The Maize Oil Yellow1 (Oy1) Gene Encodes the I Subunit of Magnesium Chelatase

Semi-dominant Oil yellow1 (Oy1) mutants of maize (Zea mays) are deficient in the conversion of protoporphyrin IX to magnesium protoporphyrin IX, the first committed step of chlorophyll biosynthesis. Using a candidate gene approach, a cDNA clone was isolated that was predicted to encode the I subunit of magnesium chelatase (ZmCHLI) and mapped to the same genetic interval as Oy1. Allelic variation was identified at ZmCHLI between wild-type plants and plants carrying semi-dominant alleles of Oy1. These differences revealed putative amino acid substitutions that could account for the alterations in protein function. Candidate lesions were tested by introduction of homologous changes into the Synechocystis magnesium chelatase I gene (SschlI) and characterization of the activity of mutant protein variants in an in vitro enzyme activity assay. The results of these analyses suggest that SsChlI protein variants containing the substitutions identified in the dominant Oy1 maize alleles lack activity necessary for magnesium chelation and confer a semi-dominant phenotype via competitive inhibition of wild-type SsChlI.     

High Lysine and High Tryptophan Transgenic Maize Resulting from the Reduction of Both 19- and 22-kD α-zeins

The major maize seed storage proteins, zeins, are deficient in lysine and tryptophan content, which contribute to the poor nutritional quality of corn. Whether through the identification of mutations or genetic engineering, kernels with reduced levels of zein proteins have been shown to have increased levels of lysine and tryptophan. It has been hypothesized that these increases are due to the reduction of lysine-poor zeins and a pleiotropic increase in the lysine-rich non-zein proteins. By transforming maize with constructs expressing chimeric double-stranded RNA, kernels derived from stable transgenic plants displayed significant declines in the accumulation of both 19- and 22-kD α-zeins, which resulted in higher lysine and tryptophan content than previously reported for kernels with reduced zein levels. The observation that lysine and tryptophan content is correlated with the protein levels measured in transgenic maize kernels is consistent with the hypothesis that a pleiotropic increase in non-zein proteins is contributing to an improved amino acid balance. In addition, a large increase in accumulation of free amino acids, consisting predominantly of asparagine, asparate and glutamate, was observed in the zein reduction kernels.     

玉米低密度育种芯片开发及在种质资源评价中的应用

SNP基因分型芯片是分子育种的重要工具,高密度SNP芯片往往存在标记冗余、价格高、目标性不强等问题,是分子育种走向常规化、规模化的主要限制因素之一.本研究介绍了一款新开发的低密度育种芯片,并就芯片在种质资源评价中的价值进行了分析.首先,对37份玉米自交系进行10×重测序,获得了18.2 Mb的SNP标记,从中挑选208...     

强光和短期高浓度CO2对玉米和大豆光能转化效率的影响

盆栽和人工光源条件下,玉米叶片在普通空气中对强光照射不敏感,在高浓度CO2中强光照射0～5h后,光合速率(Pn)逐渐降低,无机磷(Pi)限制是其主要原因之一;大豆叶片在普通空气中受强光照射5h后,Fv／Fm、Pn、羧化效率(CE)和表观量子效率(AOY)明显降低,Fo升高,在高浓度CO2和强光下大豆Fo上升、Fv／Fm和气体交换参数下降的幅度减小。研究表明,高浓度CO2可减轻强光对植物尤其是C3植物光合功能的损伤,有限地缓解光抑制,但不能完全消除强光导致的大豆Pn和气孔导度(Gs)的降低。     

Fusarium mycotoxins in forage maize — Detection and evaluation

The deoxynivalenol concentrations found in forage maize ranged between 0.24 and 14.29 mg/kg DM (detected by ELISA). When highly contaminated samples were analysed for deoxynivalenol by HPLC or LC-MS the resulting concentrations were in the mean about 50% lower. Furthermore, using LC-MS other type-A and type-B trichothecenes, zearalenone and α-zearalenol were found in these samples. The differences between ELISA and HPLC/LC-MS data for deoxynivalenol are assumed to result from cross-reactions of other trichothecenes with the antibodies used in ELISA and toxin losses from sample purification procedures needed for HPLC and LC-MS analysis. Presented at the 26^th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004     

鲤春血症病毒中国分离株糖蛋白基因和氨基酸序列的初步解析

2002～2004年间从国内养殖鲤科鱼类和观赏鱼类中分离出8株鲤春血症病毒(SVCV)。根据SVCV参考株 全序列,设计引物,用逆转录聚合酶链式反应扩增出8株SVCV糖蛋白编码基因片段,并对扩增产物进行了克隆和 序列测定。用生物信息学方法对测得的序列进行分析,结果8个国内分离株的糖蛋白基因序列与参考株的基因序 列相似性均在92％以上,8个国内分离株之间基因序列相似性均在97．7％以上;8个国内分离株之间糖蛋白推导 出的氨基酸序列相似性均在94．5％以上,与参考株氨基酸序列相似性在92．9％-94．9％之间。系统发育树分析结 果表明,SVCV国内分离株与USA株、980451株、980528株和970469株的进化方向一致,与其它SVCV毒株在进 化方向上不同。8个毒株有19个共同的酶切位点,推导出的氨基酸序列中有10个亲水区、10个可能的抗原位点 和10个跨膜蛋白区域,其峰值基本一致。对SVCV国内分离株的糖蛋白6个功能位点(天冬酰胺糖基化位点、精 氨酸-甘氨酸-天冬氨酸序列、酪蛋白激酶Ⅱ磷酸化位点、蛋白激酶C磷酸化位点、酪氨酸磷酸化位点和肉豆蔻酰 基化位点)进行了初步分析。     

RAPD技术在黑糯玉米亲缘关系划分上的应用

以8个黑糯玉米自交系为试验材料,利用CTAB微量提取法从幼苗中提取DNA,进行RAPD扩增,筛选出3个能产生稳定遗传多态性的引物,分别是OP—A01、OP—A11和OP-006;利用这些引物的扩增出的指纹图谱,进行聚类分析,可将8个自交系划分为4个类群,与各个自交系的来源基本一致。表明RAPD可以用于黑糯玉米亲缘关系的划分。     

淹水玉米幼苗根尖分生细胞内Ca2+超微细胞化学定位

采用焦锑酸钾沉淀法,对遭受淹水胁迫的玉米幼苗初生根根尖分生细胞内钙离子分布变化情况进行了电镜细胞化学观察。在正常状态下,根尖分生细胞内Ca^2＋沉淀颗粒的分布较少．主要位于细胞核和细胞质中。在淹水1h后,根尖分生细胞内呈现有大量Ca^2＋沉淀颗粒分布,细胞核和细胞质中分布的Ca^2＋沉淀颗粒密度,远大于正常细胞。随着淹水时间的延长,根尖分生细胞的细胞核和细胞质中分布的Ca^2＋沉淀颗粒呈现不断增多的趋势,而液泡中分布的Ca^2＋沉淀颗粒则逐步明显减少。根据实验结果本文对受淹根尖分生细胞的死亡与Ca^2＋分布变化的关系进行了研究。     

Lethal and sublethal effects of the naturally derived insecticide spinosad on parasitoids of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Laboratory studies were performed on the lethal and sublethal effects of spinosad on three important species of parasitoids attacking Spodoptera frugiperda (J.E. Smith) in Mexico. Reproduction of the braconid Chelonus insularis (Cresson), on treated egg masses was completely eliminated at 200 parts per million (ppm) and reduced by ∼70% at 20 ppm compared to the controls. Adult C. insularis did not avoid contact with residues on maize (200 ppm), but suffered a 7-day reduction in longevity after contact with residues. Initial toxicity of spinosad applied to a natural host of S. frugiperda was concentration dependent and resulted in 23 to 100% mortality of the eulophid Euplectrus plathypenae Howard at 25 to 200 ppm, respectively. The survival of Eu. plathypenae was initially reduced, especially in males, following contact with field weathered residues on maize (200 ppm). However, survival of both sexes rapidly returned to control values on foliage sampled after rainfall. A similar effect was observed in the mortality response of female Eu. plathypenae exposed to residues on sorghum. The ichneumonid Eiphosoma vitticolle Cresson did not avoid reproduction in S. frugiperda larvae that were externally contaminated with 200 ppm spinosad, although all spinosad-treated hosts died before the parasitoid progeny could develop. We use these results to predict the impact of spinosad applications on the foraging and reproduction of these parasitoids in the field. Such predictions require validation by field studies.     

^60Co-γ射线辐照降解的壳聚糖对玉米萌发及生长的影响

采用不同剂量60Co-γ射线辐照降解壳聚糖,研究了其降解产物对玉米生长的调节作用.研究发现,壳聚糖辐照产物可提高玉米种子发芽率,促进玉米幼苗生长,提高玉米抗逆相关生理生化指标.辐照剂量为200 kGy,壳聚糖辐照产物溶液浓度为3.0 mg/mL时,可显著提高玉米种子萌发率和促进芽长;浓度为4.0 mg/mL时,显著促进主根长度;浓度为2.0 mg/mL～3.0 mg/mL,苯丙氨酸解氨酶 (PAL)活性显著高于对照.当辐照剂量为200 kGy～400 kGy,产物溶液浓度为2.0 mg/mL～4.0 mg/mL时,能显著提高胚乳中α-淀粉酶活性和幼苗中叶绿素含量;浓度为2.0 mg/mL～3.0 mg/mL时,显著提高幼苗过氧化物酶 (POD) 的活性.综合多种影响因素得出:利用壳聚糖辐照产物开发玉米促生抗逆剂的适宜60Co-γ射线辐照剂量为200 kGy～300 kGy,浓度为2.0 mg/mL～3.0 mg/mL.