Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai, India.
PLoS One. 2011 Jan 21;6(1):e16360. doi: 10.1371/journal.pone.0016360.
Cadmium (Cd) is a major heavy metal pollutant which is highly toxic to plants and animals. Vast agricultural areas worldwide are contaminated with Cd. Plants take up Cd and through the food chain it reaches humans and causes toxicity. It is ideal to develop plants tolerant to Cd, without enhanced accumulation in the edible parts for human consumption. Glutathione transferases (GST) are a family of multifunctional enzymes known to have important roles in combating oxidative stresses induced by various heavy metals including Cd. Some GSTs are also known to function as glutathione peroxidases. Overexpression/heterologous expression of GSTs is expected to result in plants tolerant to heavy metals such as Cd.
Here, we report cloning of a glutathione transferase gene from Trichoderma virens, a biocontrol fungus and introducing it into Nicotiana tabacum plants by Agrobacterium-mediated gene transfer. Transgenic nature of the plants was confirmed by Southern blot hybridization and expression by reverse transcription PCR. Transgene (TvGST) showed single gene Mendelian inheritance. When transgenic plants expressing TvGST gene were exposed to different concentrations of Cd, they were found to be more tolerant compared to wild type plants, with transgenic plants showing lower levels of lipid peroxidation. Levels of different antioxidant enzymes such as glutathione transferase, superoxide dismutase, ascorbate peroxidase, guiacol peroxidase and catalase showed enhanced levels in transgenic plants expressing TvGST compared to control plants, when exposed to Cd. Cadmium accumulation in the plant biomass in transgenic plants were similar or lower than wild-type plants.
The results of the present study suggest that transgenic tobacco plants expressing a Trichoderma virens GST are more tolerant to Cd, without enhancing its accumulation in the plant biomass. It should be possible to extend the present results to crop plants for developing Cd tolerance and in limiting Cd availability in the food chain.
镉（Cd）是一种主要的重金属污染物，对动植物具有高度毒性。世界上许多农业区都受到 Cd 的污染。植物吸收 Cd，通过食物链到达人类并引起毒性。开发耐受 Cd 的植物而不增强可食用部分的积累是理想的，以供人类食用。谷胱甘肽转移酶（GST）是一类多功能酶，已知在对抗各种重金属（包括 Cd）诱导的氧化应激方面具有重要作用。一些 GST 也被认为具有谷胱甘肽过氧化物酶的功能。GST 的过表达/异源表达有望导致植物耐受重金属如 Cd。
在这里，我们报道了从木霉属真菌（一种生防真菌）中克隆出谷胱甘肽转移酶基因，并通过农杆菌介导的基因转移将其导入烟草植物中。通过 Southern 印迹杂交和逆转录 PCR 证实了植物的转基因性质。转基因（TvGST）表现出单基因孟德尔遗传。当表达 TvGST 基因的转基因植物暴露于不同浓度的 Cd 时，与野生型植物相比，它们表现出更高的耐受性，转基因植物表现出较低的脂质过氧化水平。与对照植物相比，当暴露于 Cd 时，表达 TvGST 基因的转基因植物中不同抗氧化酶如谷胱甘肽转移酶、超氧化物歧化酶、抗坏血酸过氧化物酶、愈创木酚过氧化物酶和过氧化氢酶的水平都有所提高。与野生型植物相比，表达 TvGST 的转基因植物中的 Cd 积累量在植物生物量中相似或较低。
本研究结果表明，表达木霉属 GST 的转基因烟草植物对 Cd 具有更高的耐受性，而不会增强其在植物生物量中的积累。应该有可能将本研究结果扩展到作物植物，以开发 Cd 耐受性并限制食物链中 Cd 的可用性。
