Pachytene piRNAs instruct massive mRNA elimination during late spermiogenesis

Spermatogenesis in mammals is characterized by two waves of piRNA expression: one corresponds to classic piRNAs responsible for silencing retrotransponsons and the second wave is predominantly derived from nontransposon intergenic regions in pachytene spermatocytes, but the function of these pachytene piRNAs is largely unknown. Here, we report the involvement of pachytene piRNAs in instructing massive mRNA elimination in mouse elongating spermatids (ES). We demonstrate that a piRNA-induced silencing complex (pi-RISC) containing murine PIWI (MIWI) and deadenylase CAF1 is selectively assembled in ES, which is responsible for inducing mRNA deadenylation and decay via a mechanism that resembles the action of miRNAs in somatic cells. Such a highly orchestrated program appears to take full advantage of the enormous repertoire of diversified targeting capacity of pachytene piRNAs derived from nontransposon intergenic regions. These findings suggest that pachytene piRNAs are responsible for inactivating vast cellular programs in preparation for sperm production from ES.     

Temporal changes in climatic variables and their impact on crop yields in southwestern China

Knowledge of variability in climatic variables changes and its impact on crop yields is important for farmers and policy makers, especially in southwestern China where rainfed agriculture is dominant. In the current study, six climatic parameters (mean temperature, rainfall, relative humidity, sunshine hours, temperature difference, and rainy days) and aggregated yields of three main crops (rice: Oryza sativa L., oilseed rape: Brassica napus L., and tobacco: Nicotiana tabacum L.) during 1985–2010 were collected and analyzed for Chongqing—a large agricultural municipality of China. Climatic variables changes were detected by Mann-Kendall test. Increased mean temperature and temperature difference and decreased relative humidity were found in annual and oilseed rape growth time series (P?<?0.05). Increased sunshine hours were observed during the oilseed rape growth period (P?<?0.05). Rainy days decreased slightly in annual and oilseed rape growth time series (P?<?0.10). Correlation analysis showed that yields of all three crops could benefit from changes in climatic variables in this region. Yield of rice increased with rainfall (P?<?0.10). Yield of oilseed rape increased with mean temperature and temperature difference but decreased with relative humidity (P?<?0.01). Tobacco yield increased with mean temperature (P?<?0.05). Path analysis provided additional information about the importance and contribution paths of climatic variables to crop yields. Temperature difference and sunshine hours had higher direct and indirect effects via other climatic variables on yields of rice and tobacco. Mean temperature, relative humidity, rainy days, and temperature difference had higher direct and indirect effects via others on yield of oilseed rape.     

中国人COL2A1基因座的扩增片段长度多态性

用聚合酶链式反应、高分辨聚丙烯酰胺凝胶水平电泳及银染技术对位于人类Ⅱ型胶原基因终止密码下游非转录区１．３ｋｂ处的可主数目串联重复育列进行了研究。制备了由人类不同基因型ＤＮＡ混合而成的人类等位基因型参考物，根据实验结果进行了命名。