Three-year field response of young olive trees (Olea europaea L., cv. Arbequina) to soil salinity: Trunk growth and leaf ion accumulation

Irrigated olive is rapidly increasing in arid and semiarid areas, many of which may be negatively affected by soil salinity. We evaluated changes in trunk growth and leaf Cl^–, Na⁺ and K⁺ concentrations in young Arbequina olives (Olea europaea L.) grown in a saline-sodic field over a three-year period. The trunk diameter was measured at the beginning and the end of the 1999 (70 trees), 2000 (59 trees) and 2001 (42 trees) growing periods. Leaves, sampled in August of each year, were analyzed for Cl^–, Na⁺ and K⁺ concentrations. Soil salinity (apparent electrical conductivity, ECa) of each monitored tree was measured 14 times during the 1999–2001 experimental period with an electromagnetic sensor and converted to root zone electrical conductivity of the soil saturation extract (ECe) based on ECa–ECe calibration curves. Salinity tolerance was determined using the Maas and Hoffman threshold–slope response model. Based on salinity thresholds (ECe_thr), the tolerance of olive in terms of trunk growth was high in 1999 (ECe_thr = 6.7 dS m^–1), but declined with age and time of exposure to salts by 30% in 2000 (ECe_thr = 4.7 dS m^–1) and by 55% in 2001 (ECe_thr = 3.0 dS m^–1). Based on the high absolute slopes obtained in all years (values between 16% and 23% dS^–1 m), olive was classified as very sensitive to ECe values above the threshold. Trunk growth thresholds based on leaf ion concentrations varied, depending on years, between 2.6 and 4.0 mg g^–1 (Cl_thr) and between 1.0 and 1.2 mg g^–1 (Na_thr), indicating that Arbequina olive was less sensitive to leaf Cl^– and much more sensitive to leaf Na⁺ than values reported as toxic in greenhouse studies. Leaf K⁺ slightly decreased with increasing salinity, whereas the K⁺/Na⁺ ratio sharply decreased with increasing salinity. We concluded that the initial salinity tolerance of olive was high, but declined sharply with time of exposure to salts and became quite sensitive due primarily to increasing toxic concentrations of Na⁺ in the leaves.     

Apoplastic and cytosolic expression of full‐size antibodies and antibody fragments in Nicotiana tabacum

We compared the expression of a functional recombinant TMVspecific fullsize antibody (rAb29) in both the apoplast and cytosol of tobacco plants and a single chain antibody fragment (scFv29), derived from rAb29, was expressed in the cytosol. Cloned heavy and light chain cDNAs of fullsize rAb29, which binds to TMV coat protein monomers, were integrated into the plant expression vector pSS. The fullsize rAb29 was expressed in the cytosol and targeted to the apoplast by including the original murine antibody leader sequences. Levels of functional fullsize rAb29 expression were high in the apoplast (up to 8.5g per gram leaf tissue), whereas cytosolic expression was low or at the ELISA detection limit. Sequences of the variable domains of rAb29 light and heavy chain were used to generate the single chain antibody scFv29, which was expressed in the periplasmic space of E.coli and showed the same binding specificity as fullsize rAb29. In addition, scFv29 was functionally expressed in the cytosol of tobacco plants and plant derived scFv29 maintained same binding specificity to TMVcoat protein monomers as rAb29.     

Influence of Bt-plants on soil biota and pleiotropic effect of δ-endotoxin-encoding genes

The critical review of experimental conclusions stating environmental safety of transgenic plants reveals that the methods and test materials employed in some studies were inadequate to the goals pursued. A large-scale application of transgenic Bt-plants may result in long-lasting negative impact on the environment. First, the cultivation of these plants leads to accumulation of Bt-toxins in soil. Second, the decomposition of transgenic plants takes significantly longer time compared to that of isogenic lines. Third, the biological activity of soils under transgenic crops is lower than in the control plots. The transfer of δ-endotoxin-encoding genes to the genome of agricultural crops affects simultaneously several entirely different traits of genetically modified plants, thus exerting pleiotropic effects. This gives rise to a paradoxical situation: the genetically engineered crops selected on the trait of resistance to herbivorous insects of the order Lepidoptera become more attractive for herbivores from the other order, Homoptera.     

木本植物基因组DNA提取及鉴定

采用改良后的CTAB法,对山葡萄、软枣猕猴桃、蒙古栎、核桃楸、西伯利亚红松和偃松基因组DNA进行提取。结果表明,所提基因组DNA分子量与λDNA（48 kb）接近,其紫外吸收比在1.66～1.89之间。第3次和第4次上清提取的DNA质量优于第1次和第2次。从提取产量看,每克鲜重提取DNA量最小为15 μg·g^-1（核桃楸第4次上清）,最高的为272 μg·g^-1（山葡萄第3次上清）。西伯利亚红松和偃松第1次和第2次上清基本未提出DNA,第3次和第4次上清中得到了较高质量的DNA。经酶切鉴定和PCR扩增,所提的基因组DNA可以用于进一步研究。     

Engineering Natural and Synthetic Resistance for Nematode Management

Bioengineering strategies are being developed that will provide specific and durable resistance against plant-parasitic nematodes in crops. The strategies come under three categories: (i) transfer of natural resistance genes from plants that have them to plants that do not, to mobilize the defense mechanisms in susceptible crops; (ii) interference with the biochemical signals that nematodes exchange with plants during parasitic interactions, especially those resulting in the formation of specialized feeding sites for the sedentary endoparasites—many nematode genes and many plant genes are potential targets for manipulation; and (iii) expression in plant cells of proteins toxic to nematodes.     

Cell division study in ‘pollen mother cells’ and ‘pollen grains’ of in vivo and ex vitro plants in Drimiopsis botryoides

The various normal and abnormal stages of meiosis and pollen mitosis of Drimiopsis botryoides are described, and a comparison between naturally propagated in vivo and tissue culture derived ex vitro plants in respect to their cytological behaviour presented. We also describe the floral morphology and investigate the relationship between the floral developmental stages and the progression of microgametogenesis. In total, 33 bivalents are observed in diakinesis, which indicate the diploid number 2n = 66 and this number is cross-checked by a haploid set of n = 33 chromosomes in pollen mitosis. Only 6.8% and 4.9% meiotic abnormalities were recorded on in vivo and ex vitro plants, respectively, which led to the formation of non-viable pollen. Finally, the microspores have to develop into tri-cellular male gametophyte. Only 0.2% pollen grains are found with a micro-nucleus. Though the higher pollen viability was recorded on both in vivo (89.3 ± 4.1%) and ex vitro (92.1 ± 4.6%) plants, but surprisingly the pollen germination rate is extremely low with 13.6 ± 1.74% and 21.3 ± 1.55%, respectively. The present study obviously enriches the cytological database of D. botryoides and may help future research on androgenesis and genetic improvement.     

Cell cycle regulation of the microtubular cytoskeleton

The microtubular element of the plant cytoskeleton undergoes dramatic architectural changes in the course of the cell cycle, specifically at the entry into and exit from mitosis. These changes underlie the acquisition of specialized properties and functions involved, for example, in the equal segregation of chromosomes and the correct positioning and formation of the new cell wall. Here we review some of the molecular mechanisms by which the dynamics and the organization of microtubules are regulated and suggest how these mechanisms may be under the control of cell cycle events.     

新疆艾比湖沉积物中免培养放线菌的多样性北大核心CSCD

【目的】采用免培养的方法研究新疆艾比湖湖底沉积物放线菌组成及多样性。【方法】采集并混合5份艾比湖湖底沉积物样本,并提取其总DNA,采用放线菌通用引物对其16S r RNA基因序列进行Touchdown PCR,构建放线菌16S r RNA基因文库。蓝白斑筛选后随机挑选白色克隆分析,利用限制性内切酶HhaⅠ进行酶切分型,挑选具有独特限制性片段差异的阳性克隆进行测序分析。序列经Chimera Check检测,BLAST同源比对及构建16S r RNA基因序列系统发育树。【结果】随机挑选192个白色克隆,其中166个为阳性克隆,选取51个具有独特限制性片段差异的克隆进行序列分析。测序结果进行比对以及Chimera Check检测后,共获得36个可操作单元(Operational Taxonomic Units,OTUs),Gen Bank注册号为KR182090-KR182131。文库覆盖度结果表明克隆文库涵盖了本环境中90.4%的放线菌类群。聚类结果显示,艾比湖湖底沉积物中放线菌分为2个类群,第1个类群属于放线菌门(Actinobacteria),放线菌纲(Actinobacteria)中的放线菌目(Actinomycetales)、丙酸杆菌目(Propionibacteriales)、微球菌目(Micrococcales)和棒杆菌目(Corynebacteriales)4个目,该类群占克隆文库18.1%;另外1个类群属于Unclassified Actinobacteria的类群,分为3个不同的group,占整个克隆文库的81.9%。【结论】新疆艾比湖湖底沉积物中存在多种未知的放线菌类群。     

不同地下水矿化度对柽柳光合特征及树干液流的影响

为揭示柽柳(Tamarix chinensis)光合能力及耗水特征对地下水矿化度的响应规律, 以黄河三角洲建群种——柽柳3年生植株为研究对象, 在1.2 m的潜水水位下, 模拟设置淡水、微咸水、咸水和盐水4种不同的地下水矿化度, 测定柽柳叶片光合-光响应、蒸腾速率和树干液流的日变化。结果表明: 地下水矿化度通过影响土壤盐分可显著影响柽柳光合特性及耗水性能。随地下水矿化度升高, 柽柳叶片净光合速率(P_n)、最大P_n、蒸腾速率、气孔导度、表观量子效率和暗呼吸速率均先升高后降低, 而水分利用效率(WUE)持续降低。淡水、微咸水和盐水处理下, 柽柳P_n光响应平均值分别比咸水处理降低44.1%、15.1%和62.6%; 微咸水、咸水和盐水处理下, 柽柳WUE光响应平均值分别比淡水处理降低25.0%、29.2%和41.7%。随地下水矿化度升高, 柽柳叶片光饱和点先升高后降低, 而光补偿点持续升高, 光照生态幅变窄, 光能利用率变低。淡水和盐水处理下, 柽柳P_n下降分别是非气孔限制和气孔限制引起的。柽柳树干液流速率随地下水矿化度升高而先升高后降低, 咸水处理下树干液流速率日变幅最大, 日液流量最高。淡水、微咸水和盐水处理下日液流速率平均值分别比咸水处理降低61.8%、13.1%和41.9%。咸水矿化度下柽柳有较高的光合特性, 在蒸腾耗水较严重的情况下可实现高效生理用水, 适宜柽柳较好地生长。