大肠杆菌yigP基因转录调控序列的鉴定

【目的】调查yigP基因启动子的活性,并对该转录调控序列进行分析。【方法】以lacZ为报告基因,克隆启动子片段至启动子探针质粒中,通过检测β-半乳糖苷酶活性判断启动子活性,并通过克隆一系列逐步缩短的启动子片段来确定启动子所在区域。利用定点突变技术,对启动子的重要序列进行定点突变,调查其对启动子活性的影响。【结果】确定了yigP基因启动子的区域,鉴定了启动子的-10区和-35区,并发现了启动子上游存在一个负调控序列,对该序列进行了初步的研究显示其中部分序列是这种负调控作用的核心序列。【结论】对yigP基因的转录调控序列进行了鉴定,丰富了我们对基因转录调控的认识。     

Large‐scale GWAS in sorghum reveals common genetic control of grain size among cereals

Grain size is a key yield component of cereal crops and a major quality attribute. It is determined by a genotype’s genetic potential and its capacity to fill the grains. This study aims to dissect the genetic architecture of grain size in sorghum. An integrated genome‐wide association study (GWAS) was conducted using a diversity panel (n = 837) and a BC‐NAM population (n = 1421). To isolate genetic effects associated with genetic potential of grain size, rather than the genotype’s capacity to fill the grains, a treatment of removing half of the panicle was imposed during flowering. Extensive and highly heritable variation in grain size was observed in both populations in 5 field trials, and 81 grain size QTL were identified in subsequent GWAS. These QTL were enriched for orthologues of known grain size genes in rice and maize, and had significant overlap with SNPs associated with grain size in rice and maize, supporting common genetic control of this trait among cereals. Grain size genes with opposite effect on grain number were less likely to overlap with the grain size QTL from this study, indicating the treatment facilitated identification of genetic regions related to the genetic potential of grain size. These results enhance understanding of the genetic architecture of grain size in cereal, and pave the way for exploration of underlying molecular mechanisms and manipulation of this trait in breeding practices.     

Comparative analysis of anoxic coleoptile elongation in rice varieties: relationship between coleoptile length and carbohydrate levels, fermentative metabolism and anaerobic gene expression

Rice ( Oryza sativa L.) seeds can germinate under anoxia and can show coleoptile elongation. The anoxic coleoptile is usually longer than aerobic coleoptiles. Although several hypotheses have been proposed to explain the ability of rice to elongate coleoptiles under anoxia, conclusive experimental evidence explaining this physiological trait is lacking. In order to investigate whether metabolic and molecular markers correlate with anoxic coleoptile length, we screened 141 Italian and 23 Sri Lankan rice cultivars for their ability to elongate coleoptiles under anoxia. Differences in anoxic coleoptile length were used to evaluate whether a correlation exists between coleoptile length and biochemical and molecular parameters. The expression of genes coding for glycolytic and fermentative enzymes showed a very low correlation with anoxic coleoptile length. Although differences were found in carbohydrate content between the varieties tested, this parameter also does not appear to be critical in terms of coleoptile elongation. Efficient ethanol fermentation does, however, correlate well with the elongation of coleoptiles under anoxic conditions.     

Systematic phenome analysis of Escherichia coli multiple‐knockout mutants reveals hidden reactions in central carbon metabolism

Central carbon metabolism is a basic and exhaustively analyzed pathway. However, the intrinsic robustness of the pathway might still conceal uncharacterized reactions. To test this hypothesis, we constructed systematic multiple‐knockout mutants involved in central carbon catabolism in Escherichia coli and tested their growth under 12 different nutrient conditions. Differences between in silico predictions and experimental growth indicated that unreported reactions existed within this extensively analyzed metabolic network. These putative reactions were then confirmed by metabolome analysis and in vitro enzymatic assays. Novel reactions regarding the breakdown of sedoheptulose‐7‐phosphate to erythrose‐4‐phosphate and dihydroxyacetone phosphate were observed in transaldolase‐deficient mutants, without any noticeable changes in gene expression. These reactions, triggered by an accumulation of sedoheptulose‐7‐phosphate, were catalyzed by the universally conserved glycolytic enzymes ATP‐dependent phosphofructokinase and aldolase. The emergence of an alternative pathway not requiring any changes in gene expression, but rather relying on the accumulation of an intermediate metabolite may be a novel mechanism mediating the robustness of these metabolic networks.