Response of Monodehydroascorbate Reductase in Lettuce Leaves Subjected to Low Temperature Stress

Abstract

The relationship between MDHA reductase activity and ascorbate, dehydroascorbate, and hydrogen peroxide content was evaluated, and this experiment was conducted to determine the change of MDHA reductase activity and the level of steady-state mRNA abundance of MDHA reductase in lettuce leaves subjected to low temperature stress. MDHA reductase activity of chloroplastic and cytosolic fraction in lettuce leaves subjected to 4℃ for 24 hr increased, followed by a steady decrease during the duration of recovery to 20℃ for 48 hr. The content of ascorbate slowly increased during low temperature treatment, followed by a rapid increase during the duration of recovery to 20℃ for 48 hr, while dehydroascorbate content rapidly decreased. The relationship between MDHA reductase activity of chloroplastic and cytosolic fraction in lettuce leaves subjected to 4℃ and ascorbate content correlated positively (R 2 =0.9240, 0.9108, respectively), but MDHA reductase activity of chloroplastic and cytosolic fraction and dehydroascorbate were reversely correlated (R 2 =0.8638, 0.8980, respectively). Hydrogen peroxide content and MDHA reductase activity of chloroplastic and cytosolic fraction in lettuce leaves subjected to 4℃ correlated positively (R 2 =0.9443, 0.9647, respectively). Northern blot analysis showed that the level of mRNA transcript of MDHA reductase was similar to total activity of MDHA reductase, and also that the level of mRNA of MDHA reductase after recovery to 20℃ for 24 hr decreased.

Relationship Between Relative Water Content and Ascorbate Redox Enzymes Activity in Lettuce Leaves Subjected to Soil Water Stress

“…(Conklin, 2001;Tokugana, et al, 2005 (Foyer and Halliwell, 1976;Foyer et al, 1983;Shigeoka et al, 2002 (Shigeoka et al, 2002;Shimaoka et al, 2000;Urano et al, 2000;Yoshimura et al, 2000). 이들 효소의 활성변화에 영향을 주는 인자로는 오존처리 , 관수온도 (Kang et al, 2001), 수분부족 (Kang, 2008) 등이 있으며, 시금치 (Morell et al, 1997), 완두콩 (Leterrier et al, 2005), 토마토 (Grantz et al, 1995) )를 측정하였 다 . DHAR (EC 1.8.5.1)의 활성도는 10 mM GSH, 5 mM DHA와 조효소액을 첨가한 50 mM .…”