Tolerance of Ricinus communis L. to Cd and screening of high Cd accumulation varieties for remediation of Cd contaminated soils

Response of castor (Ricinus communis L.) to cadmium (Cd) was assessed by a seed-suspending seedbed approach. Length of total radicle was the most sensitive indicator of Cd tolerance among the tested germination and growth characters. The ED₅₀ value for Cd was 11.87 mg L^?1, indicating high Cd tolerance in castor. A pot experiment was conducted by growing 46 varieties of castor under CK (without Cd) and Cd1 (10 mg kg^?1 of Cd) and Cd2 (50 mg kg^?1 of Cd) treatments to investigate genotype variations in growth response and Cd accumulation of castor under different Cd exposures. Castor possessed high Cd accumulation ability; average shoot and root Cd concentrations of the 46 tested varieties were 21.83 and 185.43 mg kg^?1, and 174.99 and 1181.96 mg kg^?1 under Cd1 and Cd2, respectively. Great variation in Cd accumulation was observed among varieties, and Cd concentration of castor was genotype dependent. The correlation between biomass and Cd accumulation was significantly positive, while no significant correlation was observed between Cd concentration and Cd accumulation, which indicated that biomass performance is the dominant factor in determining Cd accumulation ability.     

镉在水花生叶片中的亚细胞分布及其毒理学

以水花生为试验材料,研究了不同浓度镉(Cd)(0、0.05、0.1、0.2、0.4 mmol·L-1)胁迫下水花生叶中Cd及矿质元素的亚细胞分布、抗氧化能力、叶绿素、可溶性蛋白和植物络合素(PCs)含量的变化.结果表明:随着培养液中Cd浓度的增加,叶片内各亚细胞组分中Cd含量显著增加,但分布不均,主要积累在细胞壁,其次为可溶成分,线粒体和叶绿体中分布最少.Cd处理浓度大于0.2 mmol·L-1时,呈现Cd向水花生叶的可溶成分中分配增加、细胞壁中分配减少的趋势.矿质元素的吸收明显失衡,表现为各亚细胞组分中Ca含量显著增加且主要分布在细胞壁中,细胞壁和可溶成分中P和K含量不断降低,叶绿体中Mg和Fe的含量逐渐减少.叶绿素和可溶性蛋白含量持续下降.谷胱甘肽和抗坏血酸含量先升后降,总抗氧化能力(T-AOC)不断提高,PCs大量累积.水花生对水体中的Cd有一定耐性,且Cd在亚细胞结构中的富集量与其毒性间具有明显的剂量-效应关系;亚细胞中矿质元素的紊乱以及叶绿素和可溶性蛋白含量的显著降低,Cd在亚细胞中的积累对植物体造成了明显的毒害作用;Ca在细胞壁中的累积以及PCs和T-AOC水平的提高说明水花生具有较强的抗性;PCs的合成量与Cd对水花生的毒性变化有一定的相关性,可以作为Cd胁迫的生物标记物.     

Opportunities and feasibilities for biotechnological improvement of Zn, Cd or Ni tolerance and accumulation in plants

Metals contaminate the soil when present in high concentrations causing soil and ultimately environmental pollution. “Phytoremediation” is the use of plants to remove pollutants from contaminated environments. Plants tightly regulate their internal metal concentrations in a process called “metal homeostasis”. Some species have evolved extreme tolerance and accumulation of Zn, Cd and Ni as a way to adapt to exposure to these metals. Such traits are beneficial for phytoremediation, however, most natural metal hyperaccumulator species are not adapted to agriculture and have low yields. A wealth of knowledge has been generated regarding metal homeostasis in plants, including hyperaccumulators, which can be used in phytoremediation of Zn, Cd and Ni. In this review, we describe the current state of Zn, Cd and Ni physiology in plants and the underlying molecular mechanisms. The ways to efficiently utilize this information in designing high biomass metal accumulator plants are discussed. The potential and application of genetic modification has extended our understanding about the mechanisms in plants dealing with the metal environment and has paved the way to achieve the goal of understanding metal physiology and to apply the knowledge for the containment and clean up of metal contaminated soils.     

Cadmium-induced oxidative stress in two potato cultivars

A hydroponic experiment was carried out to characterize the oxidative stress responses of two potato cultivars (Solanum tuberosum L. cvs. Asterix and Macaca) to cadmium (Cd). Plantlets were exposed to four Cd levels (0, 50, 100, 150 and 200 μM) for 7 days. Cd concentration was increased in both roots and shoot. Number of sprouts and roots was not decreased, whereas Cd treatment affected the number of nodal segments. Chlorophyll content and ALA-D activity were decreased in both cultivars, whereas carotenoids content was decreased only in Macaca. Cd caused lipid peroxidation in roots and shoot of both cultivars. Protein oxidation was only verified at the highest Cd level. H₂O₂ content was increased in roots and shoot of Asterix, and apparently, a compensatory response between roots and shoot of Macaca was observed. SOD activity was inhibited in roots of Asterix at all Cd treatments, whereas in Macaca it was only increased at two highest Cd levels. Shoot SOD activity increased in Asterix and decreased in Macaca. Root CAT activity in Asterix decreased at 100 and 150 μM, whereas in Macaca it decreased only at 50 μM. Shoot CAT activity was decreased in Macaca. Root AsA content in Macaca was not affected, whereas in shoot it was reduced at 100 μM and increased at 200 μM. Cd caused increase in NPSH content in roots and shoot. Our results suggest that Cd induces oxidative stress in both potato cultivars and that of the two cultivars, Asterix showed greater sensitivity to Cd levels.     

外源抗坏血酸对镉胁迫下黑藻抗氧化系统的保护作用

研究了不同浓度抗坏血酸(ascorbic acid,AsA)对5 mg·L^-1Cd²⁺胁迫下黑藻（Hydrilla verticillata）体内超氧阴离子(O₂^-)产生速率、过氧化氢(H₂O₂)含量、抗坏血酸和谷胱甘肽(GSH)含量,以及超氧化物歧化酶(SOD)、超氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的影响.结果表明,与单一Cd²⁺胁迫相比,随着外源AsA浓度的升高,黑藻体内活性氧生成速率逐步降低;抗氧化物质AsA先升后降,GSH缓慢升高;抗氧化酶APX和CAT活性先升后降,POD活性逐步下降,并接近正常状态,对SOD活性影响不大.可见AsA能够有效缓解Cd²⁺对黑藻的毒害,且60 mg·L^-1浓度下的缓解效果最好.     

外生菌根真菌对重金属铜镉污染土壤中油松生长和元素积累分布的影响

该实验选取处于生长期的油松(Pinus tabulaeformis)幼苗,研究土壤Cu、Cd胁迫条件下,美味牛肝菌(Boletus edulis)单独接种、红绒盖牛肝菌(Xerocomus chrysenteron)与美味牛肝菌混合接种处理,对油松幼苗的生长和重金属积累分布状况的影响,探讨不同接种对油松抗性的影响。研究发现,菌根接种不仅促进寄主油松的生长发育和生物量积累,而且显著降低油松体内的重金属积累浓度,减少重金属由根部向植物茎叶部分的转运。与单一接种相比,混合接种可以更加有效地缓解重金属对寄主的生物毒性,减少土壤中重金属元素向油松体内的转运。这种优势在高浓度的重金属胁迫环境下尤为明显。该实验中,在3 mg·kg^-1 Cd胁迫下,混合菌根油松的茎叶和根部Cd浓度仅为未接种对照的59.1%和70.7%,比单一菌根降低了11.3%和18.1%,而混合菌根植物的茎叶和根部生物量干重则分别为未接种对照的1.14和1.20倍,单一菌根为未接种对照的1.18和1.17倍。在400 mg·kg^-1Cu胁迫下,混合菌根植物茎叶和根部的干重分别是未接种植株的1.01和1.09倍,而混合菌根植物茎叶和根部的Cu浓度仅为未接种植株的61.8%和79.6%,比Boletus edulis菌根植物的Cu积累浓度下降了0.7%和3.8%。     

胞外三磷酸腺苷通过一氧化氮调节镉诱导的氧化压力和细胞死亡

采用液体悬浮培养方法,研究胞外三磷酸腺苷(ATP)通过一氧化碳(NO)调节镉诱导对烟草(Nicotiana tabacum L.)悬浮细胞氧化压力和死亡水平的影响。结果显示,镉离子(Cd^2+)可以以剂量依赖的模式引起烟草悬浮细胞氧化压力和死亡水平的上升,而施加外源ATP可有效缓解Cd^2+诱导的氧化压力和细胞死亡。进一步研究发现,和外源ATP的缓解作用相似,NO的供体硝普钠(SNP)同样可以缓解Cd^2+诱导的氧化压力和细胞死亡水平的上升;且NO合成抑制剂(L-NAME)可部分解除外源ATP的缓解作用。研究结果表明外源ATP可通过NO调节镉诱导的氧化压力和细胞死亡。     

Cd胁迫对杂交水稻及其亲本叶片丙二醛含量的影响

以15份杂交水稻及其亲本为材料,采用水培试验研究了不同Cd2＋浓度胁迫对水稻叶片丙二醛（MDA）含量的影响。结果表明：（1）在不同Cd处理水平和生育时期,保持系叶片MDA含量存在差异,如D83B叶片MDA含量各处理显著高于对照（p〈0.05）,MDA积累水平较高,受到Cd严重胁迫,而Ⅱ-32B在两个生育时期受低Cd浓度的影响不大,与对照差异不显著,且随着Cd浓度的增大,MDA含量均表现出较低的MDA积累水平,因此保持系Ⅱ-32B是一种较好的保持系材料。（2）Cd胁迫对恢复系各材料叶片MDA的影响不同,其中以R527、R498叶片MDA积累最明显,孕穗期和灌浆期各处理均显著高于对照,其余恢复系材料受不同Cd2＋浓度的影响,MDA积累不稳定。（3）同一保持系（Ⅱ-32B）与不同恢复系（R498、R549、R892）组合配制的3个杂交稻叶片在MDA含量的增加幅度上表现不同,其中Ⅱ优498、Ⅱ优892受Cd影响较小,无论在孕穗期还是灌浆期叶片MDA含量增幅相对较小,而Ⅱ优549受Cd严重胁迫,各处理均显著高于对照,MDA积累增幅最大。（4）同一恢复系（R498）与不同保持系（Ⅱ-32B、D62B）配制的杂交稻叶片MDA含量亦不同,如D优498仅在孕穗期低浓度下MDA较对照有所降低,其余各处理MDA均积累较多,而Ⅱ优498MDA含量随着Cd浓度的增加,MDA增幅相对较小,可见水稻亲本对子代MDA的积累存在差异,可根据优良亲本,寻找优势组合,培育出抗Cd性强的杂交水稻。     

The crystal structure of arginyl-tRNA synthetase from Homo sapiens

Arginyl-tRNA synthetase (ArgRS) is a tRNA-binding protein that catalyzes the esterification of l-arginine to its cognate tRNA. l-Canavanine, a structural analog of l-arginine, has recently been studied as an anticancer agent. Here, we determined the crystal structures of the apo, l-arginine-complexed, and l-canavanine-complexed forms of the cytoplasmic free isoform of human ArgRS (hArgRS). Similar interactions were formed upon binding to l-canavanine or l-arginine, but the interaction between Tyr312 and the oxygen of the oxyguanidino group was a little bit different. Detailed conformational changes that occur upon substrate binding were explained. The hArgRS structure was also compared with previously reported homologue structures. The results presented here may provide a basis for the design of new anticancer drugs, such as l-canavanine analogs.