Abstract
Plants are regularly exposed to myriads of stress factors that cause tremendous damage to their genetic make-up. To ensure genome stability and survival over several generations under harsher environmental conditions, plants have evolved a unique mechanism for dealing with DNA damage known as the DNA damage response pathway (DDR). It has been proposed that there may exist a relationship between the DNA damage response pathway and abiotic stress response in plants. To further investigate this relationship, we knocked down the soybean suppressor of gamma response 1 gene (GmSOG1), a master regulatory gene of the DDR, in soybean plants and subjected the generated transgenic plants to drought stress analysis. Gene expression analysis of the GmSOG1 gene in drought stressed soybean tissues revealed high levels of expression in buds and young leaves. The root lengths and root fresh weights of transgenic soybean plants grown on Murashige and Skoog media supplemented with Gamborg B5 vitamins (MSB5 media) containing 200 mM mannitol for 10 days were significantly lesser than those of drought stressed wild-type plants. Polyethylene glycol (PEG) induced drought stress assay in vivo resulted in significant damage in transgenic plants compared with wild-type plants. Also, the relative expressions of known drought responsive transcription factors such as GmDREB1 and GmLEA as well as antioxidation related genes like GmAPX and GmCAT were downregulated in transgenic soybean lines relative to wild-type plants. Moreover, wild-type soybean plants accumulated more chlorophyll and less malondialdehyde (MDA) than transgenic lines. A confirmatory experiment in GmSOG1 overexpressing Arabidopsis plants also showed significantly higher survival rates and anti-oxidation enzyme accumulation in drought stressed GmSOG1 overexpressing Arabidopsis lines compared with wild-type plants. These results suggest that the SOG1 gene may play active roles in plant abiotic stress defense.
Highlights
The soybean plant is the most cultivated oil seed crop worldwide, occupying about 6% of the world’s total landmass under cultivation [1]
The root lengths and root fresh weights of transgenic soybean plants grown on Murashige and Skoog media supplemented with Gamborg B5 vitamins (MSB5 media) containing 200 mM mannitol for 10 days were significantly lesser than those of drought stressed wild-type plants
The results of phylogenetic analysis revealed that GmSOG1 was closely related with a homologous protein in Gossypium hirsutum but distantly related with a similar protein in Arabidopsis thaliana (Figure 1(A))
Summary
The soybean plant is the most cultivated oil seed crop worldwide, occupying about 6% of the world’s total landmass under cultivation [1]. The plant contains several useful metabolites and it is the most economically important oil seed crop as well as the leading source of vegetable oil in the world [2]. Research has identified several useful health benefits for the plant including the prevention of cancer, kidney diseases, obesity and diabetes [3]. Drought stress is one of the major factors affecting soybean production, causing about 40% of global yield losses annually [4]. Soybean plants exposed to drought conditions experience reduced nitrogen fixation, loss of CO2 accumulation and reduction in leaf area [6], which results in a decrease in protein synthesis and yield losses [7]
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