Pollen PCP-B peptides unlock a stigma peptide–receptor kinase gating mechanism for pollination (Science)

It’s spring where I live and the air and my eyes are filled with pollen. The lucky few pollen grains that land on the stigmatic surface of a flower might germinate and deliver the sperm to the ovule, but there are many checkpoints even after their safe landing. Here, Liu et al. uncover one of the earliest tests that must be passed for pollen to germinate. Previous studies have shown an important role for small peptides as signals during pollination. In this new work, the authors found that one of these is necessary for pollen to hydrate on the stigmatic surface. They showed that the peptide produced by the pollen competes with a stigma-produced peptide for biding to a receptor-like kinase. When the pollen peptide binds, levels of reactive oxygen species in the stigma drop, allowing the pollen to hydrate, moving one step closer to successful fertilization. (Summary by Mary Williams @PlantTeaching) Science  10.1126/science.abc6107