Tsyganov Viktor E, Belimov Andrei A, Borisov Alexey Y, Safronova Vera I, Georgi Manfred, Dietz Karl-Josef, Tikhonovich Igor A
All-Russia Research Institute for Agricultural Microbiology, Podbelskogo 3, Pushkin 8, 196608, St Petersburg, Russian Federation.
Ann Bot. 2007 Feb;99(2):227-37. doi: 10.1093/aob/mcl261.
To date, there are no crop mutants described in the literature that display both Cd accumulation and tolerance. In the present study a unique pea (Pisum sativum) mutant SGECd(t) with increased Cd tolerance and accumulation was isolated and characterized.
Ethylmethane sulfonate mutagenesis of the pea line SGE was used to obtain the mutant. Screening for Cd-tolerant seedlings in the M2 generation was performed using hydroponics in the presence of 6 microm CdCl2. Hybridological analysis was used to identify the inheritance of the mutant phenotype. Several physiological and biochemical characteristics of SGECd(t) were studied in hydroponic experiments in the presence of 3 microm CdCl2, and elemental analysis was conducted.
The mutant SGECd(t) was characterized as having a monogenic inheritance and a recessive phenotype. It showed increased Cd concentrations in roots and shoots but no obvious morphological defects, demonstrating its capability to cope well with increased Cd levels in its tissues. The enhanced Cd accumulation in the mutant was accompanied by maintenance of homeostasis of shoot Ca, Mg, Zn and Mn contents, and root Ca and Mg contents. Through the application of La(+3) and the exclusion of Ca from the nutrient solution, maintenance of nutrient homeostasis in Cd-stressed SGECd(t) was shown to contribute to the increased Cd tolerance. Control plants of the mutant (i.e. no Cd treatment) had elevated concentrations of glutathione (GSH) in the roots. Through measurements of chitinase and guaiacol-dependent peroxidase activities, as well as proline and non-protein thiol (NPT) levels, it was shown that there were lower levels of Cd stress both in roots and shoots of SGECd(t). Accumulation of phytochelatins [(PCcalculated) = (NPT)-(GSH)] could be excluded as a cause of the increased Cd tolerance in the mutant.
The SGECd(t) mutant represents a novel and unique model to study adaptation of plants to toxic heavy metal concentrations.
迄今为止，文献中尚未描述同时表现出镉积累和耐受性的作物突变体。在本研究中，分离并鉴定了一种具有增强的镉耐受性和积累能力的独特豌豆（Pisum sativum）突变体SGECd(t)。
采用豌豆品系SGE的甲基磺酸乙酯诱变获得突变体。在含有6微摩尔氯化镉的水培条件下，对M2代耐镉幼苗进行筛选。利用杂交分析确定突变体表型的遗传方式。在含有3微摩尔氯化镉的水培实验中研究了SGECd(t)的若干生理和生化特性，并进行了元素分析。
突变体SGECd(t)具有单基因遗传和隐性表型。它在根和地上部的镉浓度增加，但没有明显的形态缺陷，表明其能够很好地应对组织中增加的镉水平。突变体中镉积累的增加伴随着地上部钙、镁、锌和锰含量以及根部钙和镁含量的稳态维持。通过施用La(+3)并从营养液中排除钙，结果表明在镉胁迫下的SGECd(t)中维持营养稳态有助于提高镉耐受性。突变体的对照植株（即未进行镉处理）根部的谷胱甘肽（GSH）浓度升高。通过测定几丁质酶和愈创木酚依赖性过氧化物酶活性以及脯氨酸和非蛋白硫醇（NPT）水平，结果表明SGECd(t)的根和地上部的镉胁迫水平较低。可以排除植物螯合肽的积累[（计算得出）植物螯合肽 =（NPT）-（GSH）]是突变体镉耐受性增加的原因。
SGECd(t)突变体是研究植物对有毒重金属浓度适应性的一种新颖且独特的模型。
