| Rice (Oryza sativa L.) is one of the model plant in monocotyledons, and also be one of the mostimportant cereal crops in the world. The floral organ identity have an important effect on traits such asyield and quality of rice. So it is helpful for us to understand the progress of floral organ developmentand promote the learning of molecular breeding via identifying more and more floral organ mutants andfunctional analysis. In this study, we characterized a rice floral organ mutant, bhl (beak-like hull1) witha beak-shaped hull, were obtained from a T-DNA library generated from the rice cultivar Asominoir. AF2segregation population cross between bhl and Nanjing11were used for fine-mapping and candidategene predicting analysis of the mutant gene bhl. Moreover, histology analysis were also well studied inbhl. These results preliminary revealed that the genetic mechanism of lemma and palea, which lead agood foundation for elaborating the molecular mechanism of BHL Results from our experiment aresummarized as follows:1)the lemma and palea of bhl exhibited a slender and longer phenotype and developed toward tothe palea side, which showed a beak-shaped hull. The inner floral organs, such as lodicules, stamens andpistils, and surrounding structures such as rudimentary glumes and sterile lemmas are all normal as wildtype. Moreover, bhl mutation have a significant impact on thousand grain weight, seed set rate, grainlength, grain width, hull thickness and germination rate etc. Inspection of transverse sections of the bhland wild type hulls showed a notable expansion in the number of fibrous sclerenchyma cells in bhl, butthe other three cell types (silicified cell, spongy parenchymatous cell and non-silicified cell) werenormal in bhl. The increase of fibrous sclerenchyma cells which will increase the hull thickness, and itfinally result in reducing the seed set rate of bhl. Scanning electron microscope analysis showed thatlemma and palea primordia initiation and the other floral organs development were normal in bhl, butthe lemma and palea started to develop curve and slender toward to the palea side on the late stage (Sp7)in bhl floral development.2)Real-time PCR analysis revealed that the genes OsMADSl, OsMADS14, OsMADS15,OsMADS18, REP1, CFOl and DL, all of which are also involved in lemma and palea development andidentity specification, were down-regulated in the bhl mutant. These results indicated that BH1maybe aupstream gene among these relative genes, and is therefore an important floral organ development gene.3)Genetic analysis revealed that the bhl mutant phenotype was determined by a single recessivegene. Through mapping the F2population produced by bhl crossing Nanjingll, the bhl locus wasmapped within a region of about87.5kb on the long arm of chromosome2. An analysis of the genecontent of this region indicated that the mutation involves the loss of a55kbp stretch. Through RiceAnnotation Project Database system, Nine putative genes were included in the region of87.5kb, andthere were four open reading frames deleted in bhl. RT-PCR analysis revealed that only the secondORF (LOC0s02g56610) was expressed in young spikelet of wild type among these four predictedgenes, which was subsequently designated as BHL... |
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