Stigmatic papilla cells recover nonself pollen acceptance after self-pollen recognition
In Brassicaceae, self-incompatibility is initiated when the pollen ligand SP11/SCR activates the cognate stigma receptor kinase SRK. Although this interaction is usually considered at a single pollen-papilla interface, individual papilla cells encounter mixed pollen loads. Here, using a self-incompatibility-reconstituted Arabidopsis thaliana system, we show that self-pollen recognition…
Brassicaceae plants exhibit self-incompatibility, triggered when pollen carries a ligand called SP11/SCR that activates a specific receptor kinase in the stigma. While this interaction is typically observed at a single pollen-papilla interface, each papilla cell must handle mixed pollen loads. Using a reconstituted Arabidopsis thaliana system, researchers discovered that the recognition of self-pollen actually slows down the hydration and germination of nearby nonself pollen.
This delay is more pronounced when two self-pollen grains are present, but it diminishes when nonself pollen is introduced 2 hours after the self pollen. Repollinating after removing a self-pollen grain still showed a persistent inhibition at the initial contact site.
Live imaging using Lifeact-tdTomato revealed that self-pollination temporarily altered the orientation of F-actin within the papilla cell, subsequently returning to the normal longitudinal organization of unpollinated cells. When both self and non-self pollen were applied simultaneously, actin-bundle orientation eventually aligned with the papilla long axis before the delayed hydration of the non-self pollen.
These findings suggest that the self-recognition signaling creates a reversible, wide-ranging state that briefly limits the acceptance of compatible pollen, while local self-rejection remains at the original contact site.
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