Tobacco (Nicotiana tobaccum) nuclear transgenics with high copy number can express NPTII driven by the chloroplast psbA promoter

A chloroplast expression vector containing the NPTII gene under the control of apsbA promoter (psbA-NPTII) was constructed, and was biolistically delivered into both suspension cells and leaf strips of tobacco (Nicotiana tabaccum). Analyses of subsequently recovered kanamycin-resistant transgenic plants indicate that the psbA-NPTII gene was not located in the chloroplast, but was in the nucleus in very high copy number. This conclusion was based upon results from: (1) Southern hybridization analyses of chloroplast and nuclear DNAs using NPTII, chloroplast-marker, and nuclear-marker probes; (2) pulse-field gel electrophoresis; and (3) kanamycin screening of sexual progenies. This study suggests that the nuclear expression of the NPTII gene may have been associated with many copies of the psbA-NPTII construction. Very high copy number in the nucleus might either allow NPTII expression from the otherwise inadequate psbA promoter, or might increase the chance of recombining with upstream tobacco regulatory sequences.     

The genetics of blackleg [Leptosphaeria maculans (Desm.) Ces. et De Not.] resistance in rapeseed (Brassica napus L.)

The genetic control of adult-plant blackleg [Leptosphaeria maculans (Desm.) Ces. et De Not.] resistance in rapeseed (Brassica napus L.) was studied in the F₂ and first-backcross populations of the cross Maluka (blackleg-resistant) x Niklas (highly susceptible). A L. maculans isolate possessing high levels of host specificity (MB2) was used in all inoculations. Resistance/susceptibility was evaluated using three separate measures of crown-canker size, i.e. the percentage of crown girdled (%G), external lesion length (E) and internal lesion area (%II). Disease severity scores for the F₂ and first-backcross populations based on E and %II gave discontinuous distributions, indicating major-gene control for these measures of resistance; but those for %G were continuous, indicating quantitative genetic control for this measure. Chi-square tests performed on the (poorly-defined) resistance classes, based on E, in the F₂ and first-backcross populations indicated the likelihood for resistance being governed by a single, incompletely dominant major gene. Although the distributions of the F₂ and first-backcross populations, based on%II, were clearly discontinuous, the observed segregation ratios for resistance and susceptibility did not fit any of the numerous Mendelian ratios which were considered. Differences in inheritance of resistance according to the assessment method and blackleg isolate used, were discussed.     

不同生境区稻田节肢动物群落相似性分析

根据不同生境区稻田节肢动物群落系统调查结果,应用组平均聚类分析法及主成分分析法,讨论节肢动物群落的相似（相异）性问题。结果表明：生境条件及管理措施的差异对群落的结构影响较为明显,不同生境区的稻田节肢动物群落,都能在一定距离取值时聚合成一类,而水稻品种对此影响较小。主成分分析结果由二维图表达已基本满足要求。结果说明大八镇生境区稻田节肢动物群落与岗列镇生境区稻田节肢动物群落差异较大,分别列于两个极端。海陵镇生境区稻田介于两者之间,而与岗列镇生境区稻田节肢动物群落重叠。与聚类分析结果有所差异。这可能与主成分分析法损失部分信息有关。     

Identification of amino acid residues involved in the binding of Huperzine A to cholinesterases.

Huperzine A, a potential agent for therapy in Alzheimer's disease and for prophylaxis of organophosphate toxicity, has recently been characterized as a reversible inhibitor of cholinesterases. To examine the specificity of this novel compound in more detail, we have examined the interaction of the 2 stereoisomers of Huperzine A with cholinesterases and site-specific mutants that detail the involvement of specific amino acid residues. Inhibition of fetal bovine serum acetylcholinesterase by (-)-Huperzine A was 35-fold more potent than (+)-Huperzine A, with KI values of 6.2 nM and 210 nM, respectively. In addition, (-)-Huperzine A was 88-fold more potent in inhibiting Torpedo acetylcholinesterase than (+)-Huperzine A, with KI values of 0.25 microM and 22 microM, respectively. Far larger KI values that did not differ between the 2 stereoisomers were observed with horse and human serum butyrylcholinesterases. Mammalian acetylcholinesterase, Torpedo acetylcholinesterase, and mammalian butyrylcholinesterase can be distinguished by the amino acid Tyr, Phe, or Ala in the 330 position, respectively. Studies with mouse acetylcholinesterase mutants, Tyr 337 (330) Phe and Tyr 337 (330) Ala yielded a difference in reactivity that closely mimicked the native enzymes. In contrast, mutation of the conserved Glu 199 residue to Gln in Torpedo acetylcholinesterase produced only a 3-fold increase in KI value for the binding of Huperzine A.(ABSTRACT TRUNCATED AT 250 WORDS)     

Big flies, small repeats: the "Thr-Gly" region of the period gene in Diptera

The region of the clock gene period (per) that encodes a repetitive tract of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran species both within and outside the Drosophilidae. All the non- Drosophilidae sequences in this region are short and present a remarkably stable picture compared to the Drosophilidae, in which the region is much larger and extremely variable, both in size and composition. The accelerated evolution in the repetitive region of the Drosophilidae appears to be mainly due to an expansion of two ancestral repeats, one encoding a Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and asparagine or threonine. In some drosophilids the expansion involves a duplication of the pentapeptide sequence, but in Drosophila pseudoobscura both the dipeptide and the pentapeptide repeats are present in larger numbers. In the nondrosophilids, however, the pentapeptide sequence is represented by one copy and the dipeptide by two copies. These observations fulfill some of the predictions of recent theoretical models that have simulated the evolution of repetitive sequences.      

低营养条件下Paclobutrazol(PP333)对黄瓜去顶幼苗直接形成花芽的影响(简报)

植物开花机理是生物学中的一个基本问题,多年来人们进行过许多的研究,积累了大量的事实,然而对开花的机理仍然还不甚清楚。因而在利用原有实验系统的同时,有必要寻找更多简单,又便于分析的实验系统。Jullien等报告离体培养的大豆子叶节能直接产生花芽。我们在建立离体培养黄瓜子叶直接单独形成雄花或雌花的实验系统的过程中,发现黄瓜幼苗去除顶芽后在子叶节处也能直接形成花芽。这一现象有可能用于深入研究各营养器官和花启动间关系等问题,定将     

水稻自然生长趋势的数学模型和动态分析

本研究以随机过程理论为基础,应用数理方法,在分期播种的基础上,提出了一个受遗传特性控制的水稻各生物学参量自然生长趋势的数学模型。并进行了重复验证,得到了不同生育时段各生物学参量的生长速度（一阶导数）和生长速度的变化率（二阶导数）,揭示了水稻生长的基本规律。并结合实测资料,通过相关分析,得到影响各生物学参量的关键气象因子,将水稻生长的研究建立在定量的基础上,有利于更加合理地采用各项高产栽培和农田管理措施。     

高效价甘薯羽状斑驳病毒抗血清的制备

用嫁接方法将甘薯羽状斑驳病毒（ＳＰＦＭＶ）接种到Ｉ．ｓｅｔｏｓａ上扩繁,以０．２ｍｏｌ／ＬｐＨ７．２ＰＢＫ缓冲液、垫层差速离心、蔗糖密度梯度离心提取纯化ＳＰＦＭＶ。纯化的ＳＰＦＭＶＯＤ２６０／２８０的比值为１．２５。将纯化的ＳＰＦＭＶ免疫家兔制备抗血清,在环状沉淀和微量沉淀试验中,用提纯病毒测定抗血清的效价均为１：４０９６;以ＳＰＦＭＶ－ＩｇＧ为第一抗体,应用Ｄｏｔ－ＥＬＩＳＡ对甘薯和Ｉ．ｓｅｌｏｓａ叶片中的ＳＰＦＭＶ分别作了测定。