| Identification and clone of novel mutant genes of floral organ in rice would play an essential role in understanding the molecular genetic mechanisms and molecular signal pathways regulating floral organ development. In this paper, map-based cloning of GLL gene conferred glume-like lodicule (gll) floral spontaneously mutated in fields were conducted. Meanwhile, the agronomic traits, such as rice quality, physiological characteristics of photosynthesis were analyzed. Results are as follows:1. Field identification, comparison between mutant and wild-type floral organs, statistics of segregation of different phenotype as well as gene mapping based on map-based cloning were used to descript the characteristics of floral organ, to determinate the inheritance of gll mutant and high-resolution mapping of GLL gene. It was shown that a wide variety of spikelet developmental defects exhibit from outer to inner floral organs in gll mutant, which main mutant phenotypes are glume-like lodicule and the extra glume. The Chi-square test of F2 individuals derived from four crosses, indicated that the segregation ratio of phenotypes is consistent with inheritance of single recessive nuclear gene. The plants with gll phenotype were obtained from F2 and F3 generations from Nipponbarexgll for mapping GLL gene. One hundred and fifty-six polymorphic molecular markers, which evenly distributed on 12 chromosomes in rice, were used to test 880 individuals with mutant phenotype. According to statistical analysis, the GLL gene was located on rice chromosome 1 between RM7246 and RM12031 with a physical distance of 17 kb.2. Gene sequencing and related bioinformatics analysis, candidate gene was identified. GLL gene is a new allele of the EG1, which is caused by one point mutation happened in 541th base. Analysis of cis-elements found in GLL, it found that GLL is not only related to floral organ development, but also to the plant hormone signal transduction and stress response. Nine amino acid sequences in Arabidopsis and other species were found 38% to 60% homologues to GLL protein, sb03g042840 in sorghum was an orthologous protein to GLL. Rescuing experiment demonstrated spraying exogenous methyl jasmonate (MeJA) cannot recover the mutant phenotype of gll, it hinted that GLL is may not be correlated with JA signal pathway which regulated floral development.3. Agronomic traits of grain morphology, appearance quality, processing quality, eating quality, nutritional quality, germination rate, chlorophyll concentration and photosynthesis were analyzed using EG and OG mutant phenotype on two backgrounds of Yin2-3 and H604. The results showed that GLL gene mutation leads to shorter grain length, wider grain width, thicker grain thickness, smaller in length/width. Chalkiness percentage and chalkiness were changed different as in different backgrounds. In EG phenotype, the chalkiness percentage and chalkiness were decreased, but had no significant change in OG phenotype. The percentage of brown rice and milled rice were declined, while the percentage of head rice was increased in mutant lines. The protein content of EG phenotype increased significantly while did not change obviously in OG phenotype. The germination rate of OG phenotype declined obviously and there is no change in EG phenotype. On Yin2-3 background, the chlorophyll concentration decreased significantly while it increased in EG phenotype and have no change in OG phenotype under H604 background. The photosynthetic capacity and instantaneous water using efficiency (WUE) were enhanced in flowering stage, while it was increased or decreased in grain filling and maturity stage as different backgrounds of H604 or Yin2-3. The results provide an important theoretical basis for using gll mutant in future breeding. |
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