Identification And Cloning Of Functional Genes Of Three Rice Architecture Determinant Mutants

In this study,three mutants with altered plant architecture were derived from irradiation and designated rad-1,rad-2 and rad-3,respectively.We compared their phenotype and agronomic traits,also constructed segregation population for further gene mapping and cloning.The main results were shown as follows:1)Based on the morphological observation and agronomic traits investigation,we found that three mutants all exhibited bent seedling growth,wrinkled leaves,stunt growth,reduced number of primary branches,secondary branches,seed rate,grain number per panicle and grain weight.Compared with the wild type,rad-1 and rad-2 becomes shorter than the wild type,and rad-3 increased in grain length significantly,as well as shortened in grain width.2)Through cytological observation,uneven size of stem epidermal cells and irregular arrangement were observed in each mutant,which maybe the cause of distortion in seedlings.Paraffin sections showed shorter cells in the first internodes in mutants,indicating a plausible reason for plant dwarfing.The length of inner cells of lemma in rad-1 and rad-2 were shortened but the number was not changed;whereas,reduced length and increased number of cells were detected in rad-3.3)Genetic linkage analysis and allelic test confirmed that rad-1 and rad-2 are allelic to each other.The candidate gene of these two mutants were defined on chromosome 7,flanked by markers NJ7-29 and NJ7-18,a region with 230kb;and the candidate gene in rad-3 were located on chromosome 3,restricted by marker RM14898 and Q4646-20,a region with 2.64Mb.4)One gene,encoding rice type ? formin-like protein OsFH5 were located in the candidate gene region of rad-1 and rad-2,thus sequence analysis were conducted.An 8-bp deletion in exon 2 in rad-1 and a single nucleotide change in intron 14 in rad-2 made frame-shift reading and produced truncated proteins.OsFH5 gene exhibits constitute expression in tested tissues,especially abundant in the seedlings.Compared with the wild type,prominent decline of OsFH5 gene were observed in each mutant.5)One gene,encoding villin protein present in the candidate region of rad-3,which also showed constitutive expression pattern.Quantitative analysis revealed that this gene was down-regulated significantly in the mutant.Sequence analysis found that two kind of transcripts were present both in wild-type and the mutant.Whether two transcripts or genomic sequences(including 5kb in promoter and the 11.55kb coding region),no variation were discovered,suggesting a regulator of this gene may mutant or post-translation regulation was occurred.6)Compared with the wild type,more or less sensitivity to IAA gradient was found in the mutans.The down-regulated expression levels of several ARF auxin response factor were detected,which suggested that OsFH5 likely to affect the response to auxin.