Identification of a Novel SBP1-Containing SCF Complex in Wild Dwarf Almond ().

S-RNase-based gametophytic self-incompatibility (SI), in which specificities of pistil and pollen are determined by S-RNase and the S locus F-box protein, respectively, has been discovered in the Solanaceae, Plantaginaceae, and Rosaceae families, but some underlying molecular mechanisms remain elusive and controversial. Previous studies discovered SI in wild dwarf almond (), and pistil S (S-RNase) and pollen S (SFB) determinant genes have been investigated. However, the SCF (SKP1-Cullin1-F-box-Rbx1) complex, which serves as an E3 ubiquitin ligase on non-self S-RNase, has not been investigated. In the current study, (), (), , and genes (S-haplotype-specific F-box) were identified in an accession (ZB1) of . Yeast two-hybrid assays revealed interactions between and and between and s ( and ), and subsequent pull-down assays confirmed these interactions, suggesting a novel SBP1-containing SCF complex in wild dwarf almond. Moreover, despite a putative interaction between and , we revealed that does not interact with or , and thus the canonical SSK1-containing SCF complex could not be identified. This suggests a novel molecular mechanism of gametophytic SI in species.