Isolation And Characterization Of Auxin Mutants In Arabidopsis Thaliana

Auxin is the main plant hormone which regulates various aspects in plant growth and development.Although auxin was discovered more than seventy years ago,research on auxin biosynthesis has been proved to be difficult and challenging.So far,only one complete pathway of de novo auxin biosynthesis in plants has been firmly established.A Tryptophan-dependent auxin biosynthesis pathway is known as the IPA pathway.The paper is about isolating auxin-deficient mutants which obtained by our forword genetic screen.We hope we can get novel auxin-deficient mutants and complete the auxin biosynthesis pathway.Our research group had been established a forword genetic screen for isolating auxin-deficient mutants.Cytokinin can induce strong root curling named ckrc(Cytokinin induced root curling),a phenotype easily to be used as a ’marker’ for isolating more auxin-deficient mutants.The ckrcl/taal mutant was isolated from this screen.The characteristics of ckrcl suggest the action mechanish between cytokinin and auxin in root to some extent.CKRC1/TAA1 encodes a previously identified tryptophan aminotransferase(TAA1)involved in the indole-3-pyruvic acid(IPA)pathway and catalyse the biosynthesis of indole-3-acetic acid(IAA).Recently study show that YUCs play an important role in converting IPA to IAA.The YUCs and TAAs participate in the same auxin biosynthesis pathway and YUCs work downstream of TAAs.Based on this screen,we eventually isolated 53 ckrc-like mutants from several T-DNA insertion lines.And give a priority study to c5 and lb113.We classify the 53 mutants as four groups according biochemical complementation.12 mutants belong to auxl group,26 mutants belong to eirl/pin2 group,5 mutants belong to ckrcl group and 2 mutants belong to ckrw(Cytokinin induced root waving)group.Further genetic allelic test imply c6,c8,lc6 and lc15 are the allelic of eirl/pin2,le85 and le4 is the allelic of ckrcl and lb72 is the allelic of yuc8.The filament of c5 is short and there are also aborted pollen grains of c5.These are the reasons for the low ripening rate.The primary root and hypocotyl are shorter than WT plants in lb113 mutant.lb113 mutants are dwarf plant with short petioles,small seeds and highly shoot branching.According to the phenotype of lb113,we consider that lb113 resemble to auxin-deficient mutant.Genetic hybridization suggests that c5 and lb113 are recesive mutants.The identification of the mutant genes and Quantification of IAA content are under way.