野油菜黄单胞菌重组克隆pIXU9278对黄原胶生物合成的影响

用ＰＩＪ３２００作为载体,构建了包含１５６２个重组克隆野生型野油菜黄单胞菌的粘粒文库,通过三亲交配法,基因文库中的重组克隆可以在ＰＲＫ２０１３的帮助下,从Ｅ．ｃｏｄｉ中以ＸＣＣＮＡＵ－９２中,绝大多数重线克隆对黄原胶合成无影响,但导致菌株生长缓慢,工程菌株ＸＣＣＮＡＵ－９２７８（ＰＩＸＵ９２７８）在２８℃、１２０ｔ／ｍｉｎ条件下发酵７２ｈ,产量达３７．５０ｇ／ｋｇ,发酵液度力为１４６００ｍＰａ．ｓ     

白茶萎凋过程中儿茶素合成关键酶基因表达分析

[目的]研究白茶萎凋过程中茶多酚、儿茶素组分含量变化与其合成途径中关键酶基因的动态表达,为优化白茶的萎凋工艺提供参考依据.[方法]以不同萎凋阶段的白茶为原料,分别采用福林酚(Folin-Ciocalten)比色法和高效液相色谱法(HPLC)测定茶多酚、儿茶素组分含量的变化,并以实时荧光定量PCR检测白茶萎凋过程中与儿茶素物质代谢合成相关基因(PAL、C4H、CHS、CHI、F3'5'H、FYH、F3H、DFR、LAR、ANS、ANR和UGGT)的相对表达量.[结果]白茶萎凋过程中茶多酚含量呈逐渐降低趋势,儿茶素组分中表儿茶素(EC)、没食子儿茶素(GC)、表没食子儿茶素(EGC)、表儿茶素没食子酸酯(ECG)含量整体上呈先上升后下降的变化趋势,且均在萎凋历时32h出现最大值.实时荧光定量PCR检测结果表明,儿茶素生物合成途径关键酶基因PAL、C4H、CHI、F3H、F3'H、F35'H、DFR、LAR、ANR和UGG丁均在萎凋历时32 b呈上调表达,CH基因则随萎凋历时的增加呈下调表达趋势,ANS基因表达在整个萎凋过程中呈先上升后下降的变化趋势,在萎凋历时16 h达最大值.白茶萎凋过程中儿茶素合成途径关键基因表达水平具有调控儿茶素生物合成的作用.[结论]在白茶萎凋过程中,儿茶素生物合成途径关键酶基因PAL、C4H、F3H、FYH、DFR、LAR、ANR的表达与儿茶素组分单体EC、GC、EGC的积累规律基本一致,其最大值均出现在萎凋历时32 h,因此在制茶时可适当缩短萎凋时长,以提高白茶品质.     

Recent developments in auxin biology and new opportunities for auxinic herbicide research

Auxinic herbicides mimic the effects of natural auxin. However, in spite of decades of research, the site(s) of action of auxinic herbicides has remained unknown and many physiological aspects of their function are unclear. Recent advances in auxin biology provide new opportunities for research into the mode of action of auxinic herbicides. Of considerable interest is the discovery of auxin receptors (TIR1 and possibly ABP1) that may lead to the discovery of auxinic herbicide site(s) of action. Knowledge of auxin-conjugating enzymes and auxin signal transduction components may shed new light on herbicide activity, selectivity in dicots, and mechanisms leading to phytotoxicity in sensitive plants. Analysis of genes induced in response to auxin may provide a novel approach for detection of off-target herbicide injury in crops. For example, the auxin-responsive gene GH3 is highly and specifically induced in response to auxinic herbicides in soybean, and may offer a novel method for diagnosing auxinic herbicide injury. Advances in our understanding of auxin biology will provide many new avenues and opportunities for auxinic herbicide research in the future.     

Subnormal concentrations of serum cobalamin (vitamin B12) in cats with gastrointestinal disease

The present study sought to determine the spectrum of diseases associated with subnormal concentrations of serum cobalamin in cats undergoing investigation of suspected gastrointestinal problems. The solid-phase boil radioassay (RA) for cobalamin employed in the present study was immunologically specific, precise, and accurate, with a sensitivity of 15 pg/mL. The RA yielded results that strongly correlated with those obtained by bioassay (Spearmann rho = .805; P < .0001), although the absolute values were lower for the RA. Forty-nine of 80 serum samples submitted during the period of January 1996-January 1998 had cobalamin concentrations below the reference range for healthy cats (range 900-2,800 pg/mL; mean +/- SD, 1,775 +/- 535 pg/mL; n = 33). Cats with subnormal cobalamin concentrations (mean +/- SD; 384 +/- 272 pg/mL, range 3-883 pg/mL) were middle-aged or older and were presented for weight loss. diarrhea, vomiting, anorexia, and thickened intestines. Definitive diagnoses in 22 cats included inflammatory bowel disease (IBD), intestinal lymphoma, cholangiohepatitis or cholangits, and pancreatic inflammation. Serum concentrations of cobalamin were particularly low in cats with intestinal lymphoma, three-fifths of whom also had subnormal serum concentrations of folate (< 9 ng/mL). The simultaneous presence of disease in the intestines, pancreas, or hepatobiliary system in many cats made it difficult to determine the cause of subnormal cobalamin concentrations. The circulating half-life of parenteral cyanocobalamin was shorter in 2 cats with IBD (5 days) than in 4 healthy cats (12.75 days). The presence of subnormal serum concentrations of cobalamin in 49 of 80 cats evaluated suggests that the measurement of serum cobalamin may be a useful indirect indicator of enteric or pancreatic disease in cats. The rapid depletion of circulating cobalamin in cats suggests that cats may be highly susceptible to cobalamin deficiency. However, the relationship of subnormal serum cobalamin concentrations to cobalamin deficiency and the effect of cobalamin deficiency on cats remain to be determined.     

Genetic control of resistance to tridemorph inustilago maydis

Mutants ofUstilago maydis with low resistance to tridemorph isolated in a mutation frequency of 7x 10^-6 after UV-irradiation and selection on media containing 25 μg ml^-1 tridemorph. Genetic analysis with nine such mutant isolates resulted in the identification of two unlinked chromosomal loci,U/tdm- 1 andU/tdm- 2. TheU/tdm mutations are responsible for low resistance levels to tridemorph (resistance factor, Rf, of 3 or 5 based on effective concentration causing a 50% reduction in the growth rate (EC₅₀) or minimal inhibitory concentration (MIC) values, respectively) and low to moderate level of resistance to fenpropimorph (Rf 10 or 16 based on MIC or EC₅₀, respectively) and fenpropidin (Rf 5 or 11 based on MIC or EC₅₀, respectively). Haploid strains carrying bothU/tdm mutations exhibit higher levels of resistance to the above fungicides, indicating interallelic interaction between nonallelic genes. Crosses between mutants carrying theU/tdm- genes with compatible isolates carrying theU/fpm- 1 orU/fpm- 2 mutations, which were found in previous work to carry fenpropimorph resistance, yielded in all cases a large number of recombinants with wild-type sensitivity, indicating that the mutant genes involved were not allelic. Cross-resistance studies with the inhibitors of C-14 demethylase showed that. the U/tdm-mutations were responsible for increased sensitivity to the triazoles triadimefon, triadimenol, propiconazole and flusilazole, and to the pyridine pyrifenox. Study of gene effect on the fitness ofU. maydis showed thatU/tdm-mutations appeared to be pleiotropic, having more or less adverse effects on growth rate in liquid culture and pathogenicity on young corn plants.     

光合细菌类胡萝卜素研究

阐述了类胡萝卜素在光合细菌光合作用中的重要功能以及在色素蛋白复合体中的立体空间结构和功能。详细描述了光合细菌非环状类胡萝卜素合成途径以及合成途径中重要抑制位点、类胡萝卜素生物合成酶基因及分子调控机制。对类胡萝卜素影响生物产氢进行了分析和评述。对光合细菌类胡萝卜素研究中存在的问题和发展趋势进行了讨论。     

Sensitivity Detection Technique and Resistance Risk Assessment of Magnaporthe grisea to Tricyclazole

In vitro detection method for the sensitivity of Magnaporthe grisea to tricyclazole was studied, and the potential resistance risk of blast disease to tricyclazole was assessed. Both EC5o of hyphal melanization (ECso-H) and minimum inhibitive concentration of melanization in appressorial (MIC-A) by inhibitor tricyclazole showed positive correlation to the EC5o of tricyclazole against blast disease tested in vivo, with relative co-efficiency (R2) of 0.8995 and 0.8244, respectively. However, stability and reproducibility of ECso-H were better than those of MIC-A, suggesting that it could be used to detect the sensitivity of M. grisea to tricyclazole in vitro. Tricyclazole sensitivity of the progenies derived from single spores of the most sensitive isolate DY2 and the least sensitive isolate GY6 detected in sensitivity monitoring in 2000 was not stable, with mean EC50 values of 4.4968μg/mL and 5.4010μg/mL, respectively, indicating that the difference in EC5o between DY2 and GY6 was not caused probably by resistance variation. EC5o of GY6 did not increase significantly when continuously selected for twenty generations under the selection pressure of tricyclazole in vivo. However, the sensitivity of DY2 was decreased by 10-fold after selected for twenty generations.The results suggested that tricyclazole was still low resistance risk for M. grisea in China.     

蔗糖对茶树儿茶素生物合成的影响

儿茶素是茶树重要的次生代谢产物,也是茶叶的重要功能物质,具有多种药理活性。因此正确评价茶叶及其制品中儿茶素含量,了解儿茶素生物合成及其调控手段具有重要的意义。利用香草醛盐酸比色法、HPLC等方法,研究蔗糖诱导子处理对茶儿茶素生物合成的影响,并通过qRT-PCR技术分析蔗糖处理对茶树儿茶素生物合成过程中基因表达的影响。结果显示,无论是茶树愈伤组织还是茶树幼苗经蔗糖处理后其儿茶素含量及组分都有所增加,但是高浓度的蔗糖会抑制茶树愈伤组织的生长,特别是在液体培养的早期添加蔗糖。添加适当浓度的蔗糖能增加茶树愈伤组织中非酯型儿茶素C和EC的含量;蔗糖处理后茶树幼苗中非酯型儿茶素EGC和EC含量明显上升,而酯型儿茶素 EGCG相对含量有所下降。qRT-PCR分析显示蔗糖诱导了茶树幼苗中C4H、CHS、CHI、F3H、LAR、ANR、DFR、F3’H、F3’5’H基因表达,其中变化最明显的是F3H,其次是ANR、CHS。这进一步证实了F3H、ANR为茶树儿茶素合成的关键基因。