Screening Novel Mutants In Arabidopsis With Altered Response To Cytokinin

This work is based on the mutant ckrcl-1 (cytokinin induced root curlingl-1) isolated previously by our research group. CKRC1 encodes tryptophan aminetransferase in Arabidopsis (TAA), catalyzing the formation of IPA from tryptophan through its oxidative aminetransferring activity, the first step of the IPA pathway for IAA biosynthesis. ckrcl-1 has typical low auxin phenotypes, and displays curling roots when placed on the cytokinin-containing medium. Considering multiple pathways of IAA synthesis and their complex molecular regulation, it should be feasible to get more novel non-allelic mutants having the same phenotype as ckrcl, Molecular genetic and biochemical studies on these mutants would provide new insight into the complicated biology of auxin in plant growth and development.By screening-120,000 seedlings in about 40,000 T-DNA inserted lines.,we isolated 5 root curling mutants, which can be classified into 2 groups:root curling (rcl, curling without exogenous cytokinin) and cytokinin induced root curling (ckrc). The former includes 023(rcll-1).024(rcl2-1 and 069(rclS-1 and the latter includes 052(ckrc2-1)和066(ckrc3-1). Sequence analysis of the Tail-PCR products showed that the T-DNA inserted sites of mutant 023 (rcll-1),052 (ckrc2-1) and 069 (rcl3-1) are the 3'-UTR (untranslated regions) of AT2g39990 [encodes eukaryotic translation initiation factor 2(EIF2)], the 6th intron of AT2g38120 (AUX1) and the 10th intron of AT1g01650 (encodes peptidase), respectively.Chemical complementation with different auxins and IPA to the 5 mutants showed that the phenotypes of some mutants can be rescued to various extents by these chemicals. Genetic analysis indicated that 023 (rcll-1),024 (rcl2-1),052 (ckrc2-1) and 066 (ckrc3-1) are all recessive mutations.