PEK14: A Kinesin-4 Necessary for Male-Derived Fertility in Arabidopsis thaliana.

Of the 61 kinesins annotated in Arabidopsis thaliana , many are still without assigned function. Here, we have screened an insertional mutant library of Arabidopsis pollen-expressed kinesins for fertility defects. Insertional mutants for three kinesins showed a significant reduction in seed set. Among them, we focused on the sole kinesin-4 expressed in pollen (kinesin-4C, here Pollen-Expressed Kinesin 14, PEK14). We show a seed-set defect in the three independent alleles pek14-1, pek14-2, and pek14-3. This defect is male-derived and is equally distributed throughout the silique. Mature pek14-1 anthers contain about 10% inviable pollen grains. pek14-1 pollen tubes grow 20% more slowly and show reduced pollen tube bending. Analysis of the male germ unit (MGU), as it travels through the pollen tube, demonstrates an aberrant organization of the pek14-1 MGU in 30% of pollen tubes and an increase in the distance of the MGU to the tip by 24%. Expression of GFP-tagged PEK14 successfully complemented the observed seed set defect, as well as the growth rate, bending, and MGU organization defects observed in pek14-1. In pollen, PEK14-GFP is located diffusely at the pollen tube tip. PEK14-GFP is also expressed in the root meristematic zone and is located at the mid-zone of the phragmoplast, but no apparent root growth phenotype was observed, likely due to redundancy in this organ.