扎龙湿地芦苇种群不同龄级根茎构件的季节动态

克隆植物根茎具有营养繁殖和扩展种群的功能,也是芽和分株生理整合的通道。根茎构件具有出生、死亡及年龄等种群统计特征,不同龄级根茎的季节动态可以反映根茎的存活和衰老过程。采用单位土体挖掘取样,对扎龙湿地4个生境芦苇种群根茎构件进行野外调查,比较不同龄级根茎长度、生物量和干物质贮量的季节动态。结果表明:7—10月份,1a根茎长度、生物量和干物质贮量均呈指数函数增加,在生长季中后期有一个持续时间较长的生长和物质积累时期。6—10月份,2a、3a根茎长度呈线性函数增加,4—6a根茎长度呈线性函数减少;2—4a根茎生物量和2—5a根茎干物质贮量呈二次函数先减少后增加,5a、6a根茎生物量和6a根茎干物质贮量呈幂函数减少。整个生长期内,根茎长度和根茎生物量均以3a最大,根茎长度以最高的6a最小,根茎生物量以最低的1a最小;根茎干物质储量以5a最大,以最低的1a最小。4个生境芦苇种群根茎长度、生物量和干物质贮量在龄级间的差异及差异序位稳定,在新根茎的产生、老根茎的存活以及根茎寿命与养分消耗和储藏上均具有稳定的生物学特性,不同龄级根茎在种群中的地位和作用以及对种群的贡献不同。     

嗜热细菌Clostridium thermocellum阿魏酸酯酶基因的克隆、异源表达及酶学特性分析

【目的】阐明嗜热细菌Clostridium thermocellum Xyn Z蛋白的阿魏酸酯酶催化域的酶学特性,为其在生物质能源及其它发酵工业中的应用奠定基础。【方法】分别构建了C.thermocellum Xyn Z的阿魏酸酯酶催化域(FAE)及该阿魏酸酯酶催化域和碳水化合物结合域(FAE-CBM6)编码基因的原核表达载体,并在大肠杆菌菌株BL21(DE3)中异源表达,在此基础上分析比较了温度、pH、底物、金属离子及CBM6结合域对阿魏酸酯酶活性的影响。【结果】重组FAE酶及FAE-CBM6酶发挥催化活性的适宜pH值为5.0-9.0,适宜温度为50-70°C,它们对不同金属离子的响应有差异。【结论】在同一反应条件下,FAE-CBM6酶的酶活均比FAE高,说明CBM6结合域的存在对于阿魏酸酯酶活性有促进作用。     

荒漠植物白刺属4个物种的生殖分配比较

选定乌兰布和沙漠地区白刺属4种植物为研究对象,通过对其样株在花期的各生殖构件的数量特征及生物量调查,系统研究了唐古特白刺(Nitraria tangutorum Bobr.)、西伯利亚白刺(Nitraria sibirica Pall.)、大白刺(Nitraria roborowskii Kom.)和泡泡刺(Nitraria sphaerocarpa Maxim.)4种白刺属植物在生殖枝水平上的生殖分配。结果表明:不同白刺属植物在分株高度、生殖枝长、生殖枝基径、单枝花数、花序干重、枝叶干重等生殖构件的数量性状方面均有显著差异,其中泡泡刺的各生殖构件的数量均最小;除了西伯利亚白刺的生殖分配值达到44.51%外,其余3种白刺的生殖分配值均没有超过20%。经统计分析,4种白刺种群的生殖枝长分别与分株高度呈显著(P<0.05)的直线性正相关关系;生殖枝花序干重与分株高显著正相关;4种白刺的生殖分配随着分株生殖枝生物量的增加而减少,即白刺的个体大小与生殖分配之间呈现负相关关系。这种生殖分配特点反映了不同白刺植物对生长环境的资源利用、与克隆繁殖的权衡及对生态适应的策略。     

川产淫羊藿属（Epimedium）药用植物的无性系构件特征和生物量配置比较

在构件水平上,对川产的3种药用淫羊藿属植物（淫羊藿（Epimedium brevicornu）、箭叶淫羊藿（E.sagittatum）、柔毛淫羊藿（E.pubescens））的无性系构件特征、克隆构型及构件生物量配置进行比较,结果表明在野生状态下：该属3个种无性系构件的形态特征差异显著,且存在较大的变异性,变异系数范围在29.29%~48.31%之间;箭叶淫羊藿更趋于“游击型”克隆构型,而淫羊藿和柔毛淫羊藿则更趋于“密集型”克隆构型;该属3个种都将高比例生物量配置到叶片或者根茎,其次为茎,再其次为根。柔毛淫羊藿具有更强的克隆繁殖能力,单位面积上各构件生物量均最大,应作为人工引种栽培的首选种。     

微生物源脂肽的生物合成和分子调控

微生物源脂肽具有抑制真菌和细菌的生长、抗病毒和抗肿瘤等多种生物活性,在农业生物防治、临床医疗、环境治理等多种领域具有巨大的应用潜力。然而,低产量一直是影响其推广应用的瓶颈。深入了解脂肽合成的关键因素和调控策略对于提高其产量和纯度至关重要。本文概括了3大家族脂肽surfactin、fengycin和iturin的结构、功能及应用前景,介绍了NRPS和NRPS-PKS两种合成系统的结构域和功能,阐释了脂肽生物合成过程中侧链脂肪酸的合成、脂肪酸的活化及与氨基酸的连接、肽链的延伸和环化三个阶段的模块组装和酶催化活动,以及三大家族脂肽合成操纵子开放阅读框的组成;总结了导入或缺失关键基因、定点突变、模块替换、强启动子替换、修饰前体路径等多种遗传操作对脂肽产量的影响,以及群体感应肽信息素、sigma因子等全局调控因子对脂肽合成基因表达的调节。指出利用多组学联用深入探讨脂肽合成的全局分子调控机制和加强结构域蛋白互作和分子动力学研究是提高脂肽产量和纯度以及创造新脂肽的理论基础,提出了利用基因组装和编辑等合成生物学方法及代谢工程技术提高脂肽产量和挖掘新型脂肽靶向性的可能途径,为推进脂肽的生产和应用进程提供科学参考。     

利用GeneHub软件分析人类染色体相邻基因的表达相关性

利用我们研制的基因信息融合分析软件GeneHub,按染色体开窗的方法将人类基因组沿着染色体划分为一系列基因群,用不同的相关测度(Pearson相关、Spearman秩相关、欧氏距离)考察这些基因群中所有基因间在二套独立的基因表达谱数据中的平均表达相关性。实验结果表明,与随机基因群相比,染色体上的邻近基因具有显著的表达相关性。约有40％的被检测基因包含于我们检测到的邻近相似表达基因群中。该现象提示真核生物中的基因存在模块化的共表达趋势。     

Half‐Heusler Thermoelectric Module with High Conversion Efficiency and High Power Density

Half‐Heusler (HH) compounds have shown great potential in waste heat recovery. Among them, p‐type NbFeSb and n‐type ZrNiSn based alloys have exhibited the best thermoelectric (TE) performance. However, TE devices based on NbFeSb‐based HH compounds are rarely studied. In this work, bulk volumes of p‐type (Nb_0.8Ta_0.2)_0.8Ti_0.2FeSb and n‐type Hf_0.5Zr_0.5NiSn_0.98Sb_0.02 compounds are successfully prepared with good phase purity, compositional homogeneity, and matchable TE performance. The peak zTs are higher than 1.0 at 973 K for Hf_0.5Zr_0.5NiSn_0.98Sb_0.02 and at 1200 K for (Nb_0.8Ta_0.2)_0.8Ti_0.2FeSb. Based on an optimal design by a full‐parameters 3D finite element model, a single stage TE module with 8 n‐p HH couples is assembled. A high conversion efficiency of 8.3% and high power density of 2.11 W cm^?2 are obtained when hot and cold side temperatures are 997 and 342 K, respectively. Compared to the previous TE module assembled by the same materials, the conversion efficiency is enhanced by 33%, while the power density is almost the same. Given the excellent mechanical robustness and thermal stability, matchable thermal expansion coefficient and TE properties of NbFeSb and ZrNiSn based HH alloys, this work demonstrates their great promise for power generation with both high conversion efficiency and high power density.     

The tetrameric pheromone module SteC‐MkkB‐MpkB‐SteD regulates asexual sporulation,sclerotia formation and aflatoxin production in Aspergillus flavus

For eukaryotes like fungi to regulate biological responses to environmental stimuli, various signalling cascades are utilized, like the highly conserved mitogen‐activated protein kinase (MAPK) pathways. In the model fungus Aspergillus nidulans, a MAPK pathway known as the pheromone module regulates development and the production of secondary metabolites (SMs). This pathway consists five proteins, the three kinases SteC, MkkB and MpkB, the adaptor SteD and the scaffold HamE. In this study, homologs of these five pheromone module proteins have been identified in the plant and human pathogenic fungus Aspergillus flavus. We have shown that a tetrameric complex consisting of the three kinases and the SteD adaptor is assembled in this species. It was observed that this complex assembles in the cytoplasm and that MpkB translocates into the nucleus. Deletion of steC, mkkB, mpkB or steD results in abolishment of both asexual sporulation and sclerotia production. This complex is required for the positive regulation of aflatoxin production and negative regulation of various SMs, including leporin B and cyclopiazonic acid (CPA), likely via MpkB interactions in the nucleus. These data highlight the conservation of the pheromone module in Aspergillus species, signifying the importance of this pathway in regulating fungal development and secondary metabolism.     

Different effects of carbohydrate binding modules on the viscoelasticity of nanocellulose gels

Many cellulose degrading and modifying enzymes have distinct parts called carbohydrate binding modules (CBMs). The CBMs have been shown to increase the concentration of enzymes on the insoluble substrate and thereby enhance catalytic activity. It has been suggested that CBMs also have a role in disrupting or dispersing the insoluble cellulose substrate, but dispute remains and explicit evidence of such a mechanism is lacking. We produced the isolated CBMs from two major cellulases (Cel6A and Cel7A) from Trichoderma reesei as recombinant proteins in Escherichia coli. We then studied the viscoelastic properties of native unmodified cellulose nanofibrils (CNF) in combination with the highly purified CBMs to detect possible functional effects of the CBMs on the CNF. The two CBMs showed clearly different effects on the viscoelastic properties of CNF. The difference in effects is noteworthy, yet it was not possible to conclude for example disruptive effects. We discuss here the alternative explanations for viscoelastic effects on CNF caused by CBMs, including the effect of ionic cosolutes.