Cloning And Functional Analysis Of Rice Lateral Root Development Related Gene OsSLR1

Using EMS-generated rice mutant library,we found three rice short root mutants,named as Osslr1-1,Osslr1-2 and Osslr1-3,respectively.The root elongation(including lateral root,primary and adventitious roots) of the mutant is retarded.Map-based cloning indicates that the mutant phenotype is controlled by a single recessive gene.The research on the mutant indicates the following results:1.Osslr1 mainly affect root elongation including primary roots,adventitous roots and lateral roots.The mutant also showed reduced shoot gravitropism and maximum tiller numbers.2.Genetic analysis indicated that the mutation was controlled by a single recessive gene.By map-based cloning using F₂ mutants,OsSLR1 was mapped on BAC P0506A10 in Chr1.Sequencing analysis revealed that a point-mutation was occurred at 5153bp of the gene.The mutation results in a exchange of C to T,and consequently change of Glutamine to termination codon.Bioinformatics analysis indicated that OsSLR1 encodes a novel protein with unkown function.Complemetation and allelism tests comfirmed that the Osslr1 mutant phenotype is caused by loss of OsSLR1 function.3.RT-PCR and OsSLR1 Promoter:GUS analysis indicated that OsSLR1 expresses in whole plant tissues including roots,base of root-stem,stem,leaves and flowers.OsSLR1 protein is predicted to have a mitochondrion-targeting peptide, and this prediction was confirmed by subcellular localization of OsSLR1-GFP fusion protein.4.Osslr1 mutant showed defect in uptake of Mn²⁺,Fe²⁺,Zn²⁺,Mg²⁺,Ca²⁺ ect. especially Mn²⁺,its content in shoot of the mutant was only about one tenth of that of WT.The root elongation of slr1 showed hypersitive to high manganese, whereas upper part of slr1 showed increased tolerance to high manganese, indicating the very importance role of OsSLR1 for assimilation of Manganese in rice.Iron content in shoot of the mutant declined about 60%compared with WT.RT-PCR results showed a number of genes involved in various steps of Fe(â…¡) and Fe(â…¢) uptake and transport were up-regulated in the slr1 mutant seedlings under Fe(â…¡) or Fe(â…¢) supply conditions,consistent with the declined of iron content in the mutant.Osslr1 mutant also showed hypersensitive to calcium-deficiency and low nitrogen stress in term of root elongation.Taken together,OsSLR1 play an important role in rice root growth and development and divalent cation assimilation or transport.