| The plant cell wall is a strong fibrillar network that provides mechanical support to the cells, the tissues and the entire plant body. The mechanical strength of the plant body, which reflects the physical properties of cell walls, is an important trait for the adaptation of crops to different cultivation environments. The height of plant is important to improve productivity of rice. To investigate the complicated mechanisms of plant cell wall biosynthesis and mechanical strength of the plant in determine of plant height, we isolated the rice dwarf and brittle cu1m1 (dwb1) mutant, a pleiotropic phenotype controlling by a recessive mutant, from a japonica cultivar C418 produced by transgene approach. Allelism tests showed that the dwbl is not allelic to all of previously reported brittle culm mutants, from bc1 to bc3, indicating that it is a new gene determining culm strength and height. In dwbl, the content of cellulose is slight low than wild type, it showed that the phenotype of brittle culm is due to reducing of cellulose content. The dwbl mutant is classified as a dn-type, one of four kind of dwarf, which is the first report about fine-mapping of this kind of dwarf type. Physiological analysis showed that dwbl is insensitive to exogenous GA, indicating that it is controlled by GA signal. However, previous reports about the mutants presenting dwarf and brittle culm phenotype in rice are correlative with ethylene signal. Then, the relationship of GA signal with cellulose synthesis needs to be clear further. To determine the molecular basis of these defects, we tried to isolate the DWB1 geneby a map-based cloning approach. The fine mapping using 2,056 segregants enabled us to construct a BAG contig that encompasses the DWB1 locus, and finally defined it in a 143kb genomic region, which provided an important basis to finally clone it. The mechanism of brittle culm and dwarf phenotype would be elucidated by cloning of DWB1...
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