Abstract
Plant glutathione S-transferases (GSTs) have been a focus of attention because of their role in herbicide detoxification. OsGSTL2 is a glutathione S-transferase, lambda class gene from rice. Transgenic rice plants overexpressing OsGSTL2 were generated from rice calli by the use of an Agrobacteriumtransformation system. The transgenic rice plants were screened by a combination of hygromycin resistance, polymerase chain reaction (PCR) and Southern blot analysis. Transgenic rice plants overexpressing OsGSTL2 gene showed higher levels of OsGSTL2 transcripts in the absence of any treatment compared to non-transformed rice plants. In the vegetative tissues of transgenic rice plants, the overexpression of the OsGSTL2 increased levels of GST and glutathione peroxidase (GPX) activities, and reduced content of superoxide. Transgenic rice plants also had higher tolerance to glyphosate and chlorsulfuron, which often contaminates agricultural fields. These findings demonstrate the detoxification role of OsGSTL2 in the growth and development of rice plants. It should be possible to apply the present results to crop plants for developing herbicides tolerance and in limiting herbicides availability in the food chain. Key words: Glutathione S-transferase, transgenic rice, overexpression, herbicide resistance.
Highlights
IntroductionAbiotic stresses such as water deficit, high temperature, salinity, cold, heavy metals, mechanical wounding, and exogenous chemicals often impose constraints on plant growth and development (Hasegawa et al, 2000; Sreenivasulu et al., 2007; Vij and Tyagi, 2007)
The 1042 bp HPT gene fragments were detected in the selected independent lines and positive control OsGSTL2 overexpression vector, whereas were not found in non-transformed plants (Figure 2)
The non-transformed rice plants showed more severe yellow and grew more slowly compared with the transgenic rice plants (Figure 7b). These results suggested that overexpression of OsGSTL2 isoenzyme improves glyphosate and chlorsulfuron tolerance of transgenic rice plants
Summary
Abiotic stresses such as water deficit, high temperature, salinity, cold, heavy metals, mechanical wounding, and exogenous chemicals often impose constraints on plant growth and development (Hasegawa et al, 2000; Sreenivasulu et al., 2007; Vij and Tyagi, 2007). Plants have developed a sophisticated and highly complex network of interacting regulatory mechanisms to defend themselves against harmful chemical compounds during evolution. Plants actively detoxify endogenous and exogenous toxins using a three-phase detoxification system that involves cytochrome P450s, Glutathione S-transferases (GSTs, E.C.2.5.1.18) and ATP-binding cassette transporters (Hu et al, 2011). GSTs are an ancient, ubiquitus and multifunctional protein family encoded by a large gene family found in bacteria, fungi, animals and plants (Frova, 2006). Based on the predicted amino acid sequences, GSTs in plants are divided into nine classes: phi, tau, theta, zeta, lambda, glutathione-dependent dehydroascorbate reductase (DHAR), tetrachlorohydroquinone dehalogenase (TCHQD), elongation factor 1 gamma (EF1G) and Microsomal-class GSTs (Basantani and Srivastava 2007; Jain et al, 2010; Hu et al, 2011)
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