Response of Monodehydroascorbate Reductase (MDHAR) in Lettuce (Lactuca sativa L.) Leaves Subjected to Water Deficit Stress
2008
Kang, S.J. (Kyungpook National University, Sangju, Republic of Korea), E-mail: [email protected]
The relationship between water deficit stress and monodehydroascorbate reductase (MDHAR) activity was determined in lettuce (Lactuca sativa L.) leaves under water stress condition imposed by with-holding water for 72 hrs. Relative water content determined in water deficit stressed lettuce leaves gradually reduced from 91.29% to 74.58%, and water content of medium drastically decreased 4.73% after quitting of irrigation. Hydrogen peroxide content in leaves subjected to water deficit stress rapidly increased, but soluble protein content rapidly decreased when those were compared to control plant. The relationship between relative water content and hydrogen peroxide content in stressed leaves positively correlated with R²=0.8851, but soluble protein content reversely correlated with R²=0.9826. Total chlorophyll content in stressed plant leaves was higher than that of control plant, and increased rapidly in early stage of treatment of both stressed and control plants. Carotenoid content was higher than that of control plant, and the ratio of carotenoid to total chlorophyll in stressed plant was higher as compared to control plant. As water deficit stress continued progressively, total ascorbate content in stressed plant leaves was a little higher than that of control plant. But dehydroascorbate (DHA) content within 6 hr of water deficit stress was higher than that of control plant, and then, content of control plant in 12 hr of stress treatment higher than that of stressed leaves. The activity of monodehydroascorbate reductase of cytosolic and chloroplastic tractions increased dramatically, and mRNA of MDHAR was highly detected by probing ∨32P-labeled single stranded MDHAR RNA of lettuce plant leaves subjected to water deficit stress. Relationship between MDHAR activity and relative water content and hydrogen peroxide highly correlated with R²=0.9937 and 0.8645, respectively.
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