Identification and fine-mapping of a major QTL conferring resistance against head smut in maize

Head smut is one of the most devastating diseases in maize, causing severe yield loss worldwide. Here we report identification and fine-mapping of a major quantitative trait locus (QTL) conferring resistance to head smut. Two inbred lines ‘Ji1037’ (donor parent, highly resistant) and ‘Huangzao4’ (recurrent parent, highly susceptible) were crossed and then backcrossed to ‘Huangzao4’ to generate BC populations. Four putative resistance QTLs were detected in the BC₁ population, in which the major one, designated as qHSR1, was mapped on bin 2.09. The anchored ESTs, IDPs, RGAs, BAC and BAC-end sequences in bin 2.09 were exploited to develop markers to saturate the qHSR1 region. The recombinants in the qHSR1 region were obtained by screening the BC₂ population and then backcrossed again to ‘Huangzao4’ to produce 59 BC_2:3 families or selfed to generate nine BC₂F₂ families. Individuals from each BC_2:3 or BC₂F₂ family were evaluated for their resistances to head smut and genotypes at qHSR1. Analysis of genotypes between the resistant and susceptible groups within the same family allows deduction of phenotype of its parental BC₂ recombinant. Based on the 68 BC₂ recombinants, the major resistance QTL, qHSR1, was delimited into an interval of ~2 Mb, flanked by the newly developed markers SSR148152 and STS661. A large-scale survey of BC_2:3 and BC₂F₂ progeny indicated that qHSR1 could exert its genetic effect by reducing the disease incidence by ~25%. Yongsheng Chen, Qing Chao and Guoqing Tan contributed equally to this work.     

Cre/lox system and PCR-based genome engineering in Bacillus subtilis

We have developed a fast and accurate method to engineer the Bacillus subtilis genome that involves fusing by PCR two flanking homology regions with an antibiotic resistance gene cassette bordered by two mutant lox sites (lox71 and lox66). The resulting PCR products were used directly to transform B. subtilis, and then transient Cre recombinase expression in the transformants was used to recombine lox71 and lox66 into a double-mutant lox72 site, thereby excising the marker gene. The mutation process could also be accomplished in 2 days by using a strain containing a cre isopropyl-beta-d-thiogalactopyranoside (IPTG)-inducible expression cassette in the chromosome as the recipient or using the lox site-flanked cassette containing both the cre IPTG-inducible expression cassette and resistance marker. The in vivo recombination efficiencies of different lox pairs were compared; the lox72 site that remains in the chromosome after Cre recombination had a low affinity for Cre and did not interfere with subsequent rounds of Cre/lox mutagenesis. We used this method to inactivate a specific gene, to delete a long fragment, to realize the in-frame deletion of a target gene, to introduce a gene of interest, and to carry out multiple manipulations in the same background. Furthermore, it should also be applicable to large genome rearrangement.     

四川邛崃山系小熊猫分布

2000-2002年,对四川邛崃山系11个县(市)的小熊猫分布状况进行了调查.共完成调杏样线2332条,发现有小熊猫痕迹样线130条,分布在9个县,样线平均遇见率为5.57%,样线遇见率最高的是汶川县和崇州市;估算整个山系有小熊猫栖息地面积5107.82km2,以宝兴、汶川和天全3县的面积最大,分别占总面积的34.08%、30.65%和16.61%,这3个县占总面积的81.34%;小熊猫分布密度等级最高的区域是崇州市的四川鞍子河自然保护区.在山系内7个自然保护区中有小熊猫栖息地面积2166.84km2,占栖息地总面积的42.4%.小熊猫空间分布格局极不连续,存在许多空白区域,栖息地存在破碎化趋势,应进一步加强对邛崃山世界遗产地内小熊猫种群的保护.     

Transforming growth factor-beta1 protects against pulmonary artery endothelial cell apoptosis via ALK5

Transforming growth factor (TGF)-beta1 has been reported to cause endothelial cell apoptosis. However, conflicting data have also demonstrated that TGF-beta1 promotes endothelial cell survival. In this study, the effect of TGF-beta1 on apoptosis of cultured bovine pulmonary artery endothelial cells (PAEC) induced by multiple stimuli was investigated. TGF-beta1 protected against apoptosis of bovine PAEC induced by serum deprivation or the VEGF receptor inhibitor SU-5416, but not by UV light exposure or TNFalpha. Neither caspase-8 nor caspase-12 was activated by serum deprivation or the VEGF receptor blocker. However, blockade of VEGF receptors activated caspase-9, an effect that was abolished by TGF-beta1. Furthermore, serum deprivation and inhibition of VEGF receptors significantly decreased the protein level of Bcl-2, an effect that was also abrogated by TGF-beta1. In addition, the baseline level of Bcl-2 was enhanced by TGF-beta1 and reduced by inhibition of activin receptor-like kinase 5 (ALK5), a TGF-beta1 type I receptor. Furthermore, inhibition of ALK5 caused apoptosis of bovine PAEC. These results suggest that TGF-beta1 signaling is critical for maintenance of bovine PAEC survival. Finally, the protective effects of TGF-beta1 on bovine PAEC apoptosis and Bcl-2 reduction were abolished by ALK5 inhibition, but not by inhibition of non-SMAD signaling pathways. Also, TGF-beta1 activated SMAD2 and SMAD1/5, an effect that was abolished by ALK5 inhibition. The results of this study suggest that TGF-beta1 protects against bovine PAEC apoptosis, possibly through ALK5-mediated Bcl-2 induction and subsequent inhibition of the mitochondria-mediated intrinsic pathway of apoptosis. Understanding the mechanism by which TGF-beta1 promotes endothelial cell survival may provide a better treatment for apoptosis-dependent vascular diseases, such as emphysema.     

PPF1 may suppress plant senescence via activating TFL1 in transgenic Arabidopsis plants

Senescence, a sequence of biochemical and physiological events, constitutes the final stage of development In higher plants and is modulated by a variety of environmental factors and intemal factors. PPF1 possesses an important biological function in plant development by controlling the Ca2 storage capacity within chloroplasts. Here we show that the expression of PPF1 might play a pivotal role in negatively regulating plant senescence as revealed by the regulation of overexpression and suppression of PPF1 on plant development. Moreover, TFL1, a key regulator in the floral repression pathway, was screened out as one of the downstream targets for PPF1 in the senescence-signaling pathway. Investigation of the senescence-related phenotypes in PPF1(-) tfl1-1 and PPF1( ) tfl1-1 double mutants confirmed and further highlighted the relation of PPF1 with TFL1 in tranegenic plants. The activation of TFL1 expression by PPF1 defines an important pathway possibly essential for the negative regulation of plant senescence in transgenic Arabidopsis.     

ELISA法检测HBeAg假性结果原因分析

目的:探讨ELISA法检测HBeAg假性结果原因方法:用ELISA法检测乙肝血清标志物,对HBsAg阳性而HBeAg阴性的标本以及HBeAg阳性的标本用ELISA法和电化学发光法复查。结果:136例HBsAg阳性而HBeAg阴性的标本经稀释复查后检出10例HBeAg阳性标本。23例溶血标本引起HBeAg假阳性。结论:钩状效应和标本溶血是引起HBeAg假阴性和假阳性的重要原因。必要时应加以复查,以减少HBeAg的错检和漏检。     

AiiA蛋白的可溶性表达及其抗菌活性研究

AHLs是革兰氏阴性细菌在增殖过程中产生的一类信号分子,与其致病性密切相关。AiiA蛋白作为一种胞内解酯酶．能水解致病菌产生的AHb分子,使内酯环开环后不能再激活某些胞外酶的表达．从而极大地减弱了细菌的致病性。本研究从苏云金芽孢杆菌LLB15中分离编码aiiA基因的质粒DNA。用PCR方法克隆面讲基因,并利用pET载体构建6-His融合表达质粒pET29a-aiiA,转化E.coli BL21（DE3）菌株,并筛选得到E.coli BL21（DE3）-pET29a-aiiA工程菌。在20℃的低温和0．8mmol／LIPTG条件下。经25h的诱导表达,获得了54．4ug／mL可溶性AiiA蛋白。通过镍柱亲和层析,在国内外首次纯化了带6-His标记的AiiA蛋白。水解活性和抗病性检测表明,该蛋白能水解AHLs分子．对胡萝卜欧文氏软腐病菌具有较强的抗病作用。     

白芨中萜类化合物通过诱导血管内皮细胞凋亡抑制血管生成

本文研究了白芨中的萜类化合物对血管生成的抑制作用．及其抑制血管生成的可能机制。采用萃取和色谱法从白芨中分离和纯化了该萜类化合物。通过鸡胚绒毛囊膜（CAM）和人脐静脉内皮细胞（HUVEC）研究了白芨中萜类化合物及其粗提物对血管及血管内皮细胞的抑制作用。结果表明,含该萜类的粗提物显著抑制鸡胚绒毛尿囊膜血管生成;该萜类纯品能明显抑制HUVEC增殖,且可诱导HUVEC凋亡,包括细胞体积缩小,细胞膜起泡,细胞核裂解,染色质浓缩和边集,出现凋亡小体,DNA降解。因此．白芨萜类化合物的抗血管生成作用与诱导血管内皮细胞凋亡有关。     

锌离子存在下EGCG对前列腺癌细胞生长的影响

本文研究了锌离子存在下EGCG对前列腺癌细胞PC-3生长的影响．研究发现Zn^2＋可以增强EGCG抗癌活性,Zn^2＋存在下。EGCG处理后前列腺癌细胞PC-3克隆形成率显著下降。以RT—PCR、免疫组化方法研究Zn^2＋、EGCG对67kD层粘连蛋白受体（67kD Laminin Receptor,67LR）表达调控,结果表明Znn可通过上调67LR的表达,为EGCG提供更多作用的靶位点,增强EGCG对前列腺癌细胞PC-3的毒性作用。MMP-9是肿瘤侵袭转移过程中关键的基质金属蛋白酶。MMP-9活性与癌细胞的转移潜能密切相关。本文研究发现Zn^2＋、EGCG处理可通过抑制MMP-9活性,降低前列腺癌细胞PC-3的迁移率．其中80umol／LEGCG＋80umol／L Zn^2＋处理24h后显著抑制了PC-3细胞的迁移率。