The ArabidopsisSNAREcomplex genes regulate the early stages of pollen-stigma interactions

Abstract

In the Brassicaceae, the process of accepting compatible pollen is a key step in successful reproduction and highly regulated following interactions between the pollen and the stigma. Central to this, is the initiation of secretion in the stigma, which is proposed to provide resources to the pollen for hydration and germination and pollen tube growth. Previously, the eight exocyst subunit genes were shown to be required in the Arabidopsis stigma to support these pollen responses. One of the roles of the exocyst is to tether secretory vesicles at the plasma membrane for membrane fusion by the SNARE complex to enable vesicle cargo release. Here, we investigate the role of ArabidopsisSNAREgenes in the stigma for pollen responses. Using a combination of different knockout and knockdownSNAREmutant lines, we show thatVAMP721, VAMP722, SYP121, SYP122andSNAP33are involved in this process. Significant disruptions in pollen hydration were observed following pollination of wildtype pollen on the mutantSNAREstigmas. Overall, these results place the Arabidopsis SNARE complex as a contributor in the stigma for pollen responses and reaffirm the significance of secretion in the stigma to support the pollen-stigma interactions.Key MessageThe VAMP721, VAMP722, SYP121, SYP122 and SNAP33 SNAREs are required in the Arabidopsis stigma for pollen hydration, further supporting a role for vesicle trafficking in the stigma’s pollen responses.