LAUSR

Successful reproduction in the Brassicaceae is mediated by a complex series of interactions between the pollen and the pistil, and some species have an additional layer of regulation with the self-incompatibility trait. While the initial activation of the self-incompatibility pathway by the pollen S-locus protein 11/S locus cysteine-rich protein and the stigma S Receptor Kinase is well characterized, the downstream mechanisms causing self-pollen rejection are still not fully understood. In previous studies, we detected the presence of autophagic bodies with self-incompatible pollinations in Arabidopsis lyrata and transgenic A. thaliana lines, but whether autophagy was essential for self-pollen rejection was unknown. Here, we investigated the requirement of autophagy in this response by crossing mutations in the essential AUTOPHAGY7 (ATG7) and ATG5 genes into two different transgenic self-incompatible A. thaliana lines in the Col-0 and C24 accessions. By using these previously characterized transgenic lines that express A. lyrata and A. halleri self-incompatibility genes, we demonstrated that disrupting autophagy weakened their self-incompatible responses in the stigma. When the atg7 or atg5 mutations were present, an increased number of self-incompatible pollen were found to hydrate and form pollen tubes that successfully fertilized the self-incompatible pistils. Additionally, we confirmed the presence of GFP-ATG8a-labelled autophagosomes in the stigmatic papillae following self-incompatible pollinations. Together, these findings support the requirement of autophagy in the self-incompatibility response and add to the growing understanding of the intracellular mechanisms employed in the transgenic A. thaliana stigmas to reject self-pollen.