Nickel tolerance and copper - nickel co - tolerance in Mimulus guttatus from copper mine and serpentine habitats

Previous work on M. guttatus suggested that nickel tolerance in copper mine populations may also be given by the genes for copper tolerance. It has been shown that copper tolerance in M. guttatus is controlled by a single major gene, plus a number of minor genes (or modifiers) which elevate copper tolerance. Crosses between nickel tolerant individuals from three families and non - tolerants showed that nickel tolerance in M. guttatus is heritable. In order to study the effects of the major copper tolerance gene on copper - nickel co - tolerance in M. guttatus, homozygous copper tolerant and non - tolerant lines were screened against nickel. Significant differences occur between these lines for copper, but were not found when analysed for nickel, indicating that copper - nickel tolerance is not governed by the major gene for copper tolerance. To test whether the minor genes for copper have a pleiotropic effect on nickel tolerance, five selection lines derived from three copper mines (Copperopolis, Penn and Quail) in Calaveras county, California, which vary in degree of tolerance to copper, by the presence or absence of minor copper genes, were also screened against nickel. Two out of three of the lines from Copperopolis showed elevated tolerance to nickel, but two further selection lines derived from Penn and Quail copper mines gave no indication of increased nickel tolerance. These results suggest that the minor genes for copper do not give tolerance to nickel. This was confirmed by the screening of modifier lines, in which modifiers for differing degrees of copper tolerance were inserted into a non - tolerant background. Genotypes possessing fewer copper modifiers yielded higher nickel tolerance than those genotypes which have a greater number of modifiers. Thus nickel tolerance in this species is heritable and under the control of different genes to those producing copper tolerance.     

36个稀有树种的耐性分析

对湖南南岳树木园内引种的鹅掌楸 [Liriodendron chinense (Hemsl.) Sarg.]、桂南木莲(Manglietia chingii Dandy)等36个稀有树种分别进行了耐干旱、耐水涝和耐阴蔽的研究.结果表明,在全自然光照条件下,各树种的暂时凋萎系数为4.97%～11.05%,凋萎系数为1.85%～5.87%.水淹8～68 d,有31个树种出现叶的第1次凋萎,有22种在水淹30～68 d出现死亡,而长叶竹柏(Podocarpus fleuryi Hickel)等5树种水淹73 d未出现叶凋萎.全阴蔽条件下,阴蔽致死亡树种的时间在17～72 d之间,强阴蔽对树种造成伤害.研究结果可为稀有树种的引种、繁育和管理提供科学依据.     

Cloning of heat shock protein genes (hsp70, hsc70 and hsp90) and their expression in response to larval diapause and thermal stress in the wheat blossom midge,Sitodiplosis mosellana

Sitodiplosis mosellana Géhin, one of the most important pests of wheat, undergoes obligatory diapause as a larva to survive unfavorable temperature extremes during hot summers and cold winters. To explore the potential roles of heat shock proteins (hsp) in this process, we cloned full-length cDNAs of hsp70, hsc70 and hsp90 from S. mosellana larvae, and examined their expression in response to diapause and short-term temperature stresses. Three hsps included all signature sequences of corresponding protein family and EEVD motifs. They showed high homology to their counterparts in other species, and the phylogenetic analysis of hsp90 was consistent with the known classification of insects. Expression of hsp70 and hsp90 were highly induced by diapause, particularly pronounced during summer and winter. Interestingly, hsp70 was more strongly expressed in summer than in winter whereas hsp90 displayed the opposite pattern. Abundance of hsc70 mRNA was comparable prior to and during diapauses and was highly up-regulated when insects began to enter the stage of post-diapause quiescence. Heat-stressed over-summering larvae (⩾30 °C) or cold-stressed over-wintering larvae (⩽0 °C) could further elevate expression of these three genes, but temperature extremes i.e. as high as 45 °C or as low as −15 °C failed to trigger such expression patterns. Notably, hsp70 was most sensitive to heat stress and hsp90 was most sensitive to cold stress. These results suggested that hsp70 and hsp90 play key roles in diapause maintenance and thermal stress; the former may be more prominent contributor to heat tolerance and the latter for cold tolerance. In contrast, hsc70 most likely is involved in developmental transition from diapause to post-diapause quiescence, and thus may serve as a molecular marker to predict diapause termination.     

IDENTICAL MAJOR GENE LOCI FOR HEAVY METAL TOLERANCES THAT HAVE INDEPENDENTLY EVOLVED IN DIFFERENT LOCAL POPULATIONS AND SUBSPECIES OF SILENE VULGARIS

Heavy metal tolerant Silene vulgaris plants, originating from different metalliferous sites in Germany and one in Ireland, were crossed to each other and to nontolerant plants from a nonmetalliferous site in The Netherlands. Analysis of the crosses suggested that there were two distinct major gene loci for zinc tolerance among a total of five tolerant populations. The tolerance loci for zinc, copper, and cadmium in the Irish plants were shown to be identical with those in the German populations. It is argued that the occurrence of common major genes for tolerance among different geographically isolated populations must have resulted from independent parallel evolution in local nontolerant ancestral populations. Each of the tolerances studied seems to be controlled by only a few specific major genes.     

线虫耐寒性研究进展

对于分布在温带和寒带的线虫,它们只有战胜冬季寒冷的挑战,才能有利于种群的存在与发展。因此,耐寒性是线虫生物学研究中不可忽视的内容。综述了关于线虫在低温胁迫下的耐寒性测定方法、耐寒对策及耐寒机制等方面的研究进展。线虫的耐寒性和昆虫一样,可通过过冷却点和低温存活率两种指标进行评价,但在具体的实验方法上,线虫耐寒性研究有其不同之处。线虫的耐寒对策和耐寒机制具有多样化。耐寒对策主要有耐冻和避冻,二者能共同渗透于线虫的耐寒过程中。耐寒机制包括特殊发育阶段的形成、低温驯化作用、低分子量抗冻物质的聚集、以及高分子量抗冻蛋白和热休克蛋白的产生,等等。此外,还强调应从多个角度研究线虫的耐寒性,如寒冷敏感型线虫的研究、寄生线虫的耐寒对策研究以及交叉胁迫的研究。     

温度和渗透应激对植物乳杆菌稳定性的影响

在植物乳杆菌对数期后期,高温（43—47℃）、低温（15—25℃）及10-30g/L NaCl等应激处理60min均可使植物乳杆菌耐热性和耐酸性得到较大的提高。其中,尤以高温应激45℃应激处理效果最好,细胞耐热残存率和耐酸残存率较对照分别提高124％和56．8％。     

Heterologous production and biochemical characterization of a new highly glucose tolerant GH1 β-glucosidase from Anoxybacillus thermarum

The enzymatic lignocellulosic biomass conversion into value-added products requires the use of enzyme-rich cocktails, including β-glucosidases that hydrolyze cellobiose and cellooligosaccharides to glucose. During hydrolysis occurs accumulation of monomers causing inhibition of some enzymes; thus, glucose/xylose tolerant β-glucosidases could overcome this drawback. The search of new tolerant enzymes showing additional properties, such as high activity, wide-pH range, and thermal stability is very relevant to improve the bioprocess. We describe a novel β-glucosidase GH1 from the thermophilic Anoxybacillus thermarum (BgAt), which stood out by the robustness combination of great glucose/xylose tolerance, thermal stability, and high Vmax. The recombinant his-tagged-BgAt was overexpressed in Escherichia coli, was purified in one step, showed a high glucose/xylose tolerance, and activity stimulation (presence of 0.4 M glucose/1.0 M xylose). The optimal activity was at 65 °C - pH 7.0. BgAt presented an extraordinary temperature stability (48 h – 50 °C), and pH stability (5.5–8.0). The novel enzyme showed outstanding Vmax values compared to other β-glucosidases. Using p-nitrophenyl-β-d-glucopyranoside as substrate the values were Vmax (7614 U/mg), and K_M (0.360 mM). These values suffer a displacement in Vmax to 14,026 U/mg (glucose), 14,886 U/mg (xylose), and K_M 0.877 mM (glucose), and 1.410 mM (xylose).     

Reversal of osmotic stress effects by gibberellic acid in Brassica campestris. Recovery of hypocotyl growth, protein and RNA levels in the presence of GA

Inhibition of hypocotyl growth by water stress and the antagonistic effect of gibberellic acid was studied in Brassica campestris L. cv. Varuna. Water stress alone inhibited increases in length and fresh weight of the hypocotyl. Increasing levels of GA applied simultaneously reversed the effect of water stress. Growth was related directly to water status and inversely to water saturation deficit. However, in severely stressed seedlings GA increased the length of hypocotyls, while fresh weight showed either no change or was even reduced. Thus a distinct 'uncoupling' between increases in length and water status was observed. GA appears to act partially by increasing the water status of the seedlings and partially by sustaining protein and RNA levels.     

免疫耐受的形成机制

免疫系统如何识别“自己”和“非己”,这是免疫学理论的核心问题。由于在胚胎期自身反应性细胞克隆被排斥,即形成对自身抗原的耐受;但对外源性“非己”成分能产生免疫应答予以清除,此即免疫系统识别“自己”和“非己”的机制。近年来研究证实外周成熟淋巴细胞中存在着自身反应性T细胞,但处于功能失活状态;谓之外周耐受。目前已明确免疫耐受的形成涉及多种机制的参与,包括免疫细胞的相互作用、免疫细胞的分子识别、信号传递、基因表达等不同层次的调节。对免疫耐受机理的研究可为阐明免疫应答及免疫调节的机制提供依据,必将推动免疫学基础理论研究的发展。     

Hydroponic screening of poplar for trace element tolerance and accumulation

Using the nutrient film technique, we screened 21 clones of poplar for growth in the presence of a mix of trace elements (TE) and for TE accumulation capacities. Poplar cuttings were exposed for four weeks to a multipollution solution consisting in 10 microM Cd, Cu, Ni, and Pb, and 200 microM Zn. Plant biomass and TE accumulation patterns in leaves varied greatly between clones. The highest Cd and Zn concentrations in leaves were detected in P. trichocarpa and P. trichocarpa hybrids, with the clone Skado (P. trichocarpa x P. maximowiczii) accumulating up to 108 mg Cd kg(-1) DW and 1510 mg Zn kg(-1) DW when exposed to a multipollution context. Our data also confirm the importance of pH and multipollution, as these factors greatly affect TE accumulation in above ground biomass. The NFT technique applied here to a large range of poplar clones also revealed the potential of the Rochester, AFO662 and AFO678 poplar clones for use in phytostabilization programs and bioenergy production, where production of less contaminated above ground biomass is suitable.     

SOD活性增高的拟南芥晚花突变体具有增强的非生物胁迫耐受性

为了研究晚花突变表型和非生物胁迫耐受性之间是否存在相关性,以遗传背景同为Wassilewskija(Ws-2)的7个拟南芥(Arabidopsis thaliana L.)晚花突变体(CS2235、CS2238、CS2239、CS2240、CS2246、CS2248和CS6208)为材料,通过干旱胁迫、盐胁迫和氧化胁迫实验,发现晚花突变体的耐旱、耐盐和耐氧化性都较野生型(wildtype,WT)强。对叶片失水速率和超氧化物歧化酶(superoxide dismutase,SOD)活性测定结果也表明,晚花突变体的保水能力和SOD活性均高于野生型。相关性回归分析表明SOD活性与耐氧化性、耐旱性、耐盐性之间呈正相关,耐旱性和耐盐性随耐氧化性增强而增强。实验结果表明,这些晚花突变体的表型和非生物胁迫耐受性之间存在相关性。     

The microfilament cytoskeleton plays a vital role in salt and osmotic stress tolerance in Arabidopsis

Although recent studies have suggested that the microfilament (MF) cytoskeleton of plant cells participates in the response to salt stress, it remains unclear as to whether the MF cytoskeleton actually plays an active role in a plant's ability to withstand salt stress. In the present study, we report for the first time the role of MFs in salt tolerance of Arabidopsis thaliana . Our experiments revealed that Arabidopsis seedlings treated with 150 m m NaCl maintained MF assembly and bundle formation, whereas treatment with 250 m m NaCl initially induced MF assembly but subsequently caused MF disassembly. A corresponding change in the fluorescence intensity of MFs was also observed; that is, a sustained rise in fluorescence intensity in seedlings exposed to 150 m m NaCl and an initial rise and subsequent fall in seedlings exposed to 250 m m NaCl. These results suggest that MF assembly and bundles are induced early after salt stress treatment, while MF polymerization disappears after high salt stress. Facilitation of MF assembly with phalloidin rescued wild-type seedlings from death, whereas blocking MFs assembly with latrunculin A and cytochalasin D resulted in few survivors under salt stress. Pre-treatment of seedlings with phalloidin also clearly increased plant ability to withstand salt stress. MF assembly increased survival of Arabidopsis salt-sensitive sos2 mutants under salt stress and rescued defective sos2 mutants. Polymerization of MFs and its role in promoting survival was also found in plants exposed to osmotic stress. These findings suggest that the MF cytoskeleton participates and plays a vital role in responses to salt and osmotic stress in Arabidopsis .     

Greenhouse evaluation of fitness-related reproductive traits in roundup<Superscript>®</Superscript>-tolerant transgenic creeping bentgrass (<Emphasis Type="Italic">Agrostis Stolonifera</Emphasis> L.)

Summary Creeping bentgrass is a very important turfgrass species used extensively on golf course greens, fairways, and tees. One of the challenges of creeping bentgrass management is the control of grassy weeds, most of which respond to herbicides in a similar manner to that of creeping bentgrass. As part of a weed management program for golf courses, Roundup^?-tolerant creeping bentgrass will be simple to employ and more effective in controlling problem weeds than currently available methods. The goal of this research was to evaluate fitness-related reproductive traits in four transgenic creeping bentgrass events modified to express a Roundup^?-tolerant gene, cp4 epsps, to determine if these creeping bentgrass events had gained an unexpected reproductive fitness advantage. We compared transgenic events ASR 333, ASR801 with their nontransformed tissue culture line, C99056L and transgenic events ASR365, ASR368 with their non-transformed tissue culture line, B99061R. Populations of plants from three conventional cultivars were also included for comparison to determine whether significant variations, if present in transgenic events, were novel to the non-transformed organism, Agrostis stolonifera L. Our results showed that none of the four transgenic events surveyed were significantly different from the respective non-transformed tissue culture line plants for the following characteristics: first heading date, anthesis duration, inflorescence length, number of florets per inflorescence, pollen size, and seed-set capacity through open-pollination. One of the transgenic events, ASR333, needed significantly more days for anthesis initiation than the nontransformed tissue culture line, C99056L; while another transgenic event, ASR801, exhibited significantly shorter pollen longevity than plants of the tissue culture line, C99056L. However, ASR801 was not significantly different from the conventional cultivars ‘Penn A-4’ and ‘Penncross’ for pollen longevity. Plants of both transgenic events ASR365 and ASR368 did not differ significantly from plants of the tissue culture line, B99061R, for all characters measured.     

Glycinebetaine accumulation is more effective in chloroplasts than in the cytosol for protecting transgenic tomato plants against abiotic stress

Tomato (Lycopersicon esculentum Mill. cv. Moneymaker) plants were transformed with a gene for choline oxidase (codA) from Arthrobacter globiformis. The gene product (CODA) was targeted to the chloroplasts (Chl-codA), cytosol (Cyt-codA) or both compartments simultaneously (ChlCyt-codA). These three transgenic plant types accumulated different amounts and proportions of glycinebetaine (GB) in their chloroplasts and cytosol. Targeting CODA to either the cytosol or both compartments simultaneously increased total GB content by five- to sixfold over that measured from the chloroplast targeted lines. Accumulation of GB in codA transgenic plants was tissue dependent, with the highest levels being recorded in reproductive organs. Despite accumulating, the lowest amounts of GB, Chl-codA plants exhibited equal or higher degrees of enhanced tolerance to various abiotic stresses. This suggests that chloroplastic GB is more effective than cytosolic GB in protecting plant cells against chilling, high salt and oxidative stresses. Chloroplastic GB levels were positively correlated with the degree of oxidative stress tolerance conferred, whereas cytosolic GB showed no such a correlation. Thus, an increase in total GB content does not necessarily lead to enhanced stress tolerance, but additional accumulation of chloroplastic GB is likely to further raise the level of stress tolerance beyond what we have observed.     

一株耐受低pH、高浓度乳酸及琥珀酸菌株的筛选与鉴定

【目的】通过构建的人工耐酸系统,筛选耐受低pH值、乳酸及琥珀酸的菌株。【方法】构建人工耐酸系统长期驯化菌株,利用不同p H的酸性平板进行筛选,从环境中筛选出一株对低p H值、高浓度乳酸以及琥珀酸有很好耐受性的菌株。通过形态学特征、生理生化特征研究,并结合18S rDNA基因序列分析及分子系统发育树的构建结果,确定菌株的种类。【结果】经过酸性人工系统的长期驯化,筛选分离出一株耐受低pH值、高浓度乳酸以及琥珀酸的菌株WJ-2,经鉴定该菌株为酿酒酵母(Saccharomyces cerevisiae),其最适生长温度为30°C。酸性平板实验显示该菌株能够耐受pH2.5的酸性环境,同时对9%的乳酸及8%的琥珀酸也有很好的耐受性。另外,耐酸菌株WJ-2在pH 2.5、9%乳酸和8%琥珀酸的培养环境中仍能保持相对中性的细胞内pH值。【结论】通过构建人工酸性系统,成功筛选出一株对低pH值、高浓度乳酸以及琥珀酸具有耐受性的菌株——酿酒酵母菌WJ-2,该方法可为筛选具有特定耐受能力菌株提供一个新思路。     

小麦地上部和根系生长的相关性及其在耐Al性筛选中的作用

1　引　　言以往的研究中 ,测定植物根系长度或重量通常以相对根长或相对根系干重作为耐性指标进行耐Ａｌ性的筛选[2 ,4 ,5,8] .但是根系性状在土培或田间试验中不仅取样和测定困难 ,而且易造成根系损伤 ,影响测定的精度 .因此 ,有必要建立简便、可靠且易于测定的筛选指标 .能否采用植株地上部耐性指标来衡量不同小麦基因型的耐Ａｌ性 ?以往涉及植物在铝毒胁迫下地上部和根系生长的耐性指标间的相关性 ,以及地上部耐性指标用于耐Ａｌ性筛选方面的研究甚少 .本研究采用两种筛选方法探讨了 2 4个小麦基因型地上部和根系耐性指标间的相关性 ,旨…     

Change in overwintering mechanism of the Cucujid beetle, Cucujus clavipes

Overwintering larvae of the Cucujid beetle, Cucujus clavipes, were freeze tolerant, able to survive the freezing of their extracellular body fluids, during the winter of 1978–1979. These larvae had high levels of polyols (glycerol and sorbitol), thermal hysteresis proteins and haemolymph ice nucleators that prevented extensive supercooling (the supercooling points of the larvae were ? 10°C), thus preventing lethal intracellular ice formation. In contrast, C. clavipes larvae were freeze suspectible, died if frozen, during the winter of 1982–1983, but supercooled to ～ ? 30°C. The absence of the ice nucleators in the 1982–1983 larvae, obviously essential in the now freeze-susceptible insects, was the major detected difference in the larvae from the 2 years. However, experiments in which the larvae were artifically seeded at ? 10°C (the temperature at which the natural haemolymph ice nucleators produced spontaneous nucleation in the 1978–1979 freeze tolerant larvae) demonstrated that the absence of the ice nucleators was not the critical factor, or at least not the only critical factor, responsible for the loss of freeze tolerance in the 1982–1983 larvae. The lower lethal temperatures for the larvae were approximately the same during the 2 winters in spite of the change in overwintering strategy.