Mapping And Cloning Of Two Arabidopsis Mutants Hypersensitive To Light

To study the mechanism by which plants respond to light,we identified two Arabidopsis thaliana T-DNA mutants,62 and 113.Mutant 62 had significantly short hypotocyls and was hypersensitive to red light,whereas mutant 113 had short hypocotyls under both red and far red light.The function of the two mutated light signaling components in Arabidopsis seedling photomorphogenesis was explored phenotypically and molecularly.We first analyzed various phenotypes of the two mutants under predetermined optimal light densities.In addition to its short hypocotyl under red light,mutant 62 also accumulared significantly more chlorophyll and anthocyanin pigments.In contrast,mutant 113 accumulated much less chlorophyll and anthocyanin pigments.At the same time,qRT-PCR shows that.The expression level of CAB3 and CHS genes was significantly increased in mutant 62,but reduced in mutant 113 compared to that of the Col-0 wild type.Further genetic analysis showed that the 62 mutation was semi-dominant,whereas the 113 mutation was recessive.Through combined approaches of rough mapping and high-throughput sequencing,we identified a T-DNA insertion in the promoter of PHYB in mutant 62 chromosome 2.Mutant 113 had a T-DNA inserted in the gene At4g36380 on Arabidopsis chromosome 4.Through qRT-PCR analysis,PHYB was found overexpressed in mutant 62,resulting the various photomorphogenic phenotypes such as short hypocotyls,reduced chlorophyll accumulation,and larger cotyledons.In mutant 113,a T-DNA was found inserted in gene At4g36380,causing the deletion of a small DNA fragment.Furhter allelic analysis of the mutant 113 and rot3 confirmed that the mutant phenotype of mutant 113 is due to a T-DNA insertion in the ROT3 gene.ROT3 is involved in BR biosynthesis,and may position at an intersection with light signaling.Future research will be directed towards the understanding of molecular mechanisms by which red and far red light signal transduction cross-talks with BR biosynthesis.