水稻镉积累的遗传调控及低镉水稻育种的研究进展与展望

稻田重金属镉污染导致生产的稻米有不同程度的镉积累,长期食用镉污染的稻米危害人体健康甚至致病.因此,研究水稻镉积累的遗传调控机制,培育低镉积累水稻品种,具有重要的理论意义和应用价值.水稻吸收、转运和积累镉的特性存在遗传多样性.近年来,有关水稻吸收和转运镉的遗传调控机制研究取得较大进展,人们鉴定出了多个相关的QTLs、转运...     

镉超积累植物及植物镉积累特性转基因改良研究进展

植物提取修复技术是一项既经济又环保的土壤镉(Cd)污染修复技术,该技术的关键是筛选Cd超积累植物或利用基因工程手段改良植物以提高其Cd积累能力。人们已发现遏兰菜等7种Cd超积累植物及美人蕉等潜在的Cd超积累植物。还发现了许多与Cd耐受和积累能力有关的基因:(1)编码与Cd积累、耐受有关酶的基因,如细菌中的ACC(1-aminocyclopropane-1-carboxylic acid),植物中的PCS(Phytochelatin Synthase)基因;(2)编码金属结合蛋白的基因:MT(Metallothionein)、转运蛋白(P-type ATPase、ABC型转运器)基因;(3)其它相关基因:Hvhsp17、PvSR2(Phaseolus vulgaris stress-related gene number 2)等。并将其中的一些基因转入到其它生物中,提高了其对Cd的耐受性和积累量,为实现Cd污染土壤修复的目标奠定基础。     

植物防御素结构与功能及其抗真菌机制研究进展

植物防御素是一类分子量约为5 kD的阳离子肽,是植物内免疫系统的主要成分之一,参与了多种植物生理生化活动。植物防御素含8个保守半胱氨酸,形成4对链内二硫键来稳定其3条反向平行的β折叠片和1个α螺旋,构成所谓的Csαβ模体结构。植物防御素具有抑制真菌和细菌生长、抑制酶的活性、抑制癌细胞增殖和作为离子通道阻断剂等功能。植物防御素抗真菌机制比较复杂,但它可能首先必须和真菌细胞质膜外侧的鞘脂等复杂脂类结合,引起真菌细胞发生一系列的反应,包括细胞膜通透性增强、胞内活性氧水平增高和诱导真菌细胞凋亡等。但是植物防御素详细的抗真菌机制及其在真菌细胞内作用靶点等有待于深入研究。综述了近年来植物防御素结构、功能及其抗真菌机制等方面的最新研究进展。     

镉低积累水稻资源的镉积累稳定性及遗传相似性分析

以9311为高镉对照,湘晚籼12号为相邻低镉对照,2014-2017年经田间鉴定筛选出的15份镉低积累水稻资源为参试材料,鉴定精米的相对降镉率并筛选出年度间相对降镉率差异不显著的资源;采用45对SSR引物检测15份资源的遗传多样性,提出遗传距离大且相对降镉率高的育种可用资源.2018年试验结果表明,15份低镉水稻资源的...     

植物防御素PD5基因在毕赤酵母中的分泌表达

将植物防御素PD5基因克隆到载体pPIC9的XholⅠ和EcoRⅠ位点之间,得到重组载体pPIC9／PD5。pPIC9／PD5经Bgt Ⅱ线性化,电转化法转入Pichia pastoris GS115,MD和MM平板筛选表型为His^＋Mut^S的转化子,PCR鉴定阳性转化子。转化子D24用BMGY培养至OD600为6．0时,经BMM诱导,上清液用Tricien—SDS—PAGE可检测到目标条带。同时经平板抑菌试验显示,D24的诱导发酵上清液可很好的抑制香蕉枯萎菌（Fusarium oxysporum f.sp.Cubense）及甘蓝黑腐菌[Xanthomona campestris（Smith）Dovosen]的生长。植物防御素PD5基因在毕赤酵母中得到表达。     

施肥对两种苋菜吸收积累镉的影响

通过盆栽试验,研究了生长在5 mg/kg镉(Cd)污染土壤中的两种苋菜(红苋(Amaranthus Paniculatus L.)和绿苋(Amaranthus Paniculatus L.))在3种施肥处理下(N、NP和NPK)的生长状况和对Cd的吸收积累情况。结果表明,两种苋菜能够在污染土壤中正常生长,各器官中叶Cd含量最高,范围为124.1—225.9 mg/kg;根中次之,范围为57.1—100.6 mg/kg;茎中最低,范围为56.2—87.6 mg/kg;富集系数高达22.4—40.2。施加N,NP,NPK肥对两种苋菜器官中的Cd含量和生物量有显著影响。其中,施加NPK肥使红苋和绿苋的生物量分别达到不施肥(对照)处理的3.5和3.2倍,单株提取Cd的总量是对照3.2和5.0倍。综上表明,两种苋菜(红苋和绿苋)具有生物量大、易栽培、施加NPK肥能够大幅增加生物量的同时不减少器官对Cd的吸收等优点,作为Cd污染土壤的修复植物有巨大应用前景。     

小麦幼苗根系镉螯合素

从经Cd~(2+)处理的小麦幼苗根系中分离得到一种镉结合复合物(Cd-BC)。通过SephadexG75,DEAE-52柱层析纯化,鉴定了此复合物性质:(1)紫外吸收光谱在255～265 tim间有一个“肩”,A_(250)/A_(280)>1;(2)在Sephadex G75柱层析上的表观分子量约为10kD,但在SDS-聚丙烯酰胺凝胶电泳上呈现的条带紧接着前沿,分子量非常小;(3)氨基酸组分分析,约90％的氨基酸残基为Glu/Gln,Cys和Gly,三者比例约为4:4:1。结果说明小麦幼苗根系Cd-BC是寡聚肽,是植物镉螯合素(Cd-PCs)的聚合体。     

不同植物防御素的生物信息学分析

采用生物信息学的方法和工具对已在GenBank上注册的花生、鹰嘴豆、合欢、车前草、沙梨、辣椒等植物的防御素的核酸和氨基酸序列作了分析,并对其组成成分、翻译后修饰、导肽、跨膜结构域、疏水性,亲水性、蛋白质二级结构和功能结构域进行预测和推断的结果表明：此类蛋白可能是一具有信号肽的分泌型蛋白,α-螺旋和不规则卷曲是蛋白质二级结构中量最大的结构元件,β-转角和延伸链散布于整个蛋白质中,包含一个gamma-thionin功能结构域。     

人防御素的研究进展

人防御素是近年发现的人体内重要的内源性抗生素,已引起国内外生物和医学研究者的日益重视。这里综述了人防御素的组织分布、分子生物学特点、作用机理、医学及药用价值等方面的研究进展,对采用基因重组方法生产人防御素的方法进行了评述,并展望了防御素的应用前景和发展趋势。     

水稻中镉积累对粘虫的影响

水稻中重金属积累如何影响水稻害虫尚不清楚,本文拟探讨镉积累的水稻对粘虫Mythimna separata幼虫的影响。通过测定不同浓度氯化镉处理的水稻以及人工饲料对粘虫幼虫生长发育的影响,并进一步研究了氯化镉处理水稻中粘虫诱导的防御化合物含量的变化。研究表明水稻叶片中镉的积累导致粘虫幼虫生长减慢、死亡率上升。不同浓度镉处理可以显著提高粘虫诱导的酚胺类化合物对香豆酰腐胺、阿魏酰腐胺、肉桂酰腐胺以及阿魏酰胍丁胺的含量。不同浓度镉添加的人工饲料对粘虫幼虫的存活率无显著影响,而粘虫幼虫取食1 μM和10 μM氯化镉添加的人工饲料后体重反而高于取食未含镉的人工饲料。综上所述,镉积累提高了水稻中粘虫诱导的防御化合物的含量以及水稻对粘虫的抗性,研究结果有利于加深水稻与不同环境胁迫关系的认识。     

Role of the iron transporter OsNRAMP1 in cadmium uptake and accumulation in rice

The heavy metal cadmium (Cd) is toxic to humans, and its accumulation in rice grains is a major agricultural problem. Rice has seven putative metal transporter NRAMP genes, but microarray analysis showed that only OsNRAMP1 is highly up-regulated by iron (Fe) deficiency. OsNRAMP1 localized to the plasma membrane and transported Cd as well as Fe. OsNRAMP1 expression was observed mainly in roots and was higher in the roots of a high-Cd-accumulating cultivar (Habataki) than in those of a low-Cd-accumulating cultivar (Sasanishiki). The amino acid sequence of OsNRAMP1 in the Sasanishiki and Habataki cultivars was found to be 100% identical. These results suggest that OsNRAMP1 participates in cellular Cd uptake and that the differences observed in Cd accumulation among cultivars are because of differences in OsNRAMP1 expression levels in roots.     

Growth and Heavy Metal Binding Properties of Transgenic Chlamydomonas Expressing a Foreign Metallothionein Gene

We have compared the growth rates and cadmium binding capacity of wild-type and transgenic Chlamydomonas reinhardtii cells expressing a foreign class-II metallothionein. We observed that cells expressing metallothionein grew to significantly higher cell densities than wild-type cells in the presence of a toxic cadmium concentration (40 μM). When grown at a low (5 μM) cadmium concentration, cells expressing metallothionein bound twofold more cadmium (0.43 μg Cd)mg Ch1) than wild-type. At cadmium concentrations (40 μM), which induce phytochelatin synthesis in wild-type cells the cadmium binding capacity of both wild-type (79.6 μg Cd)mg Ch1) and transformed cells (86.4 μg Cd)mg Ch1) was similar; however, the transformed cells grew to higher densities than the wild type. These results suggest that under conditions that apparently induce phytochelatin expression, the presence of metallothionein in the cytoplasm reduces heavy metal toxicity. Furthermore, because cells expressing metallothionein grow to higher densities than wild-type cells at a toxic cadmium concentration (40 μM), the transgenic cells sequester more total cadmium (9% of total Cd) from the medium than the wild type (5.5% of total Cd). These results indicate that the trace-metal binding properties of Chlamydomonas can be enhanced through the expression of trace-metal-specific binding proteins.     

Effects of mutual intercropping on cadmium accumulation by the accumulator plants Conyza canadensis,Cardamine hirsuta,and Cerastium glomeratum

In this study, three cadmium (Cd) accumulator species (Conyza canadensis, Cardamine hirsuta, and Cerastium glomeratum) were co-cultured in Cd-contaminated soil in pots to study the effects of intercropping on co-remediation. Only C. canadensis intercropped with C. glomeratum, C. hirsuta intercropped with C. glomeratum, and three-species intercropping increased plant biomass compared with their respective monocultures. The treatments of C. canadensis intercropped with C. glomeratum and three-species intercropping increased the Cd contents in roots and shoots of C. canadensis, whereas the other intercropping treatments decreased or had no significant impact on Cd contents. As for Cd accumulation, the treatments of C. canadensis intercropped with C. glomeratum, C. hirsuta intercropped with C. glomeratum, and three-species intercropping increased Cd accumulation in a single plant compared with that of their respective monocultures, whereas other intercropping treatments decreased Cd accumulation in individual plants. Only the treatments of C. canadensis intercropped with C. glomeratum and C. hirsuta intercropped with C. glomeratum increased Cd accumulation in shoots of a single pot compared with that of their respective monocultures. Therefore, C. canadensis intercropped with C. glomeratum and C. hirsuta intercropped with C. glomeratum may improve the phytoremediation efficiency for Cd-contaminated soil.     

The potential of Thlaspi caerulescens for phytoremediation of contaminated soils

Uptake of Cd, Zn, Pb and Mn by the hyperaccumulator Thlaspi caerulescens was studied by pot trials in plant growth units and in populations of wild plants growing over Pb/Zn base-metal mine wastes at Les Malines in the south of France. The pot trials utilised metal-contaminated soils from Auby in the Lille area. Zinc and Cd concentrations in wild plants averaged 1.16% and 0.16% (dry weight) respectively. The unfertilised biomass of the plants was 2.6 t/ha. A single fertilised crop with the above metal content could remove 60 kg of Zn and 8.4 kg Cd per hectare. Experiments with pot-grown and wild plants showed that metal concentrations (dry weight basis) were up to 1% Zn (4% Zn in the soil) and just over 0.1% Cd (0.02% Cd in the soil). The metal content of the plants was correlated strongly with the plant-available fraction in the soils as measured by extraction with ammonium acetate and was inversely correlated with pH. Bioaccumulation coefficients (plant/soil metal concentration quotients) were in general higher for Cd than for Zn except at low metal concentrations in the soil. There was a tendency for these coefficients to increase with decreasing metal concentrations in the soil. It is proposed that phytoremediation using Thlaspi caerulescens would be entirely feasible for low levels of Cd where only a single crop would be needed to halve a Cd content of 10 g/g in the soil. It will never be possible to remediate elevated Zn concentrations within an economic time frame (<10 yr) because of the lower bioaccumulation coefficient for this element coupled with the much higher Zn content of the soils.     

A two-year field study of phytoremediation using Solanum nigrum L. in China

A two-year in-situ phytoremediation trial was launched in Shenyang Zhangshi (Sewage) Irrigation Area (SZIA). The phytoremediation efficiency of Solanum nigrum L. was determined, by both monitoring the change of soil Cadmium level in the upper 20 cm of soil, and calculating the plant uptake of soil Cd. After two years experimental, by monitoring the soil Cd concentrations, The Cd concentrations decreased on average from 2.75 mg kg^?1to 2.45 mg kg^?1 in the first year and from 2.33 mg kg^?1 to 1.53 mg kg^?1 in the second year, amounting to a decrease by a factor of 10.6% in the first year and 12% in the second year. After two years phytoremediation by S. nigrum, Cd concentrations of the seven experimental plots with S. nigrum growth decreased from 2.75 mg kg^?1 to 1.53 mg kg^?1, a decrease by a factor of 24.9%. And the soil Cd concentration decreased only 2.1% and 1.7% in the bared experimental plot. And the calculating of Cd uptake by S. nigrum shown that, the plants uptake 4.46% and 5.18% of the total soil Cd in 2008 and 2009, while the soil Cd concentrations decreased by a factor of 10.6% in 2008 and 12.1% in 2009.     

水葱对镉的超富集作用及其用于植物修复的潜力

野外观察与研究发现水葱(Scirpus tabernaemontani G.)可以耐受土壤中高浓度的重金属污染,并对镉有很高的生物富集量。实验室水培试验研究了两个主要因素,营养液pH值以及镉含量,对其生物量以及镉富集效果的影响。结果表明,水葱可耐受的高浓度Cd(30mg/L)和大范围pH值变化(3.7～7.7)。当营养液pH值为4.7,Cd含量为25mg/L时,水葱富集的Cd达到最大值:地上部分264.71mg/kg,地下部分234·39mg/kg,平均转运系数1.13。这显示了它用于植物修复镉污染土壤的巨大潜力。     

Aquatic and terrestrial plant species with potential to remove heavy metals from storm-water

Remediation of storm-water polluted with heavy metals should be possible in percolation systems, ponds, or wetlands. The aim of this work was to find plant species for such systems that are efficient in the uptake of Zn, Cu, Cd, and Pb. Plants were collected from percolation and wetland areas and analyzed for heavy metal concentrations. Results showed that submersed and free-floating plants had the capacity to take up high levels of Cu, Zn, and Pb into their shoots. With roots having a concentration factor above 1, the terrestrial plants show efficient stabilization of Cd and Zn and emergent plants show corresponding stabilisation of Zn. In addition, Potamogeton natans, Alisma plantago-aquatica, and Filipendula ulmaria were used in a controlled experiment. The shoots of P. natans and the roots of A. plantago-aquatica were found to accumulate even higher concentrations of Zn, Cu, and Pb than found in the field-harvested plants. Similar results were found for Cd in shoots and Pb in roots of F. ulmaria. Our conclusion is that submersed plant species seem to be the most efficient for removal of heavy metals from storm-water.