Fine mapping and marker-assisted selection (MAS) of a low glutelin content gene in rice

Rice with low glutelin content is suitable as functional food for patients affected with diabetes and kidney failure. The fine mapping of the gene(s) responsible for low glutelin content will provide information regarding the distribution of glutelin related genes in rice genome and will generate markers for the selection of low glutelin rice varieties. Following an SDS-PAGE screen of rice germplasm from Taihu Valley of China, Japonica selection W3660 is identified to be a novel mutant characterized with low glutelin content. For fine mapping the mutant gene for low glutelin content, F2 and F3 populations were derived from a cross between W3660 and Jingrennuo. SDS-PAGE analysis of the total endosperm protein showed that the low glutelin content trait was controlled by a single dominant nuclear gene. Genetic mapping, using SSRs, located this gene to chromosome 2, in the region between SSR2-001/SSR2-004 and RM1358. The dis- tances of the two markers to the target gene were 1.1 cM and 3.8 cM respectively. By semi-quantitative RT-PCR analysis, the transcripts of GluB4/GluB5 genes located within the region do not change. However, GluB5 gene located proximal to SSR2-001/SSR2-004 was specifically reduced. SSR profiles of seven Japonica varieties were compared with that of W3660 for loci in the relevant genetic region. The markers SSR2-004 and RM1358 were used for marker- assisted selection. The selection efficiencies of SSR2-004 and RM1358 were 96.8% and 92.7% respectively. This provides a standard starting point for the breeding of low glutelin content rice varieties in China.

Inferring the invasion mechanisms of the red swamp crayfish in China using mitochondrial DNA sequences

The red swamp crayfish,Procambarus clarkii,is a native species in north-eastern Mexico and south-central USA.P.clarkii was introduced to China in 1929 and has been used as an aquaculture species in China since 1983.It currently exists in most of the provinces of China,but threatens local fish,crustaceans,aquatic plants and local freshwater ecosystems.We examined the genetic variation in partial mitochondrial ND2 gene of 831 individuals collected from 25 P.clarkii populations in 13 provinces of China to infer the expansion pathways and mechanisms.Six haplotypes were detected.All six haplotypes appeared in four populations in Nanjing and a population located near Nanjing whereas only 1–5 of the six haplotypes were present in other populations.These data suggest that the populations in Nanjing are probably the source of all other populations in China.There were no significant relationships between geographic distances and genetic distances in 25 populations,whereas significant relationship was found in four populations in Qinhuai River covering 50 km in Nanjing.These data suggest that the expansion mainly be human-mediated in large scale,and active disposal or non-anthropogenic passive dispersal might have played an important role in expansion at a smaller scale.In some places far away from Nanjing,several haplotypes existed,suggested multiple introduction events may have happened.Although aquaculture of this species could bring huge economic benefit,its potential to negatively affect native biota and entire ecosystems should not be ignored.