Abstract
Glutathione S-transferases (GSTs) constitute a large family of enzymes with a wide range of cellular functions. Recently, plant GSTs have gained a great deal of attention due to their involvement in the detoxification of electrophilic xenobiotics and peroxides under adverse environmental conditions, such as salt, cold, UV-B and drought stress. A previous study reported that a GST gene (CsGSTU8) in tea plant was distinctly induced in response to drought, suggesting this gene plays a critical role in the drought stress response. In this study, by using quantitative real-time PCR (qRT-PCR) and β-glucuronidase (GUS) reporter lines, we further demonstrated that CsGSTU8 was upregulated in response to drought stress and exogenous abscisic acid (ABA) treatments. Overexpression of CsGSTU8 in Arabidopsis resulted in enhanced drought tolerance as indicated by the improved scavenging of excess amounts of reactive oxygen species (ROS) under drought conditions. Furthermore, we found that CsWRKY48 acts as a transcriptional activator and that its expression is induced in response to drought stress and ABA treatment. Electrophoretic mobility shift assays (EMSAs), dual-luciferase (LUC) assays and transient expression assays in tea plant leaves revealed that CsWRKY48 directly binds to the W-box elements in the promoter of CsGSTU8 and activates its expression. Taken together, our results provide additional knowledge of drought stress responses in tea plant.
Highlights
Adverse environmental conditions, especially drought conditions, greatly limit plant growth and development (Shao et al, 2008)
Phylogenetic analysis including all Tau Glutathione S-transferases (GSTs) proteins from Arabidopsis showed that TEA019065 is closely related to AtGSTU8 (Figure 1B); it was named CsGSTU8 in this study
QRT-PCR was used to explore whether CsWRKY48 responds to drought and abscisic acid (ABA) treatment in Longjing-changye seedings, and the results showed that CsWRKY48 was induced in responses to drought and ABA treatment (Figures 5C,D)
Summary
Especially drought conditions, greatly limit plant growth and development (Shao et al, 2008). Several classes of GSTs, including Tau GSTs, have received a great deal of attention in plants due to the assistance of these GSTs in regulating the metabolism of oxidized molecules under drought conditions (Liu et al, 2013b; Xu et al, 2016; Choudhury et al, 2017). The expression level of GSTs in plants was reported to be positively correlated with the rate of oxidized molecule scavenging and to contribute to drought stress tolerance in previous studies (Kumar et al, 2013; Stavridou et al, 2021). Transgenic Arabidopsis plants overexpressing tomato LeGSTU2 show enhanced resistance to drought stress via increased antioxidative enzyme activities for scavenging excess ROS (Xu et al, 2015). Overexpression of a GST gene (ThGSTZ1) from Tamarix hispida improves drought tolerance by enhancing the ability to scavenge ROS (Yang et al, 2014)
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