Morphogenesis and Molecular Basis on the Unclosed Glumes, a Novel Mutation Related to the Floral Organ of Rice

The development of the rice floral organ directly affects rice yield and quality, and rice spikelet development has always been the hotspot in the field of botanical research. Mutants of the rice floral organ are very important intermediate materials which are used to reveal the genetic mechanism of spikelet development. In the present study, a stable rice mutant named unclosed glumes ( ucgl ) with a Japonica background, of which the lemma and palea cannot close fully after flowering, was isolated from the population mutagenized by using the ethyl methane sulfonate (EMS) in rice. Results from the genetic analysis indicated that the mutant was controlled by a single recessive gene. The UCGL locus was mapped to a 118-kb region between SSR makers R8UM89 and RM23258 on chromosome 8. There was a C to T substitution at the fifth exon of LOC _ Os08g0459600 by sequencing analysis. LOC _ Os08g0459600 encodes 12-oxo-phytodienoic acid reductase 7 ( OPR7 ), which is one of the key enzymes in the jasmonic acid (JA) biosynthesis. RT-PCR analysis showed that the UCGL gene could be expressed in all of the tested tissues including roots, stems, leaves, and panicles. Also, the concentration of endogenous JA in the ucgl mutant was reduced in contrast to the wild-type. The expression levels of JA biosynthetic genes including OsLOX and OsAOS were significantly increased in the ucgl mutant plant. The expression of UCGL ( OsOPR7 ) could regulate JA metabolism and affect the closure of glumes in rice. As far as we know, the UCGL is thus a new gene and has not been reported as controlling the closure of rice glumes, thusthe study of it could provide a new insight into the role of JA in rice floral morphological development.