L-色氨酸的研究

详细介绍了L-色氨酸的理化性质及其在食品、医药、饲料等方面的用途。列举了采用微生物转化法、酶法、直接发酵法生产L-色氨酸的工业化生产方法,为工业生产L-色氨酸提供一定依据。     

L-色氨酸5L罐发酵条件的研究

在摇瓶发酵实验的基础上,对L-色氨酸生产菌TQ2223的5L罐发酵条件进行了优化。在最优的条件下,L-色氨酸的产量达到10.3g/L。     

L-色氨酸分批发酵条件的优化

采用正交设计对L-色氨酸生产菌TQ2223的发酵培养基进行配比优化,同时对发酵温度、通风条件等进行研究,确定了该菌株的最佳分批发酵条件。     

草甘膦生物抗性和生物降解及其转基因研究

草甘膦(N—phosphonomethyl—glycine，glyphosate)毒性作用机理是竞争性抑制莽草酸途径中的5-烯醇丙酮莽草酸-3-磷酸合成酶(5-enolpyruvyl—shikimate—3—phosphate synthase，简称EPSP合成酶)的活性。EPSP合成酶是植物和微生物体内芳香族氨基酸(包括色氨酸、酪氨酸、苯丙氨酸等)生物合成过程中的一个关键酶。该酶由aroA基因编码。抗草甘膦微生物或植物中EPSP合成酶基因的核苷酸序列在相同或相近位点发生了突变。将编码EPSP合成酶的突变基因导入大豆和烟草等作物中，均能获得转基因的抗草甘膦作物。草甘膦的生物降解途径主要有两条，C-N断裂生成氨甲基磷酸(AMPA)或C-P键断裂生成肌氨酸(sarcosine)，然后两种中间代谢物进一步代谢为磷酸、甘氨酸和二氧化碳等。     

査尔酮合成酶基因及其分子进化研究进展

查尔酮合成酶基因在植物苯丙氨酸代谢途径中的作用至关重要,直接或间接影响着植物代谢产物合成、抗性调节、花色形成等生理生化过程。为了进一步加强对查尔酮合成酶基因功能的发掘与利用,本文综合归纳了査尔酮合成酶基因及其克隆、遗传多样性和分子进化等方面研究进展,得出查尔酮合成酶基因克隆采用的主要方法,进而指出査尔酮合成酶基因分异进化研究的未来方向,同时为特色基因资源开发方面研究提供技术资料检索帮助和研究方法参考。     

草铵膦对棉花根系发育影响及其生理机制

草铵膦（Phosphinothricin,PPT）在生产上使用后易在土壤中残留,但其对根系生长发育的影响国内尚无报道。本研究在温室内水培条件下用不同浓度PPT处理棉花幼苗根系,研究PPT对棉花根系发育的影响及其生理机制。结果表明,当PPT浓度为1 mg?L-1时,植株根系的总长度、面积和体积显著减小,随着PPT浓度的上升,棉花根系的总表面积、根长和体积的受抑制程度增大,当处理浓度大于5 mg?L-1时,根系的总表面积、根长和体积的受抑制程度达到最大。随着PPT处理浓度的增加,谷氨酰胺合成酶（glutamine synthetase,GS）的活力也显著下降,从而导致铵积累,这可能是草铵膦抑制根系的生长的重要原因。     

草铵膦中国专利数据统计分析

正草铵膦(glufosinate)是一种具有部分内吸作用的高效、低毒、非选择性有机磷类灭生性除草剂,是一种谷氨酰胺合成酶(GS)抑制剂,其具有L-和D-两种对映异构体,但只有L-构型具有除草活性。草铵膦是转基因抗性作物的理想除草剂,草铵膦的需求量将随着抗草铵膦转基因作物的推广种植而大大增加,其前景广阔。由于国内2012年发布的1745号公告规定,2016年7月1日停止百草枯水剂的销售和使用,使得在百草枯替代剂     

植物蔗糖合成酶功能与分子生物学研究进展

蔗糖合成酶在植物生长发育过程中有着举足轻重的作用。叶片光合产物向“库”器官运输的主要形态是蔗糖,而蔗糖合成酶是蔗糖进入各种代谢途径所必需的关键酶之一。在此,综述了蔗糖合成酶(SuSy)在高等植物蔗糖代谢中的作用,SuSy基因的克隆、表达调控机理以及SuSy转基因植株的表现;并进一步对蔗糖合成酶的研究作出设想。     

FAST指数在复原乳区分中的应用初探

FAST 指数是评价牛奶热损害的敏感指标,在研究生鲜乳热加工、奶粉及其复原乳色氨酸或梅拉德反应产物荧光强度的变化规律的基础上,评价了FAST指数用于鉴定生鲜乳和巴氏杀菌乳是否添加复原乳的效果。研究结果表明,奶粉生产过程中,色氨酸已经受到破坏,同时,不同奶粉之间色氨酸的荧光强度存在差异。与生鲜乳相比,复原乳中色氨酸荧光强度(FTrp)明显降低,随着生鲜乳中复原乳含量的增加,色氨酸的相对荧光强度线性下降;生鲜乳加热后,其中梅拉德反应产物的荧光强度(FAMP)明显升高,此类物质荧光强度升高也与牛奶中复原乳含量增加呈显著的线性相关;试验结果还表明FAST指数能有效的用于区分生鲜乳和巴氏杀菌乳,以及巴氏杀菌乳中是否添加了复原乳。     

莫把草甘膦误当草铵膦

<正>草甘膦在使用多年后,目前市场上又出现了一种新型除草剂草铵膦。在乡下经常听到农友们询问,它们仅一字之差,是不是同一类除草剂,使用中有何差异?为了解答这一问题,可以从以下几个方面将它们区分开来。从作用方式上区分草甘膦为内吸传导型广谱灭生性除草剂,主要通过抑制杂草体内烯醇丙酮基莽草素磷酸合成酶,抑制莽草素向苯丙氨酸、络氨酸和色氨酸的转化,使蛋白质的合成受到干扰,导致杂草植物死亡。草甘膦内     

Tryptophan synthesis block-associated sugar response, a physiological marker for rapid selection of Arabidopsis thaliana transformants, marked with feedback-inhibition-insensitive anthranilate synthase gene

The feedback-insensitive anthranilate synthase (AS) gene was used as a selection marker for transformants of Arabidopsis thaliana . The mutant gene ( mAS1-2 ) was constructed by substituting nucleotide at the effector-binding site of the intrinsic AS gene via PCR-mediated site-directed mutagenesis and flanked with the myrosinase promoter pyk10 to drive its expression during initial root elongation. This inducible gene cassette was first introduced into Agrobacterium tumefaciens and then delivered into A. thaliana by floral-dip inoculation. 5-methyltryptophan (5-MT) inhibited AS and suppressed seedling growth of wild type plants as a result of tryptophan starvation. With the addition of sucrose (10 mg/ml), 5-MT inhibited cotyledon opening and caused anthocyanin to accumulate in juvenile seedlings. The present mutant reversed the tryptophan starvation caused by 5-MT and blocked subsequent sugar responses. The sugar responses were detected in non-transformed plants grown on a selection medium containing 10 mg/ml of sucrose and 10 μg/ml of 5-MT after 3 days of incubation. Thus, true transformants could be selected after a short incubation, compared to the conventional kanamycin-selection method that did not eliminate all non-transformed plants.     

玉米SSⅡb蛋白多克隆抗体的制备及其应用

抗体是蛋白质功能研究的重要试剂。玉米蛋白的功能研究因缺乏相应的抗体而难以开展。玉米淀粉合酶Ⅱb与淀粉合酶Ⅱa均属于淀粉合酶,其主要负责支链淀粉的延伸。但对淀粉合酶Ⅱb的报道较少,本研究以原核表达的淀粉合酶Ⅱb的C端(455～704 aa) GST融合蛋白为抗原,免疫新西兰大白兔,分离血清制备SSⅡb多克隆抗体。Western blot试验发现, SSⅡb多克隆抗体不但能识别SSⅡb-C (455～704 aa)抗原,而且能识别玉米不同发育阶段胚乳中SSⅡb蛋白。利用该多克隆抗体的Western blot试验表明,玉米SSⅡb蛋白的表达在授粉后10 d到30 d的胚乳中表达模式是先增后降,授粉后15 d表达量最高,而半定量RT-PCR的结果表明授粉后20 d SSⅡb的转录水平最高。这些结果表明成功制备了特异的玉米SSⅡb的多克隆抗体,并能在Western blot中特异识别玉米内源SSⅡb蛋白,为进一步深入研究SSⅡb蛋白功能奠定基础。     

次生壁加厚过程中影响棉纤维素合成的 主要生理机制

笔者结合国内外对于棉纤维发育过程中纤维细胞内部生理生化反应的最新研究成果,依据棉花纤维比强度形成机制,综述了棉纤维比强度形成的关键时期次生壁加厚期,纤维素生物合成的物质变化、参与调控其合成的酶系（纤维素合成酶,蔗糖合成酶,β-1,3-葡聚糖合酶,β-1,3-葡聚糖酶,吲哚乙酸氧化酶和过氧化物酶）及影响合成的主要因素（基因型,温度,激素）等方面的研究进展。为探索改善棉纤维比强度的生理调控途径和培育高纤维强度的棉花品种提供了理论依据。     

Independent selection for seed free tryptophan content and vernalization response in chickpea domestication

Chickpea shows a distinct domestication trajectory vis‐a‐vis pod dehiscence and growth cycle mediated by vernalization insensitivity compared with its companion Near Eastern legumes. Our objectives were: (i) to map the quantitative trait loci (QTLs) associated with vernalization response and seed free tryptophan in domesticated × wild chickpea progeny and (ii) estimate the genetic correlation between vernalization response and free tryptophan content. A domesticated × wild chickpea cross was used to document phenotypic segregation in both traits and to construct a skeletal genetic map for QTL detection. A number of vernalization response and seed free tryptophan content QTLs were documented in both F₂ and F₃ generations. No significant genetic correlation between these two traits was observed. Epistatic relationship between two free tryptophan loci was documented. It is evident that selection for high seed tryptophan is easier to accomplish relative to selection for vernalization insensitivity. This suggests that the two traits were selected independently in antiquity, thereby corroborating earlier claims for conscious selection processes associated with chickpea domestication.     

Physiology of Drought Tolerance in Wheat (Triticum aestivum L.)

Correlation between lysine, tryptophan and prolamine contents during maturation of the maize kernel
Changes in the contents of total nitrogen, prolamine, tryptophan and protein bound lysine, and the relative nutritive quality of proteins were studied during the maturation of three normal maize varieties, grown under the same topographical and agrotechnical conditions, in two successive crop years.
Total nitrogen was determined according to Kjeldahl's method, prolamine by the turbidity test, lysine by Carpenter's method and tryptophan was assessed fluorometrically.
A significant decrease (p = 0.01) in total nitrogen, tryptophan and bound lysine content in the dry grain matter was found in the late milk and early dough ripeness stages of the maize kernel. Parallel with the decrease in these components, the relative nutritive quality of proteins also decreased during maturation. Prolamine, which was present in the early milk stage in low quantities, increased significantly (p = 0.01) with kernel maturity, reaching the highest level in the early dough ripeness stage. During further kernel maturation no significant changes in the components studied were observed. The correlation coefficients between the contents of prolamine and total nitrogen, lysine and tryptophan, during the ripening of maize kernel were highly significant (p = 0.001): -0.891, -0.938, -0.856, respectively in the first crop year and –0.844, -0.833, -0.867, respectively in the second crop year.     

Seed quality differences between normal,floury-2 and opaque-2 maize inbreds

Summary 142 inbreds of maize (Zea mays L.) and their fl2 and o2 versions, have been compared for seed quality traits. On average, fl2 is superior to the normal and o2 maizes in protein and oil contents and intermediate between normal and o2 in tryptophan content and DBC value. The introduction of the two mutant alleles drastically enhances the variation of the quality traits DBC value and tryptophan content. In association with the higher protein content of the fl2 versions, this effect makes it possible to identify a group of fl2 genotypes with high protein content (14.06%) and high DBC value (65.55), tryptophan content (1.32%) and oil percentage (5.92%).Supported by the Commission of the European Communities, contracts no 437 and 438.