Figure 7.

Molecular model of the self‐incompatibility (SI) response in the Brassicaceae. The S‐locus consists of three genes, SRK, SP11 and SLG. The SRK receptor kinase (in blue) is the female factor and covers the plasma membrane of the stigma papilla cell. SP11 (in red) is the male component that is mainly expressed in the anther tapetum where it accumulates in the outer layer of the pollen cell wall during maturation. The pollen SP11/SCR ligand binds to stigma SRK, leading to auto‐phosphorylations of SRK as well as phosphorylation and activation of ARC1. ARC1 ubiquitinates EXO70A1 and GL01. The ubiquitination of EXO70A1 blocks further hydration of the incompatible pollen, whereas the proteasomal degradation of GLO1 is thought to lead to an increased level of the cytotoxic methylglyoxal (MG). Adapted from (Jany et al., 2019; Takayama and Isogai (2005)).