ARABIDOPSIS CYCLIN-DEPENDENT KINASE GENE CDKG;2 IS INVOLVED IN ORGANOGENIC RESPONSES INDUCED IN VITRO

The Arabidopsis CDKG;2 gene encodes a putative cyclin-dependent Ser/Thr protein kinase of unknown biological function. This gene shows structural similarity to animal and human cyclin-dependent (PITSLRE) kinases. This study used the homozygous knockout cdkg;2 mutant based on T-DNA insertional line SALK_090262 to study the effect of mutation of the CDKG; 2 gene on explant response and in vitro plant regeneration. For callus induction and proliferation, hypocotyls and cotyledons of 3-day-old seedlings of cdkg; 2 and A. thaliana ecotype Col-0 were cultured on solid MS medium supplemented with 2,4-D (2 mg l(-1)). Organogenesis was induced after callus transfer on MS + TDZ (0.5 mg l(-1)). The initiation time of callus and shoot induction differed between the mutant and control cultures. Shoot regeneration after callus transfer on MS + TDZ was delayed in cdkg; 2 (31 days versus 7 days in Col-0). Shoots formed on callus derived from Col-0 hypocotyls but not on cotyledon-derived callus; in cdkg; 2, shoots developed on both callus types. Mutant shoots did not form roots, regenerants were dwarfed, and inflorescences had small bud-like flowers with a reduced corolla and generative organs. Abnormalities observed during cdkg; 2 organogenesis suggest a role of CDKG;2 as a regulator of adventitious root initiation.