State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China.
Guangdong Laboratory for Lingnan Modern Agriculture, College of Natural Resources and Environment, South China Agricultural University, 5100642, Guangzhou, China.
Nat Commun. 2024 Jun 14;15(1):5107. doi: 10.1038/s41467-024-49102-6.
Inositol hexaphosphate (InsP) is the major storage form of phosphorus in seeds. Reducing seed InsP content is a breeding objective in agriculture, as InsP negatively impacts animal nutrition and the environment. Nevertheless, how InsP accumulation is regulated remains largely unknown. Here, we identify a clade of receptor-like cytoplasmic kinases (RLCKs), named Inositol Polyphosphate-related Cytoplasmic Kinases 1-6 (IPCK1-IPCK6), deeply involved in InsP accumulation. The InsP concentration is dramatically reduced in seeds of ipck quadruple (T-4m/C-4m) and quintuple (C-5m) mutants, accompanied with the obviously increase of phosphate (Pi) concentration. The plasma membrane-localized IPCKs recruit IPK1 involved in InsP synthesis, and facilitate its binding and activity via phosphorylation of GRF 14-3-3 proteins. IPCKs also recruit IPK2s and PI-PLCs required for InsP/InsP and InsP biosynthesis respectively, to form a potential IPCK-GRF-PLC-IPK2-IPK1 complex. Our findings therefore uncover a regulatory mechanism of InsP accumulation governed by IPCKs, shedding light on the mechanisms of InsP biosynthesis in eukaryotes.
肌醇六磷酸（InsP）是种子中磷的主要储存形式。降低种子中的 InsP 含量是农业中的一个育种目标，因为 InsP 会对动物营养和环境产生负面影响。然而，InsP 积累的调节机制在很大程度上仍然未知。在这里，我们鉴定了一组受体样细胞质激酶（RLCKs），命名为肌醇多磷酸相关细胞质激酶 1-6（IPCK1-IPCK6），它们深度参与 InsP 积累。ipck 四重（T-4m/C-4m）和五重（C-5m）突变体种子中的 InsP 浓度显著降低，同时磷酸盐（Pi）浓度明显增加。定位于质膜的 IPCKs 募集参与 InsP 合成的 IPK1，并通过磷酸化 GRF 14-3-3 蛋白促进其结合和活性。IPCKs 还募集分别参与 InsP/InsP 和 InsP 生物合成所需的 IPK2s 和 PI-PLCs，形成潜在的 IPCK-GRF-PLC-IPK2-IPK1 复合物。因此，我们的研究结果揭示了由 IPCKs 控制的 InsP 积累的调节机制，为真核生物的 InsP 生物合成机制提供了新的认识。
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