中国水仙NtMYB7基因的克隆及功能初步研究

为研究中国水仙类黄酮代谢调控网络,从中国水仙(Narcissus tazetta var.chinensis)中克隆得到一个R2R3-MYB基因,命名为NtMYB7(GenBank登录号:MF522208)。序列分析表明,NtMYB7基因cDNA开放阅读框(ORF)为753bp,编码250个氨基酸。氨基酸多重序列比对分析发现,NtMYB7含有R2和R3保守结构域,属于R2R3-MYB家族;系统进化树分析结果显示,NtMYB7与花青素合成抑制因子聚为一类。实时荧光定量PCR分析发现,NtMYB7基因在中国水仙不同时期花瓣和副冠以及不同器官中均有表达,且NtMYB7基因在鳞茎盘中表达量最高。瞬时表达分析发现,NtMYB7使花青素合成激活因子StMYB诱导产生的红色变浅;定量PCR分析表明,NtMYB7基因显著抑制烟草黄酮醇代谢分支FLS基因的表达,同时抑制StMYB激活的花青素和原花青素合成结构基因的表达。研究结果初步判断,NtMYB7基因是中国水仙类黄酮代谢途径的抑制因子。     

The role of the genesnrf EFG andccmFH in cytochromec biosynthesis inEscherichia coli

It has been suggested that two groups ofEscherichia coli genes, theccm genes located in the 47-min region and thenrfEFG genes in the 92-min region of the chromosome, are involved in cytochromec biosynthesis during anaerobic growth. The involvement of the products of these genes in cytochromec synthesis, assembly and secretion has now been investigated. Despite their similarity to other bacterial cytochromec assembly proteins, NrfE, F and G were found not to be required for the biosynthesis of any of thec-type cytochromes inE. coli. Furthermore, these proteins were not required for the secretion of the periplasmic cytochromes, cytochromec ₅₅₀ and cytochromec ₅₅₂, or for the correct targeting of the NapC and NrfB cytochromes to the cytoplasmic membrane. NrfE and NrfG are required for formate-dependent nitrite reduction (the Nrf pathway), which involves at least twoc-type cytochromes, cytochromec ₅₅₂ and NrfB, but NrfF is not essential for this pathway. Genes similar tonrfE, nrfF andnrfG are present in theE. coli nap-ccm locus at minute 47. CcmF is similar to NrfE, the N-terminal region of CcmH is similar to NrfF and the C-terminal portion of CcmH is similar to NrfG. In contrast to NrfF, the N-terminal, NrfF-like portion of CcmH is essential for the synthesis of allc-type cytochromes. Conversely, the NrfG-like C-terminal region of CcmH is not essential for cytochromec biosynthesis. The data are consistent with proposals from this and other laboratories that CcmF and CcmH form part of a haem lyase complex required to attach haemc to C-X-X-C-H haem-binding domains. In contrast, NrfE and NrfG are proposed to fulfill a more specialised role in the assembly of the formate-dependent nitrite reductase.     

苏云金芽胞杆菌rocE基因的转录调控

【目的】rocE基因编码精氨酸降解途径中的精氨酸通透酶,通过分析苏云金芽胞杆菌(Bacillus thuringiensis,Bt) rocE基因的转录活性,明确rocE基因的转录调控机制。【方法】通过RT-PCR确定rocE基因所在基因簇的转录单元;β-半乳糖苷酶活性测定分析rocE基因启动子(ProcE)的转录活性;采用同源重组技术敲除BtHD73菌株的rocE基因;通过融合His标签的方法在大肠杆菌中表达纯化RocR蛋白的HTH结构域;通过凝胶阻滞实验明确RocR与rocE基因启动子的结合作用。【结果】在M9培养基中,精氨酸可诱导ProcE的转录活性;在SSM培养基和精氨酸诱导培养基中,与出发菌株HD73相比,ProcE在sigL (编码Sigma54因子)突变体和rocR突变体中的转录活性显著下降。RocR-HTH蛋白与ProcE有结合作用。rocE基因的缺失对菌体生长和Cry1Ac蛋白产量无显著影响。rocE缺失突变体的芽胞形成率为65.5%,HD73出发菌株为85.7%,显著性分析结果表明差异显著(P0.05)。【结论】rocE基因的转录活性受Sigma54的控制,并受RocR正调控。rocE基因的缺失影响菌株的芽胞形成率。     

Gravimetricvs. respirometric determination of metabolic efficiency in caterpillars ofPieris brassicae

Conventional gravimetry and a combination of gravimetry and respirometry were compared for their precision in measuring respiration and metabolic efficiency of growth of final stadiumPieris brassicae L. (Pieridae, Lepidoptera) caterpillars. This was done both for caterpillars feeding on an artificial diet and for caterpillars feeding on excised leaf material of a host plant,Brassica oleracea L. Gravimetry produced significantly greater variation in the total amount of matter respired and the metabolic efficiency than indirect calorimetry for caterpillars feeding on plant material, while the two methods gave similar results for the caterpillars reared on a meridic artificial diet. Respirometry (indirect calorimetry) revealed that caterpillars feeding on the artificial diet were growing with a higher metabolic efficiency than caterpillars feeding on the host plant. This difference was not revealed by conventional gravimetry. It is argued that metabolic efficiencies as derived from gravimetric budget calculations are subject to a number of random errors that distort precise determination of metabolic efficiencies in studies involving plant food.     

Presence of Rhizobium Etli bv . Phaseoli and Rhizobium Gallicum bv . Gallicum in Egyptian Soils

Seven bean rhizobial strains EBRI 2, 3, 21, 24, 26, 27 and 29 identified as Rhizobium etli, and EBRI 32 identified as Rhizobium gallicum, isolated from Egyptian soils and which nodulated Phaseolus vulgaris efficiently, were subjected to hybridization with a nifH probe in order to estimate the copy number of this gene. Seven strains (EBRI 2, 3, 21, 24, 26, 27 and 29) which were only able to nodulate Phaseolus vulgaris, contained three copies of the nifH gene, consistent with their identification as Rhizobium etli bv. phaseoli. Only one strain (EBRI 32) which nodulated both Phaseolus vulgaris and Leucaena leucocephala, had one copy of nifH gene. This confirmed the classification of this strain as Rhizobium gallicum bv. gallicum.     

Metabolic impact of redox cofactor perturbations in Saccharomyces cerevisiae

Redox cofactors play a pivotal role in coupling catabolism with anabolism and energy generation during metabolism. There exists a delicate balance in the intracellular level of these cofactors to ascertain an optimal metabolic output. Therefore, cofactors are emerging to be attractive targets to induce widespread changes in metabolism. We present a detailed analysis of the impact of perturbations in redox cofactors in the cytosol or mitochondria on glucose and energy metabolism in Saccharomyces cerevisiae to aid metabolic engineering decisions that involve cofactor engineering. We enhanced NADH oxidation by introducing NADH oxidase or alternative oxidase, its ATP-mediated conversion to NADPH using NADH kinase as well as the interconversion of NADH and NADPH independent of ATP by the soluble, non-proton-translocating bacterial transhydrogenase. Decreasing cytosolic NADH level lowered glycerol production, while decreasing mitochondrial NADH lowered ethanol production. However, when these reactions were coupled with NADPH production, the metabolic changes were more moderated. The direct consequence of these perturbations could be seen in the shift of the intracellular concentrations of the cofactors. The changes in product profile and intracellular metabolite levels were closely linked to the ATP requirement for biomass synthesis and the efficiency of oxidative phosphorylation, as estimated from a simple stoichiometric model. The results presented here will provide valuable insights for a quantitative understanding and prediction of cellular response to redox-based perturbations for metabolic engineering applications.     

应恢复赤车属头序赤车组和头序赤车

头序赤车的特征在于其具花序托和总苞的雌头状花序,根据此一特征即可将它与赤车属的其它所有种区别开。因此,在2002年被错误归并为异名的此赤车属进化种,以及根据其建立的单种进化组头序赤车组在该文中予以恢复。     

敲除aceE基因对猪链球菌丙酮酸代谢的影响

【目的】探究缺失编码丙酮酸脱氢酶蛋白的aceE基因对猪链球菌生长特性、三羧酸循环和丙酮酸代谢的影响。【方法】通过测量菌液的OD600值,绘制野生型菌株与aceE基因缺失突变株的生长曲线;利用试剂盒测定三羧酸循环和丙酮酸代谢旁路中乙酰CoA、琥珀酸CoA、延胡索酸、草酰乙酸、丙酮酸、乳酸和ATP的含量,通过荧光定量qRT-PCR确定柠檬酸合酶基因、苹果酸脱氢酶基因、琥珀酸脱氢酶基因、异柠檬酸脱氢酶基因、丙酮酸脱羧酶基因、乳酸脱氢酶基因、乙醇脱氢酶基因和乙醛脱氢酶基因的表达水平。【结果】与野生株相比,菌株ΔaceE在平台期OD600值下降;添加1g/L乙酸盐能够显著提升菌株ΔaceE平台期OD600值。菌株ΔaceE的丙酮酸含量上升,ATP含量下降;三羧酸循环代谢中乙酰CoA、琥珀酸CoA、延胡索酸含量降低;柠檬酸合酶基因和苹果酸脱氢酶基因表达水平上升,琥珀酸脱氢酶基因和异柠檬酸脱氢酶基因表达水平下调;在丙酮酸代谢旁路中丙酮酸脱羧酶基因、乳酸脱氢酶基因、乙醇脱氢酶基因和乙醛脱氢酶基因表达水平上升。【结论】结果显示,菌株ΔaceE三羧酸循环活性降低,虽然能够通过PDH旁路将部分丙酮酸分解为乙...     

中国黑粉菌属和利罗黑粉菌属

黑粉菌属是Roussel 1806年建立的,全世界记载有三百余种,主要寄生于禾本科,是经济作物及牧草的重要致病菌·长期以来,对黑粉菌的邢子使用过各种名称,如厚垣孢子,冬孢子及黑粉孢子等.本文采用黑粉孢子以区别锈菌的冬孢子. 芳’(1979)在《中国真菌总汇》中列出黑粉菌属五十种及一个变型.作者经过显微结构和超显微结构的研究,承认其中二十九种为正确名称,八种及一变型为异名,顶黑粉菌(Ustilago acrearus Berk.)由于错拼而被废弃.埃地黑粉菌(Ustilago emodensis Berk.)被转移至利罗粉菌属(Liroa).另有十一种黑粉菌因缺少标本留待今后订正.自1979年以后,杨信东(1983)增加黑粉菌属二种我国新纪录,K.范基和郭林(1986)描述一新种,四种新纪录.在本文中,作者描述一新种:鸢尾蒜黑粉(Ustilago ixiolirii Guo L) ,孢子堆生在蒴果内,不开裂,黑色,粉末状.黑粉孢子球形,近球形,稀椭圆形, 12.5-21×10-21μm,黑褐色,壁厚1-1.Sμm,纹饰脑状.是迄今生在石蒜科植物上唯一黑粉菌的种,其它几种黑粉菌均属条黑粉菌属.本文增加七种我国新纪录.共计四十九种,寄生于六科四十四属植物,主要是禾本科和蓼科.这仅是黑粉菌属研究的初步报告,在全国范围内大量采集黑粉菌标本后,作者相信会有更多新种和我国新纪录被发现.利罗黑粉菌属(Liroa)是从黑粉菌属(Ustaligo)分出的,此属为单种属.     

A previously unrecognized glutamine synthetase expressed in Klebsiella pneumoniae from the glnT locus of Rhizobium leguminosarum

Summary Using glnT DNA of Rhizobium meliloti as a hybridization probe we identified a R. leguminosarum biovar phaseoli (R. l. phaseoli) locus (glnT) expressing a glutamine synthetase activity in Klebsiella pneumoniae. A 2.2 kb DNA fragment from R. l. phaseoli was cloned to give plasmid pMW5a, which shows interspecific complementation of a K. pneumoniae glnA mutant. The cloned sequence did not show cross-hybridization to glnA or glnII, the genes coding for two glutamine synthetase isozymes of Rhizobium spp. While in previous reports on glnT of R. meliloti and Agrobacterium tumefaciens no glutamine synthetase activity was detected, we do find activity with the glnT locus of R. l. phaseoli. The glutamine synthetase (GSIII) activity expressed in a K. pneumoniae glnA strain from pMW5a shows a ratio of biosynthetic to transferase activity 10³-fold higher than that observed for GSI or GSII. GSIII is similar in molecular weight and heat stability to GSI.     

In vitro testing of anthelmintic efficacy of Flemingia vestita (Fabaceae) on carbohydrate metabolism in Rallietina echinobothrida

The root tuber peel of Flemingia vestita has been in use in local traditional medicine against intestinal worm infections in Meghalaya (North-East India). In order to evaluate and authenticate the anthelminitc efficacy of the isoflavones of F. vestita, the root peel extract of this putative plant was tested against several helminth parasites, extensively on Rallietina echinobothrida, with respect to different parameters of these parasites. In this paper, we describe various methods to evaluate the anthelmintic efficacy of this medicinal plant with respect to carbohydrate metabolism in R. echinobothrida at paralytic time caused by the isoflavones of F. vestita. To meet the high energy demand by the parasite due to the anthelmintic stress, glucose breakdown follows the PEPCK-malate pathway in the parasite.     

Mutations affecting regulation of the anabolic argF and the catabolic aru genes in Pseudomonas aeruginosa PAO

Summary The nucleotide sequence required for a fully functional promoter and operator of the Pseudomonas aeruginosa argF gene (argF _po), the arginine-repressible gene for anabolic ornithine carbamoyltransferase, was defined within a 160 by region. The streptomycin (Sm) resistance genes strAB of plasmid RSF1010 were fused to argF _po. This construct in P. aeruginosa strain PAO conferred resistance to Sm. Mutants of strain PAO were selected which were resistant to Sm in the presence of arginine due to constitutive expression of argF _po —strAB. These mutants were designated argR. They were unable to grow or grew poorly on arginine or ornithine as the sole carbon and nitrogen source. This growth defect (Aru^–/Oru^– phenotype) was correlated with a reduced level of N-succinylornithine aminotransferase, an enzyme participating in the major aerobic pathway for arginine and ornithine catabolism in this organism. The argR mutants were classified into four groups by transduction analysis and three argR mutations were mapped on the PAO chromosome. argR9901 and argR9902 were co-transducible with car-9 (at 1 min) and thus close to the oru-310 locus; argR9906 was localized in the oruI (=aru) gene cluster (67 min). Some aru mutants, which have been isolated previously and which produce very low amounts of all enzymes in the arginine succinyltransferase pathway, were unable to repress the argF gene in an arginine medium. Thus, P. aeruginosa PAO appears to have multiple genes that are involved in the regulation of both the anabolic argF and the catabolic aru genes.Abbreviations Arg^– arginine auxotrophy - Aru arginine utilization - Oru ornithine utilization     

八棱海棠种子超低温保存中含水量对糖代谢的影响

含水量是影响种子超低温保存效果的关键因素，而其作用机制尚不完全清楚。为探讨含水量对种子超低温保存生活力的影响途径，该研究以八棱海棠种子为材料，通过硅胶干燥法获得不同含水量的种子，测定超低温保存后种子生活力、糖含量及相关酶指标的变化并分析相关性。结果表明：(1)超低温保存15 d后，不同含水量种子生活力不同，随着种子含水量的降低，种子生活力呈现先升高后降低的趋势，含水量为9.02%的八棱海棠种子生活力最高，为53.33%;超低温保存120 d后，种子生活力随着含水量下降一直升高，含水量为6.40%生活力最高，为27.78%。这表明八棱海棠种子含水量对超低温保存后的生活力有明显影响，但受液氮保存时间影响，随着液氮保存时间的延长，最适含水量降低。(2)相关分析显示，超低温保存后种子含水量与生活力呈极显著负相关(r=-0.82);与果糖和蔗糖含量、酸性转化酶、果糖激酶呈显著负相关，而种子萌发率与这些指标呈显著正相关。这表明种子含水量通过影响酸性转化酶活性而影响蔗糖和果糖含量，进而影响蔗糖代谢，响应低温和脱水胁迫，最终导致生活力差异。种子生活力还受到介导果糖激酶的果糖代谢影响。此外，海藻糖也是种...     

福贡银莲花(毛茛科)与光叶银莲花属于同一分类实体

通过标本检查,发现福贡银莲花(Anemone yulongshanica W.T.Wang var.glabrescens W.T.Wang)(毛茛科)与光叶银莲花(A.obtusiloba D.Don ssp.leiophylla W.T.Wang)没有本质区别,应属于同一分类实体,故将前者处理为后者的异名。     

Quantitative analysis of a stand of Pinus densiflora undergoing succession to Quercus mongolica ssp. crispula : II. Growth and population dynamics of Q. mongolica ssp. crispula under the P. densiflora canopy

We report here the results of an 8-year study of the growth and population dynamics of Quercus mongolica ssp. crispula in a Pinus densiflora stand in a state of succession. In 1998, there were 169 Q. mongolica ssp. crispula individuals in a 400-m² plot under the P. densiflora canopy. This number remained nearly constant between 1998 and 2005. Mean recruitment of new individuals was 11 year⁻¹, while mean mortality was 12 year⁻¹. Of the 35 individuals ≥60 cm in height existing in 1998, 30 were still surviving in 2005. We were able to represent the height growth of Q. mongolica ssp. crispula individuals as H=30 [1+21.96 exp(−0.0839t)]⁻¹, with t = years since 1998 and H = height in meters. Using this equation we predict that by 2015 the mean height of Q. mongolica ssp. crispula trees in the stand will exceed those of understory trees, such as Rhus trichocarpa and Prunus maximowiczii. Once above the understory stratum, the Q. mongolica ssp. crispula trees can be expected to grow more rapidly due to the better light conditions, thereby rapidly reaching the canopy stratum of the P. densiflora stand.     

核桃细菌性黑斑病菌rpfG基因的功能分析

[目的] 本研究旨在揭示核桃细菌性黑斑病菌（Xanthomonas arboricola pv.juglandis,Xaj） DW3F3中rpfG基因的生物学功能,从而为核桃细菌性黑斑病防治药剂的开发提供作用靶点。[方法] 以野油菜黄单胞菌（Xanthomonas campestris pv.campestris,Xcc）8004菌株以及水稻白叶枯病菌（Xanthomonas oryzae pv.oryzae,Xoo） PXO99^A的rpfG基因为模板序列,对Xaj野生型菌株DW3F3的基因组序列进行检索。利用同源重组技术,对Xaj中rpfG基因进行敲除,并用生物化学方法对基因缺失菌株的相关毒力因子、抗逆性进行检测。[结果] 通过同源比对,在XajDW3F3的基因组中发现了与XccrpfG、XoorpfG同源的基因,并成功获得rpfG的缺失突变株ΔrpfG。与野生型相比,突变株ΔrpfG的生物被膜形成能力仅为野生型XajDW3F3的44.58%;胞外多糖产量也由野生型的8.47 mg/mL降为5.23 mg/mL;ΔrpfG的絮凝活性增加,能使菌液变澄清;运动性实验显示ΔrpfG的运动直径比野生型增加了12.38%;胞外酶的分泌也发生了不同程度的改变,突变株分泌纤维素酶的能力极显著降低,淀粉酶活性有所提高,而分泌蛋白酶的能力未发生变化;此外rpfG缺失后,Xaj对逆境（盐、酸、SDS、硫酸铜）的耐受力降低。[结论] 结果表明rpfG基因能影响核桃细菌性黑斑病菌的致病相关性状,并赋予了细菌一定的抗逆性。