锰毒及植物耐性机理研究进展

综述了近些年国内外关于锰毒及植物耐锰机理的研究成果,并指出了存在的问题和发展前景。锰毒是酸性土壤上限制作物产量的重要因子,国内外针对锰毒及植物耐受机制进行了相关研究,但进展较为缓慢。锰对植物的毒害效应体现在不同的细胞组织及生理生化水平上,不同植物耐受锰的机理也存在差异性,但大都集中在有机酸的螯合解毒、内部积累、外部排斥及氧化等方面。某些锰胁迫所诱导的基因也被筛选出来,并且部分生物学功能得以鉴定。此外,锰与其他营养元素间的协同或拮抗作用也得以阐述,伴随锰超富积植物-商陆在中国的发现,对锰毒及植物耐性机理的深入研究和探讨,将会对植物修复技术的开展产生理论和实践意义。     

雪里蕻非特异脂质转运蛋白基因的克隆与分析

非特异脂质转运蛋白是植物生命活动中一类重要的活性蛋白,这类蛋白在植物的抗性和防御中行使着重要的功能。近年来研究发现这类蛋白还与植物的有性生殖密切相关。通过已得到的普通白菜的脂质转运蛋白基因BcMF15的核苷酸序列,在其基因全长两侧设计引物,从雪里蕻中克隆得到该类活性蛋白基因,命名为BjLTP (登陆号: EU082009)。该基因全长650bp,不含内含子。不同组织的表达特征分析发现,BjLTP在雪里蕻的花蕾、开放的花中特异表达,推测BjLTP可能与花粉的发育有关。蛋白质特征预测及蛋白序列结构分析发现BjLTP是一个跨膜蛋白,具有显著的疏水区。序列同源比对表明该基因与白花芥蓝、拟南芥等的脂质转运蛋白基因有很高的相似性,证明BjLTP是LTP家族的成员之一。     

Response to nickel in the proteome of the metal accumulator plant Brassica juncea

To gain a comprehensive understanding of the molecular mechanism of heavy metal accumulation in Brassica juncea, comparative proteomic approaches were used to analysis protein profiles in leaf tissues of 6-week-old B. juncea after exposure to 100 µM Ni. Proteomic analysis revealed that 61 protein spots showed 1.5-fold change in protein abundance after Ni exposure as compared to that of corresponding spots in control. Out of the 61 differentially expressed protein spots, 37 protein spots were ambiguously identified by matrix assisted laser desorption ionization/time of flight mass spectrometry (MALDI-TOF MS). The majority of these identified proteins were found to be involved in sulphur metabolism, protection against oxidative stress, clearly indicated that heavy metal sequestration and antioxidant system were activated by Ni treatment. The induced expression of photosynthesis and ATP generation-related proteins were also observed in plants exposed to metals, suggesting the tolerance and accumulation is an energy-demanding process. The identification of these proteins in response to Ni can lead a deep understanding of heavy metal accumulation and tolerance in B. juncea.     

Ion-exchange aspects of toxic metal uptake by Indian mustard

Uptake of lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) as +2 ions by excised roots of Indian mustard was demonstrated to be an ion-exchange process with existing Ca or protons released to the solution. This initial reaction at the root-aqueous interface is important in the uptake of these toxic metals from contaminated soil. Ethylene diamine tetraacetic acid (EDTA)-amended soil for phytoremediation has Pb in anionic form as [Pb-EDTA]2-, which was not taken up by excised roots. In nonliving B. juncea, Pb2+ was translocated from a solution through a cut stem to petiole and leaves much more quickly than anionic [Pb-EDTA]2-. However, in living plants [Pb-EDTA]2- was more quickly translocated from a solution through roots and petiole to leaves than Pb2+. The final amount of uptake on roots of the living plants was the same for both forms of Pb. The present results are important toward understanding the mechanism of phytoremediation of toxic metal-contaminated soil for two reasons: 1) the initial process, uptake of metal ions by roots, was shown to occur by cation exchange and 2) since [Pb-EDTA]2- was not sorbed by excised roots, other factors such as transpiration and active transport are important in applications using EDTA-amended soils contaminated by Pb.     

超富集植物对重金属耐受和富集机制的研究进展

超富集植物对重金属耐受和富集机制的研究成为近年来植物逆境生理研究的热点,在简要总结细胞壁沉淀、重金属螯合效应、酶活性机制和细胞区室化作用的基础上,概述了超富集植物对重金属的耐受机制,讨论了重金属跨根细胞质膜运输,共质体内运输、木质部运输和跨叶细胞膜运输的富集过程。     

Phytoremediation efficiency of Brassica juncea cultivars at vegetative and reproductive growth stages under individual and combined treatment of fluoride and aluminium

The objective of this study was to investigate phytoremediation ability of Brassica juncea cultivars for aluminium (Al) and fluoride (F) independently and in combination (Al + F). Out of 8 cultivars which were treated with Al, F, and (Al + F), 4 cultivars (Bio-902, Pusa-Tarak, CS-14, and Laxmi) were selected for further studies on the basis of growth parameters. These cultivars were exposed to soil (pH 5) supplemented with F (0, 25, 50, and 75 mg kg^?1) and Al (0, 50, 100, and 150 mg kg^?1) independently and in combination (Al + F) (0 + 0, 50 + 25, 100 + 50, and 150 + 75 mg kg^?1). We found that the accumulation of F, Al, and (Al + F) was highest in the roots followed by grains, shoots, and leaves. When the plants were treated with Al or F separately, the accumulation of Al or F were less as compared to when treated in combination (Al + F). Conclusively, the results also showed that maximum tolerance index, uptake, and translocation factor for F were highest in CS-14, Al in Bio-902, and (Al+ F) in Pusa-Tarak, and were found to be the lowest in Laxmi.     

超积累植物吸收重金属的根际效应研究进展

阐述近年来国内外在超积累植物吸收重金属的根际微生态效应这一领域的最新研究成果 ,介绍了根际微生态效应在植物修复中的应用 ,并对当前超积累植物在根际微生态效应研究中的不足之处和需要进一步深入研究的方向进行讨论。     

Development of a technology for commercial phytoextraction of nickel: economic and technical considerations

In recent R&D work, we have made progress in developing a commercial technology using hyperaccumulator plant species to phytoextract nickel (Ni) from contaminated and/or Ni-rich soils. An on-going program is being carried out to develop a genetically improved phytoextraction plant that combines favorable agronomic and Ni accumulation characteristics. Genetically diverse Ni hyperaccumulator species and ecotypes of Alyssum were collected and then evaluated in both greenhouse and field using serpentine and Ni-refinery contaminated soils. Large genetic variation was found in those studies. Mean shoot Ni concentrations in field-grown plants ranged from 4200 to 20400 mg kg^–1. We have been studying several soil management practices that may affect the efficiency of Ni phytoextraction. Soil pH is an important factor affecting absorption of metals by plants. An unexpected result of both greenhouse and field experiments was that Ni uptake by two Alyssum species was reduced at lower soil pH and increased at higher soil pH. At higher pH, plant yield was improved also. In soil fertility management studies, we found that N application significantly increased plant biomass, but did not affect plant shoot Ni concentration. These findings indicate that soil management will be important for commercial phytoextraction. A number of field trials have been carried out to study planting methods, population density, weed control practices, harvest schedule and methods, pollination control, and seed processing. Such crop management studies have improved phytoextraction efficiency and provide a tool for farmers to conduct commercial production. We have done some work to develop efficient and cost-effective methods of Ni recovery. Recovery of energy by biomass burning or pyrolysis could help make phytoextraction more cost-effective. The progress made in our recent studies will enable us to apply this technology commercially in the near future.     

Involvement of Asada-Halliwell Pathway During Phytoremediation of Chromium (VI) in Brassica juncea L. Plants

Brassica juncea (Indian mustard) L. plants were exposed to different concentrations (0.0, 0.1, 0.3 and 0.5 mM) of Chromium (Cr) and harvested after 30 and 60 days of sowing for the analysis of growth parameters, metal uptake and oxidative stress markers. Significant accumulation of Cr (VI) by B. juncea L. plants resulted in the reduced growth and modulations in the pool of various biochemical stress markers. The toxic effects of Cr (VI) on growth and other stress markers (protein content, lipid peroxidation and antioxidative enzymes viz.SOD, CAT, POD, APOX, GR, DHAR and MDHAR) in B. juncea L. were observed to be concentration and time dependent. Effect of Cr (VI) on biochemical parameters was differential and their maximum activities of SOD, POD, APX, GR, DHAR and lipid peroxidation were recorded at 0.5 mM concentration in 30 days old plants. Whereas, trend in the activities of most of the stress markers was reversed in 60 days old plants. The results obtained from the study suggested that Cr (VI) stress inhibited growth of B. juncea L. plants is directly interrelated with its accumulation and resulted in the modulation in activities of various stress markers.     

重金属污染的植物修复及相关分子机制

随着近代工业的发展,土壤重金属污染问题日益严重。重金属即使在极低浓度下仍然可以对人畜造成健康上的威胁,因此迫切需要有效的修复方法对土壤进行修复。生物修复,特别是植物修复目前已经成为重金属污染修复的重要手段之一,了解相关植物的重金属解毒和积累分子机制是提高修复效率、解决重金属污染问题的基础。文中以土壤修复方式为起点,结合植物吸收积累重金属以及解毒的相关分子机制研究,探讨了植物修复的发展现状以及趋势。     

提高榨菜离体培养植株再生频率

采用榨菜“浙桐1号”品种为材料,以MS为基本培养基,通过对不同植物生长调节剂的组合和不同外植体等主要因素的筛选,大幅度提高了榨菜离体培养植株再生频率。结果表明,2mg／L6．BA 0．2mg／L2,4-D的组合较为适宜,其不定芽再生频率可达50％,且外植体以下胚轴为好：而CPPU和2,4-D的适宜组合为1．5mg／L 0．2mg／L,其不定芽再生频率高达66．67％,最适外植体为带柄子叶。同时,研究结果显示,添加0．25～1mg／L的GA,对榨菜已分化的不定芽的伸长有抑制作用;子叶柄和下胚轴外植体的分化具有极性现象。     

表面活性剂对长柔毛委陵菜(Potentilla griffithii var. velutina)修复重金属污染的促进作用

研究了十二烷基苯磺酸钠(SDBS)、十六烷基三甲基溴化铵(CTAB)、聚乙二醇辛基苯基醚(TritonX-100)等不同离子类型的表面活性剂对水稻土中重金属的解吸效果,并采用盆栽实验研究了上述3种表面活性剂对Zn超富集植物长柔毛委陵菜(Potentilla griffithii var. velutina)的生物量、吸收和富集重金属的影响.结果表明:CTAB对水稻土中Zn、Pb、Cd和Cu的解吸效果好于SDBS和TritonX-100,而且3种表面活性剂对各重金属的解吸率大小都为Cd>Zn>Cu>Pb.3种表面活性剂促进长柔毛委陵菜叶、柄和根的生物量增加了0.2～2.5倍,并且长柔毛委陵菜各部位的生物量大小为叶>柄>根.3种表面活性剂都增加了长柔毛委陵菜各部位对Zn、Cd吸收及其叶和柄对Pb、Cu的吸收,同时显著促进Zn、Pb、Cd和Cu从植物根部向地上部转运,从而增加了Zn、Pb、Cd和Cu在长柔毛委陵菜地上部的提取量和分布以及长柔毛委陵菜对Zn、Pb、Cd和Cu的富集能力;因此3种表面活性剂都提高了长柔毛委陵菜修复重金属污染土壤的效率.     

Phytoremediation of aspirin and tetracycline by Brassica juncea

With the increasing release of pharmaceutical drugs in the environment, research is in progress for investigating alternative methods for their remediation. Various studies have shown the phytoremediation potential of Brassica juncea for metals. The current study was aimed at evaluating the phytoremediation potential of B. juncea for two different pharmaceutical drugs i.e. aspirin and tetracycline in in-vitro conditions. The seeds of B. juncea were germinated and grown for a period of 28 and 24 days for aspirin and tetracycline, respectively. The study analyzed the remediation rate of B. juncea for the selected drugs in three different sets of varying concentration along with any phytotoxic effects exerted by the drugs on the seeds. Preliminary results showed that the average remediation rate of aspirin and tetracycline at the end of experiment was approximately 90% and 71%, respectively. As initial drug concentrations were increased in the media, the remediation rate also improved. However, at higher concentrations, the plants showed phytotoxicity as depicted by the decrease in shoot length of the germinated seeds. These preliminary results indicated that B. juncea could tolerate and remediate pharmaceutical drugs such as analgesics and antibiotics.     

茎瘤芥(榨菜)产量生境敏感性的初步研究

运用王夫玉等人提出的生境敏感性评价方法,初步研究了6个茎瘤芥代表品种产量生境敏感性及其与主要性状的关系.结果表明:(1)不同品种,产量生境敏感性不同;据此,可将茎瘤芥品种分为生境敏感型品种、生境弱感型品种和生境钝感型品种.参试品种中,涪丰14和巴中羊角属生境钝感型;半碎叶、蔺市草腰子和涪杂1号属生境弱感型;永安小叶属生境敏感型.(2)产量生境敏感性指数SI(SI愈小,品种对生境反应愈敏感)与Ⅰ(8月20日播种)、Ⅱ(8月30日播种)期瘤茎纵径,与Ⅱ、Ⅲ(9月9日播种)期茎/叶比呈显著或极显著负相关,相关系数分别为-0.848·、-0.835·、-0.872 ·、-0.925··.本文初步提出在涪陵8月20日-8月30日播种的瘤茎纵径和 8月30日至9月9日播种的茎/叶比可作为茎瘤芥产量生境敏感性评价的重要指示性状.     

Overexpression of enzymes involved in glutathione synthesis enhances tolerance to organic pollutants in Brassica juncea

Transgenic Indian mustard (Brassica juncea) overexpressing y-glutamylcysteine synthetase (ECS) or glutathione synthetase (GS) were shown previously to have two-fold higher levels of glutathione and total nonprotein thiols, as well as enhanced cadmium tolerance and accumulation. Here, the hypothesis was tested that these transgenics have enhanced tolerance to organic pollutants, based on the reasoning that many organic xenobiotics are detoxified via conjugation to glutathione. Both the ECS and GS transgenics showed enhanced tolerance to atrazine: while root growth of wildtype seedlings was inhibited 50% by 100 mg L(-1) atrazine, ECS and GS root growth was inhibited 20-30% (P < 0.05). The tolerance of the transgenics to CDNB (1-chloro-2,4-dinitrobenzene). metolachlor, and phenanthrene was also somewhat higher than wild type, but these differences were not as pronounced. Each of the organics treatments significantly enhanced total nonprotein thiol levels in all plant types (2 to 12-fold). Overall, these results suggest that GSH biosynthesis is limiting for atrazine detoxification in Indian mustard and that overexpression of enzymes involved in GSH biosynthesis offers a promising approach to create plants with the enhanced capacity to tolerate not only heavy metals, but also certain organics.     

甘蓝和青花菜杂种小孢子培养

对甘蓝(Brassicaoleraceavar.capitata)×青花菜(Brassicaoleraceavar.italica)的20个杂种及相应的父母本进行游离小孢子培养,并对影响甘青杂种小孢子胚胎发生的主要因子进行探讨,适于小孢子培养的培养基为1/2NLN,附加0.5mgL-1NAA、0.05mgL-1BA、5mgL-1AgNO3、0.2mgL-12,4-D和0.1mgL-1活性炭。结果有14个杂种能产生胚状体,诱导率70%;不同杂种间小孢子胚胎发生频率存在很大差异,最高的是绿洲808×夏宝,平均每蕾16.2个胚。诱导杂种胚状体发生的最佳时期是小孢子单核靠边期至双核期,34℃热激2d有利于小孢子细胞对称分裂。在含糖170gL-1的液体培养基中培养3d,添加低糖(含糖110gL-1)的培养液,可显著提高出胚率。     

Enhancement of heavy metal tolerance and accumulation efficiency by expressing Arabidopsis ATP sulfurylase gene in alfalfa

Abstract

Transgenic alfalfa (Medicago sativa L.) plants overexpressing the Arabidopsis ATP sulfurylase gene were generated using Agrobacterium-mediated genetic transformation to enhance their heavy metal accumulation efficiency. The ATP sulfurylase gene was cloned from Arabidopsis, following exposure to vanadium (V) and lead (Pb), and transferred into an Agrobacterium tumefaciens binary vector. This was co-cultivated with leaf explants of the alfalfa genotype Regen SY. Co-cultivated leaf explants were cultured on callus and somatic embryo induction medium, followed by regeneration medium for regenerating complete transgenic plants. The transgenic nature of the plants was confirmed using PCR and southern hybridization. The expression of Arabidopsis ATP sulfurylase gene in the transgenic plants was evaluated through RT-PCR. The selected transgenic lines showed increased tolerance to a mixture of five heavy metals and also demonstrated enhanced metal uptake ability under controlled conditions. The transgenic lines were fertile and did not exhibit any apparent morphological abnormality. The results of this study indicated an effective approach to improve the heavy metal accumulation ability of alfalfa plants which can then be used for the remediation of contaminated soil in arid regions.     

Selenium accumulation protects plants from herbivory by Orthoptera via toxicity and deterrence

To investigate whether selenium (Se) accumulation in plants provides a chemical defense against generalist insect herbivores, the feeding preference and performance of a mix of orthopteran species were investigated. The selenium hyperaccumulator Stanleya pinnata and accumulator Brassica juncea were used in herbivory studies in the laboratory, and S. pinnata was also used in a manipulative field experiment. In laboratory studies, both crickets and grasshoppers avoided plants pretreated with selenate, while those given no choice died after eating leaves with elevated Se (447 +/- 68 and 230 +/- 68 microg Se g(-1) DW, respectively). B. juncea has previously been shown to accumulate selenate, while S. pinnata hyperaccumulates methyl-selenocysteine. Thus, these findings demonstrate that both inorganic and organic forms of selenium protect plants from herbivory. Grasshoppers fed S. pinnata contained methylselenocysteine in their midgut and absorbed this form into surrounding tissues. In a manipulative field experiment, methylselenocysteine protected S. pinnata from invertebrate herbivory and increased its long-term survival rate over an entire growth season. * In native habitats of selenium hyperaccumulators, orthopterans represent a major group of insect herbivores. Protection offered by organic selenium accumulation against these herbivores may have promoted the evolution of selenium hyperaccumulation in plants.     

Remediation of Nickel-Contaminated Soil by Brassica juncea L. cv. T-59 and Effect of the Metal on Some Metabolic Aspects of the Plant

Among four cultivars of Brassica juncea L., viz., TM-4, TM-2, RH-30, and T-59, cv. T-59 was relatively more tolerant to nickel (Ni) toxicity based on the growth parameters, seedling vigor index, and metal tolerance index. Nickel application inhibited the activity of the nitrate-assimilating enzyme nitrate reductase in the roots, stem, and leaves, whereas the total organic nitrogen, proline, and activity of a polyamine-metabolizing enzyme, diamine oxidase, increased in this tolerant cultivar (T-59). It accumulated a good amount of Ni from the soil in its root and shoot (i.e., 6.0–6.51 μg Ni g^?1 dry weight) during 2 months of cultivation with an 8.0 mM Ni supply in the soil. The data presented in this paper indicate that Ni tolerance and its removal by Indian mustard from subtropical Indian soil is cultivar dependent, possibly due to different genetic and physiological adaptations of the cultivars.     

Investigations into seed dormancy in Grevillea linearifolia, G. buxifolia and G. sericea: anatomy and histochemistry of the seed coat

BACKGROUND AND AIMS: Seeds of east Australian Grevillea species generally recruit post-fire; previous work showed that the seed coat was the controller of dormancy in Grevillea linearifolia. Former studies on seed development in Grevillea have concentrated on embryology, with little information that would allow testing of hypotheses about the breaking of dormancy by fire-related cues. Our aim was to investigate structural and chemical characteristics of the seed coat that may be related to dormancy for three Grevillea species. METHODS: Seeds of Grevillea linearifolia, Grevillea buxifolia and Grevillea sericea were investigated using gross dissection, thin sectioning and histochemical staining. Water movement across the seed coat was tested for by determining the water content of embryos from imbibed and dry seeds of G. sericea. Penetration of intact seeds by Lucifer Yellow was used to test for internal barriers to diffusion of high-molecular-weight compounds. KEY RESULTS: Two integuments were present in the seed coat: an outer testa, with exo-, meso- and endotestal (palisade) layers, and an inner tegmen of unlignified sclerenchyma. A hypostase at the chalazal end was a region of structural difference in the seed coat, and differed slightly among the three species. An internal cuticle was found on each side of the sclerenchyma layer. The embryos of imbibed seeds had a water content six times that of dry seeds. Barriers to diffusion of Lucifer Yellow existed at the exotestal and the endotestal/hypostase layers. CONCLUSIONS: Several potential mechanisms of seed coat dormancy were identified. The embryo appeared to be completely surrounded by outer and inner barriers to diffusion of high-molecular-weight compounds. Phenolic compounds present in the exotesta could interfere with gas exchange. The sclerenchyma layer, together with strengthening in the endotestal and exotestal cells, could act as a mechanical constraint.