“…After binding, SRK activates a signaling pathway in the stigmatic papilla that rapidly rejects pollen by blocking pollen hydration or pollen tube penetration into the stigmatic surface (reviewed in Chapman and Goring, 2010;Ivanov et al, 2010). The SCR/SP11 and SRK genes are highly polymorphic, and alleles have been identified in other species, including A. lyrata (Kusaba et al, 2001;Schierup et al, 2001Schierup et al, , 2006Prigoda et al, 2005;Mable and Adam, 2007) and C. grandiflora (Paetsch et al, 2006;Boggs et al, 2009b;Guo et al, 2009). Downstream of SRK in the self-incompatibility pathway, there are two positive regulators that have been shown to interact with SRK, M locus Protein Kinase (MLPK) and the E3 ubiquitin ligase, ARM-Repeat Containing1 (ARC1) (Gu et al, 1998;Kakita et al, 2007aKakita et al, , 2007b.…”