A novel F-box protein represses endothecial secondary wall thickening for anther dehiscence in Arabidopsis thaliana

In plants, the regulation of protein turnover by the ubiquitin proteasome system (UPS) is a key posttranslational mechanism underlying diverse cellular processes. However, the participation of the UPS in cellular processes involved in anther dehiscence, especially endothecial secondary wall (ESW) thickening, has not been characterized. Here, we report that a novel F-box protein in arabidopsis, designated SAF1 (Secondary wall thickening-Associated F-box 1), negatively regulates ESW thickening in the anther. SAF1 is predominantly expressed in flower tissues and interacts with Arabidopsis-Skp1-like 19 (ASK19). SAF1-overexpressed (Ox) lines showed reduced fertility due to a lack or loss of ESW thickening in the anther and inhibition of the expression of relevant genes, such as IRREGURAR XYLEMs (IRXs) in flowers. These findings suggest that the novel Skp/Cul/F-box (SCF) complex consisting of SAF1 as an F-box protein and ASK19 as a Skp functions in secondary wall thickening of the anther endothecium.