Plant WEE1 Kinase Interacts with a 14-3-3 Protein, GF14ω but a Mutation of WEE1 at S485 Alters Their Spatial Interaction

ABSTRACT

In animals, 14-3-3 proteins bind two cell cycle proteins WEE1 and CDC25 stabilising their phosphorylated state. We report here for the first time interactions between WEE1 and 14-3-3 proteins both in vitro and in vivo in plants. The Arabidopsis 14-3-3 family partitions into either an Epsilon or Non-Epsilon group. In a yeast 2-hybrid screen Arabidopsis WEE1 interacted with the Non-Epsilon group. Subsequently, we focussed on Non-Epsilon GF14ω, a 14-3-3 expressed more strongly in proliferative than in non-proliferative cells and which is able to rescue a cell cycle checkpoint mutant in yeast. The WEE1/GF14ω interaction was confirmed by an in vitro co-immunoprecipitation assay and in vivo in tobacco BY-2 cells by bi-molecular fluorescence complementation. Sub-cellular interaction between WEE1 and GF14ω occurs in the nucleus of interphase cells. Additionally an interaction was very occasionally observed in the cross wall between cells. Their small stature and independent observations of callose, of the type that typically forms in new cell plates, suggests that this additional interaction might be occurring at cytokinesis. An S485A mutation of WEE1 abolished this interaction in vitro and altered the spatial interaction in vivo indicating that this is a likely regulatory phosphorylation target for the WEE1/GF14ω interaction.