Effect of lead stress on mineral content and growth of wheat (Triticum aestivum) and spinach (Spinacia oleracea) seedlings

Lead (Pb) is the most common heavy metal contaminant in the environment. Pb is not an essential element for plants, but they absorb it when it is present in their environment, especially in rural areas when the soil is polluted by automotive exhaust and in fields contaminated with fertilizers containing heavy metal impurities. To investigate lead effects on nutrient uptake and metabolism, two plant species, spinach (Spinacia oleracea) and wheat (Triticum aestivum), were grown under hydroponic conditions and stressed with lead nitrate, Pb(NO₃)₂, at three concentrations (1.5, 3, and 15 mM).Lead is accumulated in a dose-dependent manner in both plant species, which results in reduced growth and lower uptake of all mineral ions tested. Total amounts and concentrations of most mineral ions (Na, K, Ca, P, Mg, Fe, Cu and Zn) are reduced, although Mn concentrations are increased, as its uptake is reduced less relative to the whole plant’s growth. The deficiency of mineral nutrients correlates in a strong decrease in the contents of chlorophylls a and b and proline in both species, but these effects are less pronounced in spinach than in wheat. By contrast, the effects of lead on soluble proteins differ between species; they are reduced in wheat at all lead concentrations, whereas they are increased in spinach, where their value peaks at 3 mM Pb.The relative lead uptake by spinach and wheat, and the different susceptibility of these two species to lead treatment are discussed.     

Simulated beetle defoliation on willow genotypes in mixture and monotype plantations

The effect of simulated beetle damage (0%, 25%, 50% and 75% mechanical defoliation) on 12 willow genotypes, grown in short‐rotation coppice, was studied in a modified criss‐cross experimental design. The design enabled the above‐ground effects of monoculture and mixed planting to be assessed. Repeated measurements were modelled to produce derived variables in terms of time or, more appropriately, in terms of accumulated day length (i.e. ‘developmental time’) units. These derived variables were then analysed using the REsidual Maximum Likelihood (REML) method implemented in GenStat? (2001) . No significant competition effect between the genotypes due to planting regime was detected. Genotypes Salix viminalis × Salix schwerinii‘Beagle’ and S. viminalis × S. schwerinii‘Torhild’ were found to have the greatest rate of increase in leaves regardless of defoliation and also the greatest height prior to defoliation. Genotype Salix dasyclados‘Loden’ showed the highest rate of growth under the stress of defoliation. When assessing height at the end of the growing season, S. viminalis × S. schwerinii‘Olof’ was the highest genotype for 25% and 75% levels of defoliation, but genotypes Salix aurita × Salix cinerea‘Delamere’, Loden and S. viminalis × Salix burjatica‘Ashton Parfitt’ appeared to be most tolerant by having consecutively lower base day lengths (i.e. increasing the accumulation of developmental units and the length of the growing season) for increasing defoliation. Shorter genotypes tended to be more tolerant, but of the higher genotypes reaching a control height of greater than 3 m by the end of the growing season, S. viminalis × S. schwerinii‘Tora’ and Beagle performed best to 50% defoliation.     

Oncogenic potential of Nrf2 and its principal target protein heme oxygenase-1

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential component of cellular defense against a vast variety of endogenous and exogenous insults, including oxidative stress. Nrf2 acts as a master switch in the circuits upregulating the expression of various stress-response proteins, especially heme oxygenase-1 (HO-1). Paradoxically, however, recent studies have demonstrated oncogenic functions of Nrf2 and its major target protein HO-1. Levels of Nrf2 and HO-1 are elevated in many different types of human malignancies, which may facilitate the remodeling of the tumor microenvironment making it advantageous for the autonomic growth of cancer cells, metastasis, angiogenesis, and tolerance to chemotherapeutic agents and radiation and photodynamic therapy. In this context, the cellular stress response or cytoprotective signaling mediated via the Nrf2–HO-1 axis is hijacked by cancer cells for their growth advantage and survival of anticancer treatment. Therefore, Nrf2 and HO-1 may represent potential therapeutic targets in the management of cancer. This review highlights the roles of Nrf2 and HO-1 in proliferation of cancer cells, their tolerance/resistance to anticancer treatments, and metastasis or angiogenesis in tumor progression.     

秦岭南坡锐齿栎林的生态环境及其营养积累

秦岭锐齿栎林 (含 0～ 6 0cm土层 )营养元素总储量达 182 .6 4 5～ 394 .70 1t·hm-2 ,植被占 0 .5 9%～2 .13% ;林分生物量为 131.713～ 5 0 3.82 2t·hm-2 ,乔木层占 92 .1%～ 99.2 % ;凋落物层现存量和营养元素积累量分别为 2 .897～ 33.999t·hm-2 和 10 4 .339～ 1136 .5 36kg·hm-2 .在一定范围内 ,林分生物量和营养元素积累量随密度的增加而增大 ;立地、林分条件相似的林分 ,生物量和营养元素积累量与林龄呈正相关 .林分针叶树占的比例越大 ,营养元素积累量越小 ,而且对生物量的影响远小于对营养元素积累量的影响 .在同一地区 ,立地、林分状况相似 ,林型不同 ,生物量及营养元素积累量差别不大 ,树种组成和林型不同林分的生物量和营养元素积累量均不同 .不同地区 ,生态和林分条件相似的林分的生物量和营养元素积累量也有差异 ;林型、结构相似林分生物量和营养元素积累量南坡 >北坡 ,中段 东段≈西段 .林分对营养元素利用率与海拔呈负相关 ,且南坡 >北坡 ,中段 >东西段 ,中段 >西段 >东段 .     

南瓜SWEET蛋白家族的全基因组鉴定与进化分析

SWEET(sugar will eventually be exported transporter)家族是一种新型的糖转运体,该家族基因在碳水化合物运输、发育、环境适应性和寄主-病原相互作用等多个过程中发挥着重要作用.为更好地了解南瓜发育的分子机理,该研究基于已知的南瓜基因组数据库,利用生物信息学方法对中国南瓜SW...     

The relationship between human cytomegalovirus infection and atherosclerosis development

Transport characteristics of essential trace elements as zinc, copper, selenium and iron have been studied in maternal–fetal direction in normal pregnancies, using in vitro perfusion of human placental lobules. Solutions of trace elements corresponding to twice the physiological concentrations were injected (100 l bolus) into the maternal arterial perfusate. Serial perfusate samples were collected every 30 sec from venous outflows for a study period of 5 min. Concentrations of these trace elements and their transport kinetics were determined. Transport fractions (TF) of zinc, copper, selenium and iron averaged 0.21, 0.49, 0.55 and 0.10% of maternal load respectively. Other parameters such as area under the curve, clearance, elimination constant, absorption and elimination rates showed some significant differences between the various elements. Copper and selenium appear to be transported passively in maternal–fetal direction, while for iron and zinc, role of active transport for transfer across the human placental membrane cannot be discounted. We speculate that alterations in copper: zinc TR50 (transport rate for 50% efflux) and TF ratios could serve as useful indicators for assessing placental transport status of these essential elements in complicated pregnancy states.     

An embryogenic cell line of maize from A188 (Minnesota) contains Mu1-like elements

The maize inbred line A188 is popularly used for the production of embryogenic cell lines. A188, maintained at the University of Minnesota, was found upon molecular analysis to contain 2 to 4 copies of a DNA sequence very similar in structure to transposable Mu1 elements, which have been implicated in Robertson's Mutator system. These Mu1-like elements are in the same chromosomal locations in sibling plants and in A188 cell cultures derived from them. This suggests that the elements are in an inactive state and do not undergo transposition. However, we have observed that they are not modified at the target sites for certain restriction endonucleases. Possible causes for the apparent lack of transposition of these Mu1-like elements in these A188 lines are discussed. Inasmuch as the elements do not transpose, they must be maintained in this line as homozygous Mendelian elements by self-pollination.Journal paper no. J-12269 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011. Project 2707.     

Genetic and developmental basis for parallel evolution and its significance for hominoid evolution

Greater understanding of ape comparative anatomy and evolutionary history has brought a general appreciation that the hominoid radiation is characterized by substantial homoplasy.^1–4 However, little consensus has been reached regarding which features result from repeated evolution. This has important implications for reconstructing ancestral states throughout hominoid evolution, including the nature of the Pan‐Homo last common ancestor (LCA). Advances from evolutionary developmental biology (evo‐devo) have expanded the diversity of model organisms available for uncovering the morphogenetic mechanisms underlying instances of repeated phenotypic change. Of particular relevance to hominoids are data from adaptive radiations of birds, fish, and even flies demonstrating that parallel phenotypic changes often use similar genetic and developmental mechanisms. The frequent reuse of a limited set of genes and pathways underlying phenotypic homoplasy suggests that the conserved nature of the genetic and developmental architecture of animals can influence evolutionary outcomes. Such biases are particularly likely to be shared by closely related taxa that reside in similar ecological niches and face common selective pressures. Consideration of these developmental and ecological factors provides a strong theoretical justification for the substantial homoplasy observed in the evolution of complex characters and the remarkable parallel similarities that can occur in closely related taxa. Thus, as in other branches of the hominoid radiation, repeated phenotypic evolution within African apes is also a distinct possibility. If so, the availability of complete genomes for each of the hominoid genera makes them another model to explore the genetic basis of repeated evolution.     

南方稀土采矿恢复地土壤稀土元素含量及植物吸收特征

通过野外取样调查和室内ICP-MS测定,研究了福建省长汀县稀土矿治理地土壤和主要植物中稀土元素的含量、分布以及转移特征.结果表明:稀土矿治理地的土壤养分含量较低;土壤中稀土元素的含量为507.40～841.37 mg· kg-1,高于对照地土壤的含量.稀土矿治理地土壤中稀土元素主要为交换态,其含量占总量的61％～98％.稀土矿治理地土壤中稀土元素从原来偏单一的交换态转变为多种形态共存,其中有机态含量显著升高.植物根、茎、叶中稀土元素含量分别为40.27～986.01、5.14 ～ 206.58、6.81 ～ 2364.51mg·kg-1.稀土元素在植物各器官中含量水平除芒萁为叶＞根＞茎,其他植物均表现为根＞叶＞茎.根据不同植物吸收和积累稀土元素的差异,可将矿区治理地植物分为富集型和根部囤积型植物.芒萁属于富集型植物,桉树、高羊茅、宽叶雀稗、木荷和油茶属于根部囤积型植物.