PDF(Pubmed)
Abstract：
Inositol hexaphosphate (InsP6) is the major storage form of phosphorus in seeds. Reducing seed InsP6 content is a breeding objective in agriculture, as InsP6 negatively impacts animal nutrition and the environment. Nevertheless, how InsP6 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 InsP6 accumulation. The InsP6 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 InsP6 synthesis, and facilitate its binding and activity via phosphorylation of GRF 14-3-3 proteins. IPCKs also recruit IPK2s and PI-PLCs required for InsP4/InsP5 and InsP3 biosynthesis respectively, to form a potential IPCK-GRF-PLC-IPK2-IPK1 complex. Our findings therefore uncover a regulatory mechanism of InsP6 accumulation governed by IPCKs, shedding light on the mechanisms of InsP biosynthesis in eukaryotes.
摘要：
肌醇六磷酸（InsP6）是种子中磷的主要储存形式。降低种子InsP6含量是农业育种的目标，InsP6对动物营养和环境产生负面影响。然而，InsP6的积累是如何被调控的，在很大程度上仍然是未知的。这里,我们确定了受体样细胞质激酶（RLCKs）的进化枝，命名为肌醇多磷酸相关的细胞质激酶1-6（IPCK1-IPCK6），深入参与InsP6积累。在ipck四重（T-4m/C-4m）和五重（C-5m）突变体的种子中，InsP6浓度显着降低，伴随着磷酸盐(Pi)浓度的明显增加。质膜定位的IPCKs招募参与InsP6合成的IPK1，并通过GRF14-3-3蛋白的磷酸化促进其结合和活性。IPCK还分别招募InsP4/InsP5和InsP3生物合成所需的IPK2和PI-PLC，形成潜在的IPCK-GRF-PLC-IPK2-IPK1复合物。因此，我们的发现揭示了由IPCK控制的InsP6积累的调节机制，阐明真核生物InsP生物合成机制。
