Cloning And Functional Analysis Of OsAIM1 In Root Development In Rice(Oryza Sativa)

Root is vital to acquire water and minerals from the soil. The root elongation is determined by mitotic activity and cell elongation ability in the root apex. Up to now, a number of genes have been reported to participate in root cell elongation therefore affect root elongation in rice. However, few were discovered to regulate mitotic activity of rice root apex. To identify new genes involved in regulating root mitotic activity in rice, we screened a Co60-mutagenized rice mutant library, and isolated a short root mutant, Osaim1, the root cell elongation of which is normal.The primary and crown root length of mutant is around half of that in wild type, while the crown root number and lateral root development are normal. The short root mutant shows a reduction in root meristem size. However, mature cell length, root cap, and the root radical pattern organization of the mutant seems normal.To dissert the root mitotic activity of the mutant, an Edu labeling and CYCB1;1::GUS assays were used to visualize the cells in S phase and G2-M transitions of the root apex. It showed that Osaim1 has a reduced mitotic activity in the primary root apex.The map-based cloning results showed that the mutant was due to a deletion of 26 bp in OsAIM1 （LOC₀2g17390） lacated on short arm of chromosome 2, which encodes a multifunctional protein that function in peroxisomalβ-oxidation.The introduction of OsAIM1 genomic fragment into the mutant fully complemented the mutant’s defect, which indicates that Osaim1 is responsible for the mutant phenotype.Based on the GUS staining pattern of OsAIM1 promoter::GUS fusion reporter, OsAIM1is expressed on various organs, including root tip, lateral root, root hair, leaf, and flower.How the OsAIM1 participates in regulating the mitotic activity of the rice primary and crown root still need to be addressed.