ing a defense response to powdery mildew fungal infection. With B. napus compatible pollinations, the fusion of the MVBs with the Varlitinib papillar plasma membrane would result in the release of the internal vesicles into the apoplastic space. By 20 min post-compatible pollination, a buildup of exosome-like structures could be observed between the papillar plasma membrane and the cell wall under the pollen grain. Interestingly, the release of exosomes does offer an explanation for the previously published work by Elleman & Dickinson where they treated B. oleracea stigmatic papillae for 20 min with coating extracted from compatible pollen, and observed vesicle-like structures within the expanded papillar cell wall. Elleman & Dickinson also observed that these vesicle-like structures appeared to be fusing under the papillar cuticle to release their contents. For both the self-incompatible pollinations using A. lyrata or B. napus W1, the vesicles/MVBs were absent from the stigmatic papillar membrane under the pollen grain. From our model, we had predicted that the self-incompatibility pathway would block the basal pollen recognition pathway through ARC1’s inhibition of Exo70A1 would prevent vesicle/MVB secretion at the papillar plasma membrane. One possible outcome from this would be that the self-incompatible pollinated stigmatic papilla would appear like an exocyst mutant with the 
accumulation of vesicles/MVBs in the cytoplasm. For example, this was observed for the pollinated A. thaliana exo70A1 and B. napus Westar Exo70A1 RNAi stigmatic papillae. However, the selfincompatibility response in both A. lyrata and B. napus W1 appeared to go one step further and target vesicles/MVBs to the vacuole for degradation. This was clearly seen 21821671 for the B. napus W1 stigmatic papillae where the MVBs were found inside the vacuole at 10 min post-self-incompatible pollination. For A. lyrata, vesicles could not be observed in the vacuole; however, dense material was found to accumulate 20571074 in the vacuole at 10 min post-self-incompatible pollination. Pre-treatment with the E-64 cysteine protease inhibitor, which inhibits the proteolytic activity in autophagic bodies, did allow for the detection of vesiclelike structures in the vacuole, following a self-incompatible pollination. It has been previously shown that when a constitutive autophagy process is blocked in Arabidopsis root tip cells by E-64 treatment, there is an accumulation of undegraded cytoplasmic material in the central vacuole. Since unpollinated stigmatic papillae pre-treated with E-64 did not show the same accumulation of cytoplasmic material and vesicle-like structures in the vacuole, autophagy appeared to be induced in A. lyrata stigmatic papillae following self-incompatible pollinations. This was verified using two different autophagosome markers, MDC and GFPATG8a. As with other eukaryotic cells, autophagy is one of the major pathways for degradation of intracellular macromolecules in plant cells Autophagy can be induced with environmental stress conditions or during certain stages of development, and upon induction, targeted cytoplasmic components are enclosed by membrane sacs to produce a double-membrane bound autophagosome. The autophagosomes are transported into the vacuole to degrade the sequestered materials. The induction of autophagy following a self-incompatible pollination would help in pollen rejection by clearing vesicles/MVBs from the cytoplasm. It may also help to explain why we previously
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