Knockdown of GmSOG1 Compromises Drought Tolerance in Transgenic Soybean Lines

Plants are regularly exposed to myriads of stress factors\r\nthat cause tremendous damage to their genetic make-up. To ensure genome stability\r\nand survival over several generations under harsher environmental conditions, plants\r\nhave evolved a unique mechanism for dealing with DNA damage known as the DNA damage\r\nresponse pathway (DDR). It has been proposed that there may exist a relationship\r\nbetween the DNA damage response pathway and abiotic stress response in plants. To\r\nfurther investigate this relationship, we knocked\r\ndown the soybean suppressor of gamma response 1 gene (GmSOG1), a master regulatory gene of\r\nthe DDR, in soybean plants and subjected the generated transgenic plants to drought\r\nstress analysis. Gene expression analysis of the GmSOG1 gene in drought stressed soybean tissues revealed high levels\r\nof expression in buds and young leaves. The root lengths and root fresh weights\r\nof transgenic soybean plants grown on Murashige and Skoog media supplemented with\r\nGamborg B5 vitamins (MSB5 media) containing 200 mM mannitol for 10 days were significantly\r\nlesser than those of drought stressed wild-type\r\nplants. Polyethylene glycol (PEG) induced drought stress assay in vivo resulted\r\nin significant damage in transgenic plants compared with wild-type plants. Also,\r\nthe relative expressions of known drought responsive\r\ntranscription factors such as GmDREB1 and GmLEA as well as antioxidation\r\nrelated genes like GmAPX and GmCAT were downregulated in transgenic\r\nsoybean lines relative to wild-type plants. Moreover, wild-type soybean plants accumulated\r\nmore chlorophyll and less malondialdehyde (MDA) than transgenic lines. A confirmatory\r\nexperiment 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\r\nthat the SOG1 gene may play active roles in plant abiotic stress defense.