Analysis of Chloroplast Ultrastructure, Photosystem Ⅱ Light Harvesting Complexes and Chlorophyll Synthesis in a Chlorophyll-Less Rice Mutant W2555

The biosynthesis of chlorophyll comprises a number of challenging topics, while the mutants of higher plants are convenient models to study the biosynthesis of chlorophyll, photosynthetic activity, the spectral, biochemical, ultrastructural and genetic characteristics of chloroplasts. A great diversity of these mutants makes it difficult to classify them by phenotypes, as analogous phenotypes may result from many different mutations. Mutants can be used as an important tool to elucidate the fu…     

Cadmium Accumulation and Its Toxicity in Brittle Culm 1 （bcl）, a Fragile Rice Mutant

Cadmium （Cd） accumulation and toxicity in rice plants were characterized and identified by using brittle culm 1 （bcl）, a fragile rice mutant and its wild type （Shuangkezao, an indica rice） as materials by hydroponics. The low Cd level didn＇t obviously affect the growth parameters in both rice genotypes, but under high Cd levels （1.0 and 5.0 μmol/L）, the growth of both rice plants were substantially inhibited. Moreover, bcl tended to suffer more seriously from Cd toxicity than Shuangkezao. Cd accumulation in both rice plants increased with the increase of Cd levels. There was a significant difference in Cd accumulation between the two rice genotypes with constantly higher Cd concentration in bcl, which also accumulated more Cd at 0, 0.1, and 1.0 μmol/L Cd levels. The same case was found in the two rice plants grown on Cd-contaminated soil. This suggested that cell wall might play an important role in Cd accumulation in rice plants by the physiological mechanisms. The malondialdehyde （MDA） content, superoxide dismutase （SOD） and peroxidase （POD） activities in rice plants were affected differently under Cd treatments, and which implied that POD might play the main role in detoxifying active oxygen free radical. A significant difference in antioxidative system between the two rice genotypes was found with constantly higher MDA content, SOD and POD activities in bcl. In summary, bcl accumulated more Cd and appeared to be more sensitive to Cd stress compared with its wild type.     

Genetic Analysis and Preliminary Mapping of Two Recessive Resistance Genes to Brown Planthopper, Nilaparvata lugens Stl in Rice

An F2 population derived from the cross of WB01, an introgression line resistant to brown planthopper (BPH) originated from Oryza rufipogon Griff. and a susceptible indica variety 9311, was developed for genetic analysis and gene mapping. The population with 303 F2:3 families was genotyped by 141 simple sequence repeat (SSR) markers and used for gene mapping. Two softwares, Mapmaker/Exp 3.0 and Windows QTL Cartographer V2.0 were applied to detect QTLs. Totally, two QTLs resistant to BPH, named temporarily a...     

Genetic Analysis and Preliminary Mapping of Two Recessive Resistance Genes to Brown Planthopper,Nilaparvata lugens Stl in Rice

An F2 population derived from the cross of WB01, an introgression line resistant to brown planthopper (BPH) originated from Oryza rufipogon Griff. and a susceptible indica variety 9311, was developed for genetic analysis and gene mapping. The population with 303 F2:3 families was genotyped by 141 simple sequence repeat (SSR) markers and used for gene mapping. Two softwares, Mapmaker/Exp 3.0 and Windows QTL Cartographer V2.0 were applied to detect QTLs. Totally, two QTLs resistant to BPH, named temporarily a...     

Natural Homologous Triploidization and DNA Methylation in SARII-628, a Twin-seedling Line of Rice （Oryza sativa）

A total of five pairs of diploid-triploid twin-seedlings (a diploid seedling and a triploid seedling emerged from a grain) were selected out from 4500 pairs of seedlings from SARII-628, a twin-seedling rice line. SSR analysis indicated that no difference between the diploid seedling and corresponding triploid seedling in a twin-seedling was found at the 310 loci, indicating that there was no obvious change in DNA primary structure. A modified AFLP technique ‘MSAP (methylation-sensitive AFLP)’ was used to analyze methylation mutation. Although no methylation mutation was noted among the five diploids, 29 methylation mutation loci were found from the corresponding triploids. This suggested that methylation mutation happened rapidly on M0 generation after natural homologous triploidization. The mutations were classified into 10 types, including 3 increased types, 3 decreased types and 4 undecided types of methylation-degrees. The bands of 22 loci were sequenced and then those sequences were searched through website. The result showed that the methylation mutation involved into the whole rice genome and the 12 pairs of chromosomes. The mutation trend was site-related and there were different mutation loci for different triploids, which foretold that SARII-628 would have different evolution fates after natural homologous triploidization.