Double fertilization in angiosperms requires the targeted delivery of immotile sperm to the eggs through pollen tubes. The polarity of tip-growing pollen tubes is maintained through dynamic association of active Rho G...Double fertilization in angiosperms requires the targeted delivery of immotile sperm to the eggs through pollen tubes. The polarity of tip-growing pollen tubes is maintained through dynamic association of active Rho GTPases of plants （ROP-GTP） with the apical plasma membrane. Guanine nucleotide exchange factors for ROPs （RopGEFs） catalyze the activation of ROPs and thereby affect spatiotemporal ROP signaling. Whereas RopGEFs have been found to be phosphorylated proteins, the kinases responsible for their phos- phorylation in v/vo and biological consequences of RopGEF phosphorylation in pollen tube growth remain unclear. We report here that the Arabidopsis AGC1.5 subfamily of cytoplasmic kinases is critical for the restricted localization of ROP-GTP during pollen tube growth. Loss of AGCI.5 and AGC1.7 functions resulted in the mistargeting of active ROPs and defective events downstream of ROP signaling in pollen tubes. AGCI.5 interacts with RopGEFs via their catalytic PRONE domain and phosphorylates RopGEFs at a conserved Ser residue of PRONE domain. Loss of AGC1.5 and AGC1.7 functions resulted in the mistargeting of RopGEFs in pollen tubes, similar to the phenotype caused by the mutation that renders RopGEFs non-phosphorylatable by AGC1.5. Collectively, our results provide mechanistic insights into the spatiotem- poral activation of ROPs during the polar growth of pollen tubes.展开更多
Summary Vacuolar trafficking routes and their regu- lators have recently drawn lots of attention in plant cell biology. A recent study reported the discovery of a plant-specific vacuolar trafficking route, i.e., a dir...Summary Vacuolar trafficking routes and their regu- lators have recently drawn lots of attention in plant cell biology. A recent study reported the discovery of a plant-specific vacuolar trafficking route, i.e., a direct ER- to-vacuole route, through analysis of VHA-a3 subcellular targeting, a key component for the tonoplast V- ATPases. Our recent findings showed that VHA-a3 targets to the tonoplast through a Rab5-mediated but Rab7-independent pathway, shedding new lights on the unconventional vacuolar trafficking route in plant cells.展开更多
基金This research was supported by the National Natural Science Foundation of China （31471304 to Y.Z. 31771558 to S.L.）, Natural Science Foundation of Shandong Province （ZR2014CM027 to S.L.）, China Postdoctoral Science Foundation （2018M632698 to E.L.）, and Research Grants Council of Hong Kong （AoE/M-05/12 and C4011-14R）. Y.Z. was partially supported by the Tai-Shan Scholar program from the Shandong Provinciak Government.
文摘Double fertilization in angiosperms requires the targeted delivery of immotile sperm to the eggs through pollen tubes. The polarity of tip-growing pollen tubes is maintained through dynamic association of active Rho GTPases of plants （ROP-GTP） with the apical plasma membrane. Guanine nucleotide exchange factors for ROPs （RopGEFs） catalyze the activation of ROPs and thereby affect spatiotemporal ROP signaling. Whereas RopGEFs have been found to be phosphorylated proteins, the kinases responsible for their phos- phorylation in v/vo and biological consequences of RopGEF phosphorylation in pollen tube growth remain unclear. We report here that the Arabidopsis AGC1.5 subfamily of cytoplasmic kinases is critical for the restricted localization of ROP-GTP during pollen tube growth. Loss of AGCI.5 and AGC1.7 functions resulted in the mistargeting of active ROPs and defective events downstream of ROP signaling in pollen tubes. AGCI.5 interacts with RopGEFs via their catalytic PRONE domain and phosphorylates RopGEFs at a conserved Ser residue of PRONE domain. Loss of AGC1.5 and AGC1.7 functions resulted in the mistargeting of RopGEFs in pollen tubes, similar to the phenotype caused by the mutation that renders RopGEFs non-phosphorylatable by AGC1.5. Collectively, our results provide mechanistic insights into the spatiotem- poral activation of ROPs during the polar growth of pollen tubes.
基金supported by Major Research Plan(2013CB945102) from the Ministry of Science,Technology of ChinaNational Natural Science Foundation of China(31261160490 to Y.Z.)Natural Science Foundation of Shandong Province(ZR2014CM027 to S.L.)
文摘Summary Vacuolar trafficking routes and their regu- lators have recently drawn lots of attention in plant cell biology. A recent study reported the discovery of a plant-specific vacuolar trafficking route, i.e., a direct ER- to-vacuole route, through analysis of VHA-a3 subcellular targeting, a key component for the tonoplast V- ATPases. Our recent findings showed that VHA-a3 targets to the tonoplast through a Rab5-mediated but Rab7-independent pathway, shedding new lights on the unconventional vacuolar trafficking route in plant cells.
