The Arabidopsis SKP1-like genes present a spectrum of expression profiles.

The yeast Skp1 protein is a component of the SCF complex, an E3 enzyme involved in the specific protein degradation pathway via ubiquitination. Skp1 binds to F-box proteins to trigger specific recognition of proteins targeted for degradation. SKP1-like genes have been found in a variety of eukaryotes including yeast, man, Caenorhabditis elegans and Arabidopsis thaliana. The Arabidopsis genome contains 20 SKP1-like genes called ASK (for Arabidopsis SKP1-like), among which only ASK1 has been characterized in detail. The analysis of the expression pattern of the ASK genes in Arabidopsis should provide key information for the understanding of the biological role of this family in protein degradation and in different cellular mechanisms. In this paper, we describe the expression profiles of 19 ASK promoter-GUS fusions in stable transformants of Arabidopsis, with a special emphasis on floral organ development. Four ASK promoters did not show any detectable expression in either inflorescences or seedlings. Our results on the ASK1 expression profile are consistent with previous reports. Several ASK promoters show clear tissue-specific expression (for instance in the connective of anthers or in the embryo). We also found that almost half (9/19) of ASK promoters direct a post-meiotic expression in the male gametophyte. Tight regulation of the expression of this gene family indicates a crucial role of the ubiquitin degradation pathway during development, particularly during male gametophyte development.