A cryptic inhibitor of cytokinin phosphorelay controls rice grain size
A cryptic inhibitor of cytokinin phosphorelay controls rice grain size
复制标题
细胞分裂素磷酸传递的隐秘抑制剂控制水稻颗粒大小
DOI：
10.1016/j.molp.2021.09.010
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发表时间：
2022-02-07
期刊：
影响因子：
27.5
通讯作者：
Tong, Hongning
中科院分区：
文献类型：
--
作者：
Liu, Dapu;Zhao, He;Tong, Hongning
植物激素细胞分裂素通过组氨酸-天冬氨酸 (H-D) 磷酸中继发出信号来调节植物生长和发育。虽然众所周知，磷酸中继涉及组氨酸激酶、组氨酸磷酸转移蛋白（HP）和反应调节剂（RR），但外部成分如何调节这一过程仍然未知。在这里，我们证明了具有 kelch 样结构域的蛋白磷酸酶 (PPKL1)，被称为类固醇激素油菜素类固醇的信号成分，实际上是水稻 (Oryza sativa) 中细胞分裂素磷酸传递的隐秘抑制剂。 PPKL1 特定氨基酸 D364 的突变激活细胞分裂素反应，从而增大名为 s48 的半显性突变体的晶粒尺寸。含有 D364 的 PPKL1 过表达，无论是否删除磷酸酶结构域，都可以挽救 s48 突变表型。 PPKL1 与 OsAHP2（真正的 HP 之一）相互作用，D364 位于类似于 RR 接收域的区域。因此，PPKL1可以利用D364抑制OsAHP2-to-RR磷酸传递，而D364的突变则消除了这种作用。 PPKL1 的这种功能独立于油菜素类固醇信号传导所需的磷酸酶结构域。重要的是，D364 驻留区域的编辑产生了与不同的晶粒尺寸增加相关的多种半显性突变。对编辑后的植物进行进一步筛选，能够鉴定出两种能够显着提高谷物产量的基因型。总的来说，我们的研究发现了一种非典型的细胞分裂素信号抑制因子，并为种子合理设计提供了强大的工具。
Plant hormone cytokinin signals through histidine-aspartic acid (H-D) phosphorelay to regulate plant growth and development. While it is well known that the phosphorelay involves histidine kinases, histidine phosphotransfer proteins (HPs), and response regulators (RRs), how this process is regulated by external components remains unknown. Here we demonstrate that protein phosphatase with kelch-like domains (PPKL1), known as a signaling component of steroid hormone brassinosteroid, is actually a cryptic inhibitor of cytokinin phosphorelay in rice (Oryza sativa). Mutation at a specific amino acid D364 of PPKL1 activates cytokinin response and thus enlarges grain size in a semi-dominant mutant named s48. Overexpression of PPKL1 containing D364, either with the deletion of the phosphatase domain or not, rescues the s48 mutant phenotype. PPKL1 interacts with OsAHP2, one of authentic HPs, and D364 resides in a region resembling the receiver domain of RRs. Accordingly, PPKL1 can utilize D364 to suppress OsAHP2-to-RR phosphorelay, whereas mutation of D364 abolishes the effect. This function of PPKL1 is independent of the phosphatase domain that is required for brassinosteroid signaling. Importantly, editing of the D364-residential region produces a diversity of semi-dominant mutations associated with variously increased grain sizes. Further screening of the edited plants enables the identification of two genotypes that confer significantly improved grain yield. Collectively, our study uncovers a noncanonical cytokinin signaling suppressor and provides a robust tool for seed rational design.