Floral Organ Structural Characterization,genetic Analysis And Molecular Tagging Of Genes For Two Mutants From Rice

Rice (Oryza sativa L.) is not only one of the most important food crops in the world, but also a model plant for study of the molecular developmental biology in monocots. Although over 20 MADS-box genes were isolated from rice by using the conserved sequences of the MADS-box genes of dicots as probe screening the rice genomic library or eDNA, it is very difficult to determine the functions of these rice MADS-box genes without classical mutants. Furthermore, the study of the function and expression of genes using mutants is a trend in functional genomxcs. Rice flowers, like their eudicot relatives, have stamens and carpels but lack obvious sepals and petals. Instead, rice-specific organs known as the lemma, palea, and lodicules surround the stamens and carpels of rice flowers. Although some have considered the lodicule to be equivalent to a dicot petal, the evolutionary relationship between palea / lemma and dicot sepals have also been variously interpreted and widely debated. We discovered two mutants from indica rice line SARIII-93-369 and W-255, respectively. One of the two mutants without palea(rice non-palea mutant), another show homeotic conversion of pistil into stamens and the loss of midrib(dl(t) mutant) in this study, we have completed the investigation of the anatomical structure of floral organs ,genetic analysis of mutant traits and molecular tagging of genes of two mutants. The main results ar summarized as follows. 1. About the rice non-palea mutant (1) The investigation of the floral anatomical structure: Comparison the structure of rice non-palea mutant floral organs with of nomial iice floral organs shows that 3 mutant flowers have normal glumes, lemma, lodicules, stamens and carpels, but they lacked palea and generated two additional glume-like organs. According to these results, we presented the following several corollaries: ?Lemma and palea are different organs in rice; alea maybe is equivalent to a dicot sepal;c~)the gene of non-palea mutant belongs probably to A function gene. (2) Genetic analysis of non-palea mutant: Three P2 populations, Sheng47/ mutant, N625/ mutant and CDR22/ mutant were developed, the result of genetic analysis indicated that the traits of non-palea mutant is controlled by a single recessive gene. (3) Molecular tagging of gene of non-palea mutant: The F2 population, derived from mutant! Sheng47, was used to screen molecular markers linked with non-palea gene. Subsequently, the gene was mapped between two restriction fragment length polymorphism markers, RZ450 and C498 on chromosome 6,with distances of 2.4 and 7.5 cM, respectively. This gene is temporarily designated as npa-1. 2. About the dl(t) mutant (1) Plant phenotype and floral anatomical structure of dI(t) mutant: The dlQ) and other four dl mutations, dl-], dl-2. dl-supl and dl-sup2 (Nagasawa et al, 1996), exhibited drooping leaves without midrib and abnormal pistils with variable degrees depending on the alleles. By comparison with other four mutations, dl(t) mutant exhibited typically open hull, stamens with thinner and longer filament, the pistil transformed completely to stamens accounting for about 2% of flowers, about 98% of flowers produced staminoid pistil in addition to the same mutant phenotype drooping leaves lacking midrib. According to the...