Research On The Expression And Stress Resistance Of SOS Gene In Alfalfa

Alfalfa is a perennial legume forage with high nutritional value,But the soil salinization seriously restricts the yield of alfalfa.The use of conventional breeding methods for their germplasm improvement is not only a long cycle and low efficiency.With the development of modern molecular biology technology,improving the salt tolerance of Alfalfa by genetic engineering has become the main mode of Alfalfa breeding.Based on the efficient regeneration system,using the cotyledon as explants,the SOS 1-SOS2-SOS3 gene from Arabidopsis thaliana were incorporated into Algonquin by tumefaciens-mediate transformation technology.The transgenic plants were obtained and identified.The main results are shown as follows:(I)12 transgenic plants were identified by PCR,herbicide resistance screening and RT-PCR,which showed that the the positive rate was 80%.And the foreign genes had been integrated into the genome of transgenic plants by Southern blotting and RT-PCR.(2)The salt resistance of potted plants was evaluated by different concentration(100?200 and 300 mmol/L)of NaCl in 6 days.The results are as follows:There was significant difference between the transgenic and wild-type plants.Compared with the transgenic plants,the leaves of the wild type plants became yellow,and showed signs of wilting.Under different salt treatment,the height of all plants were increased,but the growth of transgenic plants was significantly higher than that of wild plants.Determination of physiological and biochemical indexes,the results showed that with the increase of processing time,the chlorophyll content of all plants were decreased,but the chlorophyll content of wild type plants was lower than that of transgenic plants.Under 100 and 200 mmol/L NaCl treatment,the membrane permeability,SOD activity and Pro content of transgenic plants were lower than that of wild type plants.However,the POD activity,CAT activity and soluble sugar were higher than that of wild type.But beyond that,the content of MDA in all the plants decreased,and the decline of wild type plants was more obvious.The contents of Na+ and K+ in roots of transgenic and wild-type plants showed that after treatment,the accumulation of Na+ in roots of transgenic plants was less than in wild type plants,while K+ content was more than that of wild-type plants.In summary,under 100 and 200 mmol/L NaCl treatment,Transgenic plants play a role in SOS pathway,promoting Na+ efflux and reducing the ion toxicity of plant cells.As a result,the salt resistance of Alfalfa increased.However,there was no significant difference between the transgenic and wild-type plants under 300 mmol/L NaC treatment.(3)The drought resistance of hydroponic plants was evaluated by different concentration(5%?10%and 20%)of PEG6000 in 5 days.Under 5%and 10%PEG treatmeant,the SOD activity,POD activity and chlorophyll content,soluble sugar content of all plants showed a downward trend,and the decline of wild type plants was more obvious.While the CAT activity of each plant was increased,and the transgenic plants was significantly increased.However,the amount of MDA and Pro in transgenic plants was lower than that in wild-type plants.As a result,the physiological indexes of transgenic plants were significantly changed,and the drought resistance was improved under 5%and 10%PEG treatmeant.While there was no significant difference between the transgenic and wild-type plants under 20%PEG treatment.