CDKG1 Is Required Pollen Wall Formation In Arabidopsis Thaliana

Cyclin-dependent protein kinases (CDKs) are a group of protein kinases which are originally characterized as being involved in cell cycle regulation in eukaryotes. However, there are also exceptions such as CDK9s and AtCDKC2, which do not regulate cell cycle. Here we report a CDK encoding gene, CDKG1, which is required for early pollen wall development but not cell cycle in Arabidopsis. The CDKG1 T-DNA insertion mutant exhibited a partial male sterile phenotype due to the abortion of postmeiotic microsporogenesis. Histological analysis showed that the primexine patterning and pollen wall formation is impaired in cdkg1, and tapetum secretory function is also affected. Aniline blue staining indicated that callose deposition of tetrads in cdkg1 is affected compared with that in wild type. Furthermore, the CalS5 gene, which was required for callose synthesis, was down-regulated in cdkg1. CDKG1 expressed extensively in all vegetative and reproductive organs, and in situ hybridization showed that CDKG1 expressed relatively strongly in the tapetum cells and microspore mother cells at tetrad stage. In conclusion our results suggest that CDKG1 is involved in pollen wall development but not cell cycle regulation.