毛乌素沙地柠条群体分子生态学 初步研究：RAPD证据

毛乌素沙地柠条群体是一个杂种带。为了进一步阐明分子变异和基因流与生境或生态过渡带的联系,应用ＲＡＰＤ标记开展了柠条群体的分子生态学研究。根据ＲＡＰＤ数据利用Ｓｈａｎｎｏｎ信息指数估计了６个柠条群体的遗传多样性,发现大部分的分子变异存在于柠条群体之内（８２．４％）,只有少部分的分子变异存在于群体之间（１７．６％）。又利用Ｎｅｉ指数统计了ＲＡＰＤ数据,也证实了大部分的遗传变异存在于群体之内。柠条锦鸡儿群体与中间锦鸡儿群体的遗传分化系数和遗传距离都很小。以上结果都肯定了柠条群体间和种间的基因流动。无论是从多态位点比率还是群体的遗传多样性来看,硬梁和硬梁覆沙群体是最小的,滩地覆沙群体则具有较高的水平。某些ＲＡＰＤ扩增片段的频率在柠条群体间有规律的变化也许具有着特殊的生态学意义,更可能是中性突变的随机固定。根据以上研究可以得出下列结论：①通过比较Ｓｈａｎｎｏｎ指数和Ｎｅｉ指数的统计结果,可以认为,对于异交植物来讲,Ｓｈａｎｎｏｎ指数在统计ＲＡＰＤ数据方面有用。②毛乌素沙地柠条群体之间存在着强大的基因流,物种的杂交性与生态过渡性一致     

A new member of the CAB gene family: structure,expression and chromosomal location of Cab-8, the tomato gene encoding the Type III chlorophyll a/b-binding polypeptide of photosystem I

We have previously reported the isolation and characterization of tomato nuclear genes encoding two types of chlorophyll a/b-binding (CAB) polypeptides localized in photosystem (PS) I and two types of CAB polypeptides localized in PSII. Sequence comparisons shows that all these genes are related to each other and thus belong to a single gene family. Here we report the isolation and characterization of an additional member of the tomato CAB gene family, the single tomato nuclear gene, designated Cab-8, which encodes a third type of CAB polypeptide localized in PSI. The protein encoded by Cab-8 is 65% and 60% divergent from the PSI Type I and Type II CAB polypeptides, respectively. The latter two are 65% divergent from each other. Only some short regions of the polypeptides are strongly conserved. The Cab-8 locus maps to chromosome 10, 9 map units from Cab-7, the gene encoding the Type II PSI CAB polypeptide. The Cab-8 gene contains two introns; the first intron matches in position the single intron in the Type II PSII CAB genes and the second intron matches in position the second intron in the Type II PSI CAB gene. Like other CAB genes, Cab-8 is light-regulated and is highly expressed in the leaf and to a lesser extent in other green organs.     

A novel approach to overcome temozolomide resistance in glioma and melanoma: Inactivation of MGMT by gene therapy

Malignant glioma is the most common primary brain tumor. Malignant melanoma is the most malignant of skin tumor. The two malignancies are poorly responsive to conventional treatment regimens such as chemotherapy. Temozolomide (TMZ) is a DNA-alkylating agent used for the treatment of glioma, astrocytoma, and melanoma. Resistance to alkylating agents such as TMZ correlates with increased expression of DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). Several studies in animal models have demonstrated that decreasing MGMT level with gene therapy could overcome TMZ resistance and enhance tumor cell death. In the present review, we provide an overview of recent advances in this field.     

Conservation genetics of small relic populations of silver fir (Abies alba Mill.) in the northern Apennines

Abstract

Small and isolated silver fir populations from the Emilian Apennines (northern Italy) were studied to assess their level of genetic variation and their relationship with Alpine populations. We investigated the variability of two chloroplast microsatellites to analyse the within‐population genetic variability of four peripheral and fragmented Apennine populations and to determine their phylogenetic relatedness to seven Alpine populations covering the entire distribution of silver fir in the Alps. Haplotypic richness and haplotype diversity as well as the fraction of private haplotypes were lower in Apennine populations, evidencing the genetic impoverishment of these stands. The among‐population genetic variability analysis revealed the genetic peculiarity of Apennine populations. Analysis of molecular variance showed that the highest level of the among‐population variation occurs between Alpine and Apennine regions. A neighbour‐joining dendrogram revealed a distinct Apennine cluster that included the closest Alpine population. Our genetic analysis supports a common origin for Emilian Apennine populations, suggesting that these populations are relicts of past large silver fir populations in the northern Apennines. Our results point to a relevant conservation value for these stands, to be considered in their management.     

Transrectal implantation and stability of gold markers in prostate bed for salvage radiotherapy of macroscopic recurrences

Background and purposeThe objective of the study was to verify the stability of gold markers in the prostatic bed (PB) during salvage radiotherapy.Material and methodsSeven patients, diagnosed with a macroscopic nodule visible on MRI, underwent targeted MRI-guided biopsies. Three gold markers were implanted into the PB close to the relapsing nodule for CT/MRI fusion. A dose of 60 Gy was delivered using IMRT to the PB followed by a dose escalation up to 72 Gy to the macroscopic nodule. Daily anterior and left-lateral kV-images were acquired for repositioning. The coordinates of the center of each marker were measured on the two kV-images. The distance variations (Dvar) of the markers in the first session and the subsequent ones were compared.ResultsNo marker was lost during treatment. The average distance between markers was 7.8 mm. The average Dvar was 0.8 mm, in absolute value. A total of 380/528 (72%) Dvar were ⩽1 mm. A Dvar greater than 2 mm was observed in 5.7% of measurements, with a maximum value of 4.8 mm.ConclusionsDespite the absence of the prostate, the implantation of gold markers in the PB remains feasible, with Dvar often less than 2 mm, and could be used to develop new approaches of salvage focal radiotherapy on the macroscopic relapse after prostatectomy.     

Mapping quantitative trait loci controlling silking date in a diallel cross among four lines of maize

 We describe and apply an interval mapping method for quantitative trait locus (QTL) detection using F₃ and testcross progenies derived from F₂ populations obtained from a diallel cross among four elite lines of maize. Linear model-based procedures were used for the test and estimation of putative QTL effects together with genetic interactions including epistasis. We mapped QTL associated with silking date and explored their genetic effects. Ten QTL were detected, and these explained more than 40% of the phenotypic variance. Most of these QTL had consistent and stable effects among genetic backgrounds and did not show significant epistasis. QTL-by-environment interaction was important for four QTL and was essentially due to changes in magnitude of allelic effects. These results show the efficiency of our method in several genetic situations as well as the power of the diallel design in detecting QTL simultaneously over several populations. Received: 2 September 1996 / Accepted: 20 December 1996     

Microsatellite markers isolated from the flightless cormorant (Phalacrocorax harrisi)

Eight polymorphic microsatellite DNA loci were isolated from the flightless cormorant (Phalacrocorax harrisi) for future population genetic studies. Genetic variability was assessed using at least 38 individuals from two populations. Allele numbers ranged from three to nine per locus. Mean observed heterozygosity varied from 0.27 to 0.78. No locus deviated from Hardy-Weinberg (HW) or linkage equilibria in either population. The high levels of detected polymorphism indicate the utility of these markers for population genetic studies of this Galápagos species.     

Combined agronomic and physiological aspects of nitrogen management in wheat highlight a central role for glutamine synthetase

In wheat the period of grain filling is characterized by a transition for all vegetative organs from sink to source status. To study this transition, the progression of physiological markers and enzyme activities representative of nitrogen metabolism was monitored from the vegetative stage to maturity in different leaf stages and stem sections of two wheat (Triticum aestivum) cultivars grown at high and low levels of N fertilization. In the two cultivars examined, we found a general decrease of the metabolic and enzyme markers occurred during leaf ageing, and that this decrease was enhanced when plants were N-limited. Both correlation studies and principal components analysis (PCA) showed that there was a strong relationship among total N, chlorophyll, soluble protein, ammonium, amino acids and glutamine synthetase (GS) activity. The use of a marker such as GS activity to predict the N status of wheat, as a function of both plant development and N availability, is discussed with the aim of selecting wheat genotypes with better N-use efficiency.     

Effect of different isolates of Beauveria bassiana on field populations of Lygus hesperus

Lygus hesperus (Knight) (Hemiptera: Miridae) is a particularly damaging pest of many crops in the Western United States. Current control tactics are chemically based and there is some concern over resistance building up in populations. Based on previous laboratory studies conducted in California and Mississippi, USA, two new isolates of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) were selected for field-testing against L. hesperus in California. Alfalfa plots were treated with one of three isolates of B. bassiana (a commercial isolate, an isolate from CA (WTPB2) or an isolate from MS (TPB3)) or the chemical pesticide Warrior T. More than 75% of the adults collected from plots 3 days after application with B. bassiana were infected but no differences in percentage infection occurred among fungal treatments. In addition, approximately 30% of the insects collected from control plots or plots treated with Warrior T were also infected. PCR analysis using SSR markers revealed that the isolate causing most of the infections in fungus treated plots was the isolate applied. A mix of infections was found in control plots and plots treated with Warrior T. Despite high levels of infection, no significant reductions of adult populations occurred until 10–14 days after application when plots treated with Warrior T or B. bassiana had about half the numbers of adult L. hesperus as the control plots.     

9种石斑鱼遗传多样性和系统发生关系的微卫星分析

利用实验室克隆的13个青石斑鱼微卫星分子标记, 对中国南海海域9种石斑鱼(青石斑鱼、蜂巢石斑鱼、鲑点石斑鱼、黑边石斑鱼、鞍带石斑鱼、赤点石斑鱼、七带石斑鱼、斜带石斑鱼和棕点石斑鱼)进行了遗传多样性和系统发生关系的分析。研究结果显示, 13个微卫星标记共检测到了84个等位基因, 9种石斑鱼中的平均等位基因数、平均多态信息含量(PIC)、平均观测杂合度(Ho)、平均期望杂合度(He)和平均Hardy-Weinberg遗传偏离指数(D)分别在2.69~5.38、0.1976~0.4267、0.4615~0.6239、0.3510~0.4754和0.1097~0.2836之间变动, 说明9种石斑鱼的遗传多样性都处于中等水平。用NJ法进行聚类分析的结果将9种石斑鱼分为3个支系：斜带石斑鱼、棕点石斑鱼和鞍带石斑鱼为第1支; 青石斑鱼、赤点石斑鱼和七带石斑鱼为第2支系; 蜂巢石斑鱼、黑边石斑鱼和鲑点石斑鱼为第3支系, 该支系与第2支系的关系较近。本研究支持将宽额鲈(鞍带石斑鱼)归入石斑鱼属。