Fine mapping of a quantitative trait locus for grain number per panicle from wild rice (Oryza rufipogon Griff.)

SIL040, an introgression line (IL) developed by introgressing chromosomal segments from an accession of Oryza rufipogon into an indica cultivar Guichao 2, showed significantly less grains per panicle than the recurrent parent Guichao 2. Quantitative trait locus (QTL) analysis in F₂ and F₃ generations derived from the cross between SIL040 and Guichao 2 revealed that gpa7, a QTL located on the short arm of chromosome 7, was responsible of this variation. Alleles from O. rufipogon decreased grains per panicle. To fine mapping of gpa7, a high-resolution map with 1,966 F₂ plants derived from the cross between SIL040 and Guichao 2 using markers flanking gpa7 was constructed, and detailed quantitative evaluation of the structure of main panicle of each of F₃ families derived from recombinants screened was performed. By two-step substitution mapping, gpa7 was finally narrowed down to a 35-kb region that contains five predicted genes in cultivated rice. The fact that QTLs for five panicle traits (length of panicle, primary branches per panicle, secondary branches per panicle, grains on primary branches and grains on secondary branches) were all mapped in the same interval as that for gpa7 suggested that this locus was associated with panicle structure, showing pleiotropic effects. The characterizing of panicle structure of IL SIL040 further revealed that, during the domestication from common wild allele to cultivated rice one at gpa7, not only the number of branches and grains per panicle increased significantly, more importantly, but also the ratio of secondary branches per panicle to total branches per panicle and the ratio of grains on secondary branches per panicle to total grains per panicle increased significantly. All these results reinforced the idea that gpa7 might play an important role in the regulation of grain number per panicle and the ratio of secondary branches per panicle during the domestication of rice panicle.Feng Tian and Zuo Feng Zhu contributed equally to this work.     

布鲁氏菌L7/L12蛋白的基因克隆与原核表达

本研究对羊布鲁氏菌L7/L12蛋白进行了表达和纯化。首先从布鲁氏菌M5基因组中克隆L7/L12目的基因片段,连接至pMD-19T载体,转化入E.coli DH5α感受态细胞,PCR鉴定及测序鉴定正确后对其进行双酶切,构建重组质粒pGEX-6P-1-L7/L12并利用E.coli BL21(DE3)进行诱导表达。羊布鲁氏菌L7/L12基因片段大小为375 bp。SDS-PAGE检测蛋白大小为13 kD,与预测值相符。Western blotting方法检测其免疫学特性。实验结果表明,成功构建了pGEX-6P-1-L7/L12原核表达载体,并在大肠杆菌中成功表达了L7/L12重组蛋白,Western blotting法检测其具有免疫反应。本实验为下一步研究蛋白功能及布鲁氏菌新型疫苗的研制提供了实验基础。     

The Pathological Phenotypes of Human TDP-43 Transgenic Mouse Models Are Independent of Downregulation of Mouse Tdp-43

Tar DNA binding protein 43 (TDP-43) is the major component of pathological deposits in frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) and in amyotrophic lateral sclerosis (ALS). It has been reported that TDP-43 transgenic mouse models expressing human TDP-43 wild-type or ALS-associated mutations recapitulate certain ALS and FTLD pathological phenotypes. Of note, expression of human TDP-43 (hTDP-43) reduces the levels of mouse Tdp-43 (mTdp-43). However, it remained unclear whether the mechanisms through which TDP-43 induces ALS or FTLD-like pathologies resulted from a reduction in mTdp-43, an increase in hTDP-43, or a combination of both. In elucidating the role of mTdp-43 and hTDP-43 in hTDP-43 transgenic mice, we observed that reduction of mTdp-43 in non-transgenic mice by intraventricular brain injection of AAV1-shTardbp leads to a dramatic increase in the levels of splicing variants of mouse sortilin 1 and translin. However, the levels of these two abnormal splicing variants are not increased in hTDP-43 transgenic mice despite significant downregulation of mTdp-43 in these mice. Moreover, further downregulation of mTdp-43 in hTDP-43 hemizygous mice, which are asymptomatic, to the levels equivalent to that of mTdp-43 in hTDP-43 homozygous mice does not induce the pathological phenotypes observed in the homozygous mice. Lastly, the number of dendritic spines and the RNA levels of TDP-43 RNA targets critical for synapse formation and function are significantly decreased in symptomatic homozygous mice. Together, our findings indicate that mTdp-43 downregulation does not lead to a loss of function mechanism or account for the pathological phenotypes observed in hTDP-43 homozygous mice because hTDP-43 compensates for the reduction, and associated functions of mTdp-43. Rather, expression of hTDP-43 beyond a certain threshold leads to abnormal metabolism of TDP-43 RNA targets critical for neuronal structure and function, which might be responsible for the ALS or FTLD-like pathologies observed in homozygous hTDP-43 transgenic mice.     

基于TM影像的白云岩与石灰岩上喀斯特植被时空变化差异研究

喀斯特土壤主要由白云岩和石灰岩风化而来,植被生长及其分布究竟怎样响应这一特殊地质背景?以人为干扰影响较小的喀斯特自然保护区为研究对象,采用监督分类法对1990年和2011年两期TM影像进行植被分类,并利用景观格局分析方法研究两种岩性上植被变化差异。结果表明,1990年和2011年研究区内两种母岩上均以乔木林和乔灌为主,草灌和草丛分布少,白云岩上乔木林的面积比例大于石灰岩上的比例,而草灌和草丛小于石灰岩上的比例;近20年来白云岩与石灰岩上草丛、草灌、灌丛和乔灌均以正向演替为主,但白云岩上正向演替比例大于石灰岩上的比例;两种岩性上植被斑块连接性均增强、破碎程度均降低,白云岩上植被斑块的破碎化程度和多样性指数较石灰岩上低,内部连接性强。由此可见,喀斯特白云岩较石灰岩有利于草丛、草灌的自然恢复,岩性引起的水土资源配置和养分地球化学循环过程差异制约着喀斯特地区植被的时空格局。     

喀斯特石漠化综合治理及其区域恢复效应

国家加大生态保护与建设力度背景下,我国西南喀斯特石漠化面积实现"持续净减少",面临由传统高强度人为干扰向大规模自然恢复与人工造林的转变,石漠化治理也面临转型。现有喀斯特生态研究已阐明了喀斯特脆弱生态系统人为干扰退化机制,初步揭示了生态治理改善生态系统结构与功能的恢复机理,突破了保土集水与植被恢复的适应性石漠化治理技术与模式,评估了石漠化治理显著加速区域植被生长与恢复的固碳效应。但目前石漠化治理面临着治理成效巩固困难、治理技术与模式缺乏区域针对性、大规模低效人工林亟待改造、社会人文驱动机制不清等问题。未来喀斯特生态恢复应聚焦石漠化治理提质增效,从侧重单一生态要素、单一生态过程的研究向多要素综合、多过程综合以及喀斯特地表-地下过程耦合、景观格局与生态过程耦合、生态过程与生态系统服务耦合、自然与人文过程耦合等陆地表层系统集成的方向发展,为我国西南喀斯特地区石漠化治理与扶贫开发成效巩固、乡村振兴与美丽中国战略的实施提供科技支撑。     

Polymorphism at the esterase isozyme locus Est10 associated with phylogenetic differentiation in rice

A new esterase isozyme locus, Est10, with 6 alleles including the null form, has been found in rice by using polyacrylamide gel electrophoresis. Thirty F(2) populations of all possible combinations between 5 different band morphs were studied. The segregation pattern indicated that bands 1, 2, 3, 4, and the null form (0) were allelic with each other. The alleles of Est10 were distributed at different frequencies among different varietal groups of rice and also between cultivated rice and its wild relatives (Oryza rufipogon Griff.). Alleles 1 and 2 were frequently found in Japonica and Indica types, respectively. Allele 3 showed a high frequency in Aus and Boro, both Indica types cultivated in South Asia. Allele 4 was frequent in wild rice O. rufipogon. Judging from the linkage between Est10 and RFLP marker RG220 and isozyme marker Est5, Est10 is located on chromosome 1. The importance of this locus in evolutionary studies of rice is discussed.     

Enhanced Glucosamine Production with Actinomucor elegans Based on Stimulating Factor of Methanol

Glucosamine (GlcN) is a major and valuable component in the cell wall of fungi. In this study, the cell wall was treated via a two-stage alkali and acid process, and chitin and chitosan were fully deacetylated, partially depolymerized, and converted to GlcN oligosaccharides. Then, the oligosaccharides were analyzed by high performance liquid chromatography. The influences of Actinomucor elegans on GlcN production in a flask culture were investigated to achieve an optimum yield of GlcN. The experimental result showed that cultivation in condition of pH 6.0, 100 mL working volume (500 mL flask), 10 % (v/v) inoculum concentration, at 28 °C and 200 rpm for 6 days yielded highest dry cell weight (DCW) which was 23.43 g L⁻¹, with a GlcN concentration of 5.12 g L⁻¹. Methanol as stimulating factor was found to exert the best effect in concentration of 1.5 % (v/v). With addition of methanol into medium, the DCW increased from 23.69 to 32.42 g L⁻¹, leading to maximum GlcN concentration of 6.85 g L⁻¹ obtained. Here, the methanol addition may be useful for industrial production of GlcN, and may also be meaningful for the production of other fine chemicals by filamentous fungi.     

Degradation Model of Bioabsorbable Cardiovascular Stents

This study established a numerical model to investigate the degradation mechanism and behavior of bioabsorbable cardiovascular stents. In order to generate the constitutive degradation material model, the degradation characteristics were characterized with user-defined field variables. The radial strength bench test and analysis were used to verify the material model. In order to validate the numerical degradation model, in vitro bench test and in vivo implantation studies were conducted under physiological and normal conditions. The results showed that six months of degradation had not influenced the thermodynamic properties and mechanical integrity of the stent while the molecular weight of the stents implanted in the in vivo and in vitro models had decreased to 61.8% and 68.5% respectively after six month''s implantation. It was also found that the degradation rate, critical locations and changes in diameter of the stents in the numerical model were in good consistency in both in vivo and in vitro studies. It implies that the numerical degradation model could provide useful physical insights and prediction of the stent degradation behavior and evaluate, to some extent, the in-vivo performance of the stent. This model could eventually be used for design and optimization of bioabsorbable stent.