Abstract
The self-incompatibility (SI) system of the plant species Brassica is controlled by the S-locus, which contains SRK and SP11. SP11 binding to SRK induces SRK autophosphorylation and initiates a signaling cascade leading to the rejection of self-pollen. However, the mechanism controlling hydration and germination arrest during self-pollination is unclear. We observed the concentration of actin bundles at the cross-pollen attachment site and actin reorganization and likely depolymerization at self-pollen attachment site by cytological staining and monitoring transiently expressed GFP-mTalin. The actin-depolymerizing drug cytochalasin D significantly inhibited pollen hydration and germination during cross-pollination. Additionally, UHV-EM tomography revealed the close association of the actin cytoskeleton with an apical vacuole network. Self-pollination disrupted the vacuole network while cross-pollination led to vacuolar rearrangements toward the site of pollen attachment. Taken together, our data suggest that self- and cross-pollination differentially affect the dynamics of actin cytoskeleton leading to changes in vacuolar structure associated with hydration and germination.
