In eukaryotes, the ubiquitin-mediated protein degradation pathway has been shown to control several key biological processes such as cell division, development, metabolism and immune response. F-box proteins, as a part of SCF (Skp1-Cullin (or Cdc53)-F-box) complex, functioned by interacting with substrate proteins, leading to their subsequent degradation by the 26S proteasome. To date, several F-box proteins identified in Arabidopsis and Antirrhinum have been shown to play important roles in auxin signal transduction, floral organ formation, flowering and leaf senescence. Arabidopsis genome sequence analysis revealed that it encodes over 1000 predicted F-box proteins accounting for about 5% of total predicted proteins. These results indicate that the ubiquitin-mediated protein degradation involving the F-box proteins is an important mechanism controlling plant gene expression. Here, we review the known F-box proteins and their functions in flowering plants.
Self_incompatibility (SI) is a major genetic mechanism to prevent self_fertilization in flowering plants and, in most cases, controlled by a single multiallelic locus, known as the S locus. In Brassica , the genes mediating both stylar ( SRK, S receptor kinase) and pollen (SCR/SP11, S locus cystein rich protein/ S locus protein 11) expression of self_incompatible reaction have been characterized though the first S locus_encoded gene, SLG (S locus glycoprotein), was isolated nearly fifteen years ago. These findings have finally unveiled the molecular partners in pollen recognition during self_incompatible reaction in Brassica .
