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Arabidopsis fused kinase TWO-IN-ONE dominently inhibits male meiotic cytokinesis
Arabidopsis Fused kinase TWO-IN-ONE (TIO) controls phragmoplast expansion and interacts with the Kinesin-12 subfamily proteins that anchor the plus ends of interdigitating microtubules (MTs) in the phragmoplast midzone. Previous analyses of loss-of-function mutants and RNA interference lines revealed that TIO positively controls both somatic and gametophytic cell cytokinesis, however, knowledge of the full spectrum of TIO functions during plant development remains incomplete. In order to further characterize TIO functions, we expressed TIO and a range of TIO variants under control of its own promoter in wild type Arabidopsis plants. We discovered that TIO-overexpressing transgenic lines produce enlarged pollen grains, arising from incomplete cytokinesis during male meiosis, and showed sporophytic abnormalities indicating polyploidy. These phenotypes arose independently in TIO variants that abolished either gametophytic function or the ability of TIO to interact with Kinesin-12 subfamily proteins. Interaction assays in yeast showed TIO to bind to AtNACK2/TETRASPORE and plants doubly homozygous for kinesin-12a and kinesin-12b knockout mutations to produce enlarged pollen grains. Our results show that TIO dominantly inhibits male meiotic cytokinesis in a dosage dependent manner that may involve direct binding to acomponent of the canonical NACK-PQR cytokinesis signaling pathway.
