Sixteen microsatellite loci were isolated from lychee (Litchi chinensis), all of which exhibited polymorphism (two or three alleles per locus), with levels of heterozygosity ranging from 0.021 to 0.900. These loci can help assess the genetic structure of lychee. 相似文献
L-valine is an essential branched-chain amino acid that cannot be synthesized by the human body and has a wide range of applications in food, medicine and feed. Market demand has stimulated people’s interest in the industrial production of L-valine. At present, the mutagenized or engineered Corynebacterium glutamicum is an effective microbial cell factory for producing L-valine. Because the biosynthetic pathway and metabolic network of L-valine are intricate and strictly regulated by a variety of key enzymes and genes, highly targeted metabolic engineering can no longer meet the demand for efficient biosynthesis of L-valine. In recent years, the development of omics technology has promoted the upgrading of traditional metabolic engineering to systematic metabolic engineering. This whole-cell-scale transformation strategy has become a productive method for developing L-valine producing strains. This review provides an overview of the biosynthesis and regulation mechanism of L-valine, and summarizes the current metabolic engineering techniques and strategies for constructing L-valine high-producing strains. Finally, the opinion of constructing a cell factory for efficiently biosynthesizing L-valine was proposed.
由于青藏高原高海拔、低温的特殊环境,使得生态系统呼吸(RE)对气候变化的响应极其敏感,然而对高寒湿地生态系统长时间尺度上的RE动态特征及驱动机制的研究相对薄弱。以青藏高原东北部高寒湿地为研究对象,分析了基于涡度相关系统观测的高寒湿地2004—2016年的CO2通量排放动态及影响机制,对预测高寒湿地碳平衡对未来气候变化的响应具有重要意义。结果表明:高寒湿地在2004—2016年的月平均RE表现为单峰变化趋势,在8月达到峰值;年RE表现为逐年升高的趋势(P<0.05),年RE均值为(608.9±65.6) g C m-2 a-1;生长季RE约是非生长季RE的2.7倍,线性回归分析表明生长季RE(r~2=0.66,P=0.001)、非生长季RE(r~2=0.47,P=0.01)与全年RE呈极显著正相关。在月尺度上,分类回归树分析和线性回归分析表明土壤温度是月RE的最主要控制因素,暗示高寒湿地的土壤呼吸对整个生态系统的碳排放至关重要。在年际尺度上,生长季积温与生长季RE呈显著正相关(P<0.05),而生长季降水(PP... 相似文献