Post-Golgi trafficking of rice storage proteins requires the small GTPase Rab7 activation complex MON1-CCZ1
Post-Golgi trafficking of rice storage proteins requires the small GTPase Rab7 activation complex MON1-CCZ1
复制标题
DOI：
10.1093/plphys/kiab175
复制
发表时间：
2021-04-19
期刊：
影响因子：
7.4
通讯作者：
Wan, Jianmin
中科院分区：
文献类型：
--
作者：
Pan, Tian;Wang, Yihua;Wan, Jianmin
蛋白质贮藏泡（PSV）是植物种子中积累贮藏蛋白的独特细胞器。虽然形态学证据表明存在多个PSV运输途径的存储蛋白靶向，调节这些过程的分子机制仍然是未知的。在这里，我们报告的功能特性的水稻（水稻）谷蛋白前体积累7（gpa 7）突变体，过度积累57 kDa谷蛋白前体在干种子。细胞学和免疫细胞化学研究表明，gpa 7突变体表现出异常积累的储存前液泡样结构，伴随着部分误定位的谷蛋白的细胞外空间。gpa 7突变体在CCZ 1基因座发生改变，该基因座编码拟南芥（Arabidopsis thaliana）钙咖啡因锌敏感性1a（CCZ 1a）和CCZ 1b的水稻同源物。生物化学证据表明，水稻CCZ 1与莫能辛敏感性1（MON 1）相互作用，这些蛋白质一起作为大鼠脑5（Rab 5）效应子和Rab 7鸟嘌呤核苷酸交换因子（GEF）发挥作用。值得注意的是，CCZ 1功能的丧失促进了液泡蛋白分选相关蛋白9（VPS 9）的内体定位，VPS 9是植物中Rab 5的GEF。总之，我们的研究结果表明，MON 1-CCZ 1复合物是通过Rab 5和Rab 7依赖的途径参与水稻贮藏蛋白的后高尔基体运输。
Protein storage vacuoles (PSVs) are unique organelles that accumulate storage proteins in plant seeds. Although morphological evidence points to the existence of multiple PSV-trafficking pathways for storage protein targeting, the molecular mechanisms that regulate these processes remain mostly unknown. Here, we report the functional characterization of the rice (Oryza sativa) glutelin precursor accumulation7 (gpa7) mutant, which over-accumulates 57-kDa glutelin precursors in dry seeds. Cytological and immunocytochemistry studies revealed that the gpa7 mutant exhibits abnormal accumulation of storage prevacuolar compartment-like structures, accompanied by the partial mistargeting of glutelins to the extracellular space. The gpa7 mutant was altered in the CCZ1 locus, which encodes the rice homolog of Arabidopsis (Arabidopsis thaliana) CALCIUM CAFFEINE ZINC SENSITIVITY1a (CCZ1a) and CCZ1b. Biochemical evidence showed that rice CCZ1 interacts with MONENSIN SENSITIVITY1 (MON1) and that these proteins function together as the Rat brain 5 (Rab5) effector and the Rab7 guanine nucleotide exchange factor (GEF). Notably, loss of CCZ1 function promoted the endosomal localization of vacuolar protein sorting-associated protein 9 (VPS9), which is the GEF for Rab5 in plants. Together, our results indicate that the MON1-CCZ1 complex is involved in post-Golgi trafficking of rice storage protein through a Rab5- and Rab7-dependent pathway.