Arabidopsis Fused kinase TWO-IN-ONE dominantly inhibits male meiotic cytokinesis
Arabidopsis Fused kinase TWO-IN-ONE (TIO) controls phragmoplast expansion through its interaction with the Kinesin-12 subfamily proteins that anchor the plus ends of interdigitating microtubules 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. To characterize TIO functions further, we expressed TIO and a range of TIO variants under control of the TIO 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 show sporophytic abnormalities indicative of polyploidy. These phenotypes arose independently in TIO variants in which either gametophytic function or the ability of TIO to interact with Kinesin-12 subfamily proteins was abolished. Interaction assays in yeast showed TIO to bind to the AtNACK2/TETRASPORE, and plants doubly homozygous for kinesin-12a and kinesin-12b knockout mutations to produce enlarged pollen grains. Our results show TIO to dominantly inhibit male meiotic cytokinesis in a dosage-dependent manner that may involve direct binding to a component of the canonical NACK-PQR cytokinesis signaling pathway.
KeywordsTWO-IN-ONE Fused kinase Dominant inhibition Cytokinesis Meiocytes Arabidopsis
We thank Prof. Bo Liu (University of California, Davis, USA) for the original kinesin-12a; kinesin-12b doubly homozygous mutant seeds and Prof. Hong Gil Nam (DGIST, Republic of Korea) for a vector containing two copies of HA tag. We thank the ABRC for providing seeds of SALK lines (SALK_046315 and SALK_027920) for the Kinesin-12 subfamily genes and tes-4 mutant allele (CS9353). We also thank Anchillie Franchesco for assistance with plant growth and maintenance. This research was supported by the Basic Science Research Program, National Research Foundation of Korea (Grant 2011-0011141) and the Next-Generation BioGreen21 Program, Rural Development Administration, Republic of Korea (Plant Molecular Breeding Center No. PJ008137), to SKP and by the UK Biotechnology and Biological Sciences Research Council to DT.
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