| Rice is an important food crop, plant height is one of the important agronomic traits, its plant height is of great significance of rice production stable and high yield.Therefore, identification and create new dwarf mutant, to further reveal the molecular regulation mechanism of rice plant height growth and development is of great significance. One small seed and dwarf mutant dss-1 was identified from guizhou lipingzabianhe which seeds were treated by ethyl methanesulfonate(EMS), and the phenotype, photosynthetic charateristics, internode cell structure, sensitivity of BR and transcript levels of BR genes in dss-1 were investigated and analyzed. To analyze the genetic characteristics, the dss-1 mutant was crossed with different varieties to construct hybrid population to analyze the genetic characteristic and the dss-1 gene was initial mapped. The results showed were as follow:1 The agronomic trait and cytological analysis of the dss-1The dss-1 mutant exhibited dwarf, plant-type erect, little dark green leaves,shorter the second internode cells, small and round grains, spike length longer and the first internode length increased. The dss-1 mutant plant height is 98 cm, which is 48%(205.18 cm) at mature stage. The epidermal cell length of the second leaf sheath and leaf in dss-1 mutant were significantly shortened at the 2 weeks of seedling age. each internode cell of the dss-1 observation found that the fisrt, third, four internode of the dss-1 is no difference between the cell morphology, cell length changed little; the second internode cells length shorter and circle compared with wild type, which indicated that the second internode shortened is due to the cell length shorter.2 Response to exogenous GA and BR of the dss-1 mutantThe dss-1 mutant and wild type by GA3 treatment grain without endosperm wereall can induce expression of ?- amylase, which indicated that the mutant gene not related to the GA signaling pathway.The second leaf sheath length of the dss-1mutant and wild type seedling were by GA3 treatment, mutant and wild type seedling second leaf sheath length not return to the wild type, which showed that mutant is not sensitive to exogenous GA3, speculated that the mutant gene not related to the GA synthesis pathway. When dss-1 grown in complete darkness, the mesocotyl not elongated in the mutants indicated that dark morphogenesis of the dss-1 mutant is affected. The dss-1 show insensitive by BL spraged the seedling indicated that the mutant could be BR biosynthesis to the defects caused by mutations.3 Photosynthetic physiological characteristics of the dss-1 mutantTo explore the physiological and biochemical differences of dss-1mutant was identified from Guizhou lipingzabianhe, we determined to protect activity,photosynthetic physiological characteristics in dss-1 mutant were analyzed using LI-6400 photosynthetic system. The results showed that the dss-1 mutant SOD, POD and CAT activity were 8.12 U/mg(prot), 28.60 U/mg(prot), 23.77 U/mg(prot), they were slightly high than wild type [SOD 7.75 U/mg(prot), POD is 27.23 U/mg(prot)and the CAT is 21.76 U/mg(prot)], but did not reach significant difference levels, the result shows that the dss-1 is not associated with antioxidant enzymes. MDA content was 0.90 nmol·mg-1(FW), which were increased 58% compared with wild type,reached significant difference level. The net photosynthetic rate(8.9 ?mol·m-2·s-1)and the chlorophyll content(5.7 mg·g-1·FW) in the dss-1 mutant were increased24.72% and 37.5% compared with wild type(The net photosynthetic rate 6.7?mol·m-2·s-1, the chlorophyll content 3.0 mg·g-1·FW) at mature stage; the net photosynthetic rate(18.7 ?mol·m-2·s-1) and the chlorophyll content(4.8 mg·g-1·FW)in the dss-1 mutant were 10.16% and 21.05% compared with wild type(The net photosynthetic rate was 8.9 ?mol·m-2·s-1 and the chlorophyll content was 5.7mg·g-1·FW) at tillering stage. The initial fluorescence yield(Fo) was 175.1 and the maximum photosynthetic efficiency(Fv/Fm) of dss-1 mutant were 19.50% and 1.3%compared with wild type(Fo was 141.01, Fv /Fm was 0.78), electron transport rate(ETR), photochemical efficiency of PSII(?PSII) and photochemical quenching(q P)were 96.73, 0.16, 0.71, they were decreased compared with wild type(106.13, 0.20,0.75). The MAD content was 0.90 nmol·mg-1(FW), it was 58% compared with wild type constantly. The dwarf mutant gene can have some relevance with the dss-1mutant physiological and biochemical differences and phenotype characteristics.4 Expression of BR biosynthesis and signal transduction relative genes of dss-1 mutantUsing real-time PCR detected transcript levels of the BR synthesis and signal transduction raleative genes in mutant and wild type at seedling stage, transcript levels of the BR synthesis raleative genes( DWARF4, DWARF, D11, DWARF2)and the signal BR raleative genes(BRI1, MDP1, RAG1, BZR1) were all up-regulation in mutant dss-1 compared with wild type, the synthesis gene DWARF of the most significant up-regulation gene is 7.8 times compared with wild type. Expression of signal transduction pathways relative gene BRI1 is about 5.3 times compared with wild type. BR raleative gene expression up-regulation were higher than 2 times, but not DWARF4, RGA1, MDP1 on this basis. The results was found that the dss-1 is not DWARF4, DWARF, D11, DWARF2 in BR biosynthesis, nor one of BRI1, MDP1,RAG1, BZR1 in BR signaling pathway, but a BR biosynthesis of related genes.5 Genetic analysis and gene mapping of the dss-1 mutantWe has been build dss-1 and 9311, yinguizhan, wild type of Guizhou lipingzabianhe 3 groups of cross combinations, The plant heights of F1 individuals were measured. The segregation ratios were investigated in F2 populations from the crosses between dss-1/wild type, dss-1/yinguizhan and dss-1/9311, Mapping was viewed as F2 populations from the cross dss-1/9311. The results found that all the F1 progenies were showed a similar height phenotype to the normal plants. The segregation ratio of F2 progenies from dss-1/wild type, dss-1/9311 and dss-1/yinguizhan were fitted the expected ratio of 3:1(normal plant: dwarf plant).These indicated that dss-1 was controlled by a single recessive gene, Preliminary named Dss- 1. Using SSR molecular marker amplified mutant in the gene pool, the results showed that there existed chain relationship between the rice chromosome 3marker RM15238 and RM15521 with the target gene, preliminary positioning the mutant gene of dss-1 on 3 chromosome marker RM15238 near 16.72-20.83 and RM15521 near 22.29-26.47 zone. |
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