Physiological differences of three transgenic sweet potatoes in response to PEG-6000-imitated drought stress
Drought is an important factor affecting crop growth.The physiological response mechanism of three transgenic sweet potatoes to drought stress was elucidated through comprehensive comparison of their responses to drought stress,which laid a foundation for the subsequent cultivation of sweet potato varieties with strong drought resistance.Under 15%PEG-6000 simulated drought stress conditions,trans-genic lines of Cu/Zn SOD&APX gene driven by oxidation-induced promoter SWPA2,transgenic lines of Ib-MYB1 gene driven by tissue-specific promoter SPO,transgenic lines of IbOr gene driven by constitutive promoter CaMV 35S and their wild type controls were used as test materials,respectively.The changes of photosynthetic indexes and antioxidant enzymes of three transgenic sweet potatoes under drought stress were studied,and the drought resistance mechanism of three genes was clarified.The results indicate that,with the extension of stress time,the net photosynthetic rate(Pn),chlorophyll content and carotenoid content of the three sweet potato varieties continued to decrease,but the decrease of the three transgenic lines was less than that of the non-transgenic control,and the decrease of Cu/Zn SOD&APX gene sweet potato was the least.The anthocyanin content,H2O2 and MDA content of the three sweet potato varieties increased with the extension of stress time,but the increase of H2O2 and MDA contents of the transgenic line were less those that of the non-transgenic control,and the accumulation of anthocyanin in the trans-genic sweet potato with IbMYB1 gene was about 2.5 times of that before stress.After drought stress,the carotenoid content in sweet potato leaves decreased with the extension of stress time,and the carotenoid content of IbOr transgenic lines was significantly higher than that of the control.The activities of antioxi-dant enzymes(SOD,POD,APX,CAT)of sweet potato varieties increased firstly and then decreased with the extension of stress time,among which,the activity of antioxidant enzymes increased the most and the antioxidant capacity was the strongest in Cu/Zn SOD&APX transgenic lines.DPPH scavenging capacity of transgenic IbMYB1 sweet potato was maintained at a high level after drought stress,indicating strong non-enzymatic antioxidant capacity.The comprehensive analysis showed that Cu/Zn SOD&APX and Ib-MYB1 lines had the highest drought resistance,followed by IbMYB1 gene lines,and IbOr gene lines had a weak drought resistance.The Cu/Zn SOD&APX transgenic sweet potato could reduce oxidative damage through stronger antioxidant enzyme activity,thus maintaining higher chlorophyll content and carotenoid content,and thus maintaining higher net photosynthetic rate and improving drought resistance.Transgen-ic lines with IbMYB1 gene protected chloroplasts by increasing the content of anthocyanin,a non-enzymat-ic antioxidant,and strong DPPH scavenging ability,thus enhancing photosynthetic capacity and drought resistance.However,the IbOr transgenic lines could eliminate reactive oxygen species(ROS),protect chlo-roplast structure,reduce membrane lipid oxidation damage,and improve the resistance to drought stress through the accumulation of carotenoid content.
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维普
