Integration of ovular signals and exocytosis of a Ca 2+ channel by MLOs in pollen tube guidance

The spatiotemporal regulation of Ca channels at the plasma membrane in response to extracellular signals is critical for development, stress response and reproduction, but is poorly understood. During flowering-plant reproduction, pollen tubes grow directionally to the ovule, which is guided by ovul...

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Published inNature plants Vol. 6; no. 2; p. 143
Main Authors Meng, Jiang-Guo, Liang, Liang, Jia, Peng-Fei, Wang, Ying-Chun, Li, Hong-Ju, Yang, Wei-Cai
Format Journal Article
LanguageEnglish
Published England 01.02.2020
Subjects
Arabidopsis - genetics
Arabidopsis - physiology
Calcium Channels - genetics
Calcium Channels - metabolism
Exocytosis - genetics
Ovule - physiology
Signal Transduction
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Summary:The spatiotemporal regulation of Ca channels at the plasma membrane in response to extracellular signals is critical for development, stress response and reproduction, but is poorly understood. During flowering-plant reproduction, pollen tubes grow directionally to the ovule, which is guided by ovule-derived signals and dependent on Ca dynamics. However, it is unknown how ovular signals are integrated with cytosolic Ca dynamics in the pollen tube. Here, we show that MILDEW RESISTANCE LOCUS O 5 (MLO5), MLO9 and MLO15 are required for pollen tube responses to ovular signals in Arabidopsis thaliana. Phenotypically distinct from the ovule-bypass phenotype of previously identified mutants, mlo5 mlo9 double-mutant and mlo5 mlo9 mlo15 triple-mutant pollen tubes twist and pile up after sensing the ovular cues. Molecular studies reveal that MLO5 and MLO9 selectively recruit Ca channel CNGC18-containing vesicles to the plasma membrane through the R-SNARE proteins VAMP721 and VAMP722 in trans mode. This study identifies members of the conserved seven transmembrane MLO family (expressed in the pollen tube) as tethering factors for Ca channels, reveals a novel mechanism of molecular integration of extracellular ovular cues and selective exocytosis, and sheds light on the general regulation of MLO proteins in cell responses to environmental stimuli.
ISSN:2055-0278