Gene Positional Cloning And Functional Analysis Of A Developmentally Retarded Mutant (drml) In Arabidopsis

A developmentally retarded mutant(drm1) was obtained in Arabidopsis from ethyl methanesulfonate(EMS)-mutagenized M2 seeds in Columbia(Col-0) genetic background.Its lifespan was extended to 150-180 days.Genetic analysis indicated that the mutant phenotype was caused by a single nuclear recessive mutation.We created a F2 mapping population consisted of more than 3100 individuals.The mutation site was positioned within AT5G64960(CDKC;2) on the bottom of chromosome 5 by map-based cloning and sequencing.A "g" to "a" change was detected at the position 550 of the full length cDNA (1542bp) of CDKC;2 in drm1,which caused a amino acid change from "G" to "R" at position 184.Complementation result confirmed that the missense mutation of CDKC;2(DRM1) caused the mutant phenotype of drm1.Overexpression of CDKC;2 in Col-0 caused the plant to bolt approximately five days earlier than the wild-type.An expression pattern analysis revealed that the gene expressed almost across the whole lifespan. ELISA analysis demonstrated that the endogenous ABA level in drm1 was increased significantly/dramatically by 32.7%,383.3%and 61.1%at vegetative phase,transition phase and flowering phase respectively.The mutation also disturbed the capabilities/potentials of drought tolerance, disease resistance and photomorphogenesis,but the underlying mechanism is largely unknown.No CDKC;2 mutants have so far been reported.Our work has for the first time revealed a general role of CDKC;2 in plant growth and development.Possible involvements of CDKC;2 in regulating ABA metabolism and cell cycle are discussed.