Analysis On The Physiological And Biochemical Phenotype Of Arabidopsis Ethylene Biosynthesis Mutant In Response To Salt Stress

Ethylene plays an important role in plant growth and development and in responses to various stresses. However, it remains to clarify whether and how ethylene biosynthesis and signal transduction are invovled in response to salt stress.Ethylene synthase (ACC synthase, ACS) gene family have 12 member, we selected one of them,which named AtESTH (Arabidopsis thaliana gene for Ethylene Synthesis factor, AtESTH) to study wether response to salt stress. 150mM NaCl treatment for 5 days,germination rate of WT is about 7% , and Atesth germination rate is 15%, which is 2-times as much as WT; 150mM NaCl treatment for 10 days, the average root length of WT is 0.35±0.06 cm, and the average root length of Atesth is 0.95±0.03 cm, which the latter is nearly 3-times as much as the former. The RT-PCR results show that Atesth expression significantly increased compared with the control under the treatment of 150mM NaCl, indicating that AtESTH is involved in the response of Arabidopsis to salt stress at the transcriptional level.H⁺-ATP play an important role in keeping ion balance of plant cells. Experiment results show that the H⁺-ATP enzyme activity is similar between WT and Atesth under the control conditions. But treatment with 150mM NaCl for 72 hours, H⁺-ATP enzyme activity of Atesth significantly increased comparing to WT, indicating that H⁺-ATP activity changes in the Atesth plants salt stress of the adjustment process. 150 mM NaCl induce the fluorescence intensity of pH probe increased in Atesth mutant root cells comparing to that in WT by Confocal recording with the result of WT is raise 11% so the Atesth is 33%. This shows that AtESTH affect Arabidopsis tolerence to salt stress by regulating H⁺-ATPase activity and cellular pH.Under normal circumstances, plants maintain a certain level of intracellular ROS (Reactive oxygen species, ROS). But ROS levels in plant cells increased rapidly in response to stresses. By DAB staining and the treatment with 150mM NaCl for 4 hours, ROS levels of Atesth mutants did not significantly change comparing to that of WT. The Confocal recording show that WT is 4-times than it not treat by 150 mM NaCl,and the Atesth isnot change. Moreover, NaCl treatment increased CAT activity in WT(51%)or Atesth (114% )plants, indicating that AtESTH participate in ROS metabolism in response to salt stress.Ca²⁺ increased in a short time with the result of that WT increased 70% and Atesth increased 100%.suggesting that AtESTH might promote cytoplasma free Ca²⁺ to decrease absorb of the Na+ to response to salt stress.In summary, AtESTH might improve the adaptability of plants to salt stresss by adjusting the H⁺-ATPase activity and ROS metabolism .