Abstract
Excessive cellular accumulation of reactive oxygen species (ROS) due to environmental stresses can critically disrupt plant development and negatively affect productivity. Plant glutathione peroxidases (GPXs) play an important role in ROS scavenging by catalyzing the reduction of H2O2 and other organic hydroperoxides to protect plant cells from oxidative stress damage. RcGPX5, a member of the GPX gene family, was isolated from a traditional medicinal plant Rhodiola crenulata and constitutively expressed in Salvia miltiorrhiza under control of the CaMV 35S promoter. Transgenic plants showed increased tolerance to oxidative stress caused by application of H2O2 and drought, and had reduced production of malondialdehyde (MDA) compared with the wild type. Under drought stress, seedlings of the transgenic lines wilted later than the wild type and recovered growth 1 day after re-watering. In addition, the reduced glutathione (GSH) and total glutathione (T-GSH) contents were higher in the transgenic lines, with increased enzyme activities including glutathione reductase (GR), ascorbate peroxidase (APX), and GPX. These changes prevent H2O2 and O2- accumulation in cells of the transgenic lines compared with wild type. Overexpression of RcGPX5 alters the relative expression levels of multiple endogenous genes in S. miltiorrhiza, including transcription factor genes and genes in the ROS and ABA pathways. In particular, RcGPX5 expression increases the mass of S. miltiorrhiza roots while reducing the concentration of the active ingredients. These results show that heterologous expression of RcGPX5 in S. miltiorrhiza can affect the regulation of multiple biochemical pathways to confer tolerance to drought stress, and RcGPX5 might act as a competitor with secondary metabolites in the S. miltiorrhiza response to environmental stimuli.
Highlights
Plant growth and seed production are subjected to various environmental stresses such as drought, salinity, and temperature extremes (Kilian et al, 2007)
The R. crenulata glutathione peroxidase 5 (RcGPX5) gene was highly expressed under control of a constitutive promoter, and the expression levels were similar in the roots, stems, leaves, flowers, and petals of line 1 (Figure 1C and Supplementary Figure S1B)
In the research presented here, we analyzed the function of the R. crenulata glutathione peroxidase 5 (RcGPX5) gene by ectopic expression in S. miltiorrhiza
Summary
Plant growth and seed production are subjected to various environmental stresses such as drought, salinity, and temperature extremes (Kilian et al, 2007). Plants employ molecular control mechanisms for drought tolerance Some transcription factors such as CBF/DREB (Ravikumar et al, 2014), MYB (Abe, 2002), and NAC (Hu et al, 2006) can be induced by drought stress and modify global gene expression to cope with drought (Zhang et al, 2017). These processes are complex and involve many biochemical pathways that include calcium signaling and biosynthesis of the plant hormone abscisic acid (Knight et al, 1997; Kang et al, 2002; Yunta et al, 2011)
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