Abstract
A loss-of-function mutation in CDKA;1, encoding the only Arabidopsis CDKA, results in male gametophyte lethality, because the second division of the generative cell, pollen mitosis II (PMII), is disrupted in this cdka-1 mutant. Although almost all mature pollen grains of wild type Arabidopsis were tricellular, those of heterozygous cdka-1/CDKA plants contained bicellular and tricellular at about a 1:1 ratio. About 25% tricellular pollen grains were recovered when the wild type CDKA;1-GFP was heterozygously introduced into cdka-1/CDKA plants, implying that the CDKA;1-GFP was functional in the PMII cell division. In this study, the CDKA;1 mutants were introduced into cdka-1/CDKA plants. As with the result of wild type CDKA;1-GFP, introduction of CDKA;1(T161E)-GFP, which can mimic phosphorylated T161, resulted in successful complementation in the cdka-1 mutant. However, introduction of CDKA;1(T161A)-GFP did not complement the cdka-1 mutant, indicating that phosphorylation of T161 in Arabidopsis CDKA;1 is required for the PMII cell division.
