Knockdown of GmSOG1 Compromises Drought Tolerance in Transgenic Soybean Lines

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.