LP 和 MS 条件下，mpk3 和 mpk6 幼苗比野生型吸收和积累的 Pi 更少；在转基因幼苗中激活 MKK9-MPK3/MPK6 诱导了 Pi 摄取相关基因的转录，并增强了 Pi 的吸收和积累，而其激活抑制了花青素生物合成基因的转录和花青素的积累；WRKY75 在调节 Pi 和花青素积累以及 Pi 摄取相关和花青素生物合成基因的转录时是 MKK9-MPK3/MPK6 的下游。这些结果表明，MKK9-MPK3/MPK6 级联是植物 Pi 信号通路的一部分。
