Abstract: 【Objective】 Three long empty glumes mutants were screened from a maintainer line Yixiang 1B(Oryza sativa L. ssp. indica) by ethyl methanesulfonate (EMS) mutagensis. This study is to explore the genetic basis and molecular mechanism for controlling the development of long empty glumes by gene mapping and cloning. And the temporal and spatial expression of related genes were also concerned. 【Method】 Three long empty glumes mutants, Oslg-1, Oslg-2 and Oslg-3, were analyzed by phenotypic observation, allelism identification, gene mapping, bioinformatics analysis, and expression analysis by quantitative PCR. 【Result】The glumes showed no obvious difference at the stage of early floret differentiation between wild type and mutant. However, the epidermal cells of glume presented significant difference during floret maturation. At the heading date, epidermal cells of abaxial glume presented bulge and rough nodules, and formed axially alignment. The epidermal hairs became more, and bulges arranged at a regular intervals, which were similar to the structure of epidermal cells of lemma. Genetic analysis suggested that the mutant Oslg-1 was controlled by one recessive nuclear gene. The Oslg-1gene was mapped between SSR markers RM5344 and RM20934, on the short arm of rice chromosome 7, with genetic distances of 1.11 cM and 0.82 cM, respectively, and with a physical interval of 246.3 kb. By analyzing and sequencing for the candidate genes in this genomic region, it was found that there was a single nucleotide change at 182 base (T→A) in exon of LOC_Os07g04670 gene, which caused a missense mutation at 61 amino acid (Leu to His) in the encoded product. Allelism analysis by inter-crosses showed that Oslg-1, Oslg-2 and Oslg-3 were allelic variation. Detection of the gene OsLG in Oslg-2 and Oslg-3 mutants was made and found that there was a single nucleotide change (316, T→A and 119, T→C) in exon of OsLG gene, which caused a missense mutation (106, Trp to Arg and 40, Leu to Pro) in the encoded product, respectively. These results suggested that the candidate gene may regulate the elongation of rice glume by the homologous gene sequence alignment and phylogenetic analysis. Besides, the relative expression content involved in OsLG gene and another PAP2 genecontrolling glume trait was also analyzed by real-time PCR (qRT-PCR). The results showed that OsLG gene was expressed in roots, leaf sheath and panicle, and presented rather higher expression in panicle than that in root and leaf sheath. By contrast, PAP2 gene was only detected in panicle. Therefore, both of OsLG and PAP2 were tissue-specificaly expressed, and PAP2 was much more higher expressed in panicle than OsLG. It was deduced that these two genes functioned in a synergistic pattern to control the development of long empty glumes as the expression level of OsLG and PAP2 were down in OsLG mutants. 【Conclusion】The Oslgmutants are allelic with G1 reported previously, and the mutation of a single amino acid in functional domain leads to the development of long sterile glume. OsLG and PAP2 are synergistically expressed in panicle.

Key words: rice, long empty glumes, allelic variation, gene cloning, gene expression