대부분의 열대 식물은 chilling에 민감하게 반응한다. 대표적 열대 식물인 벼 잎에 대한 light-chilling 처리와 이 후의 회복기(post-chilling) 동안 일어나는 반응들을 알아보았다. Chilling 시 벼 잎에서의 광합성 효율($F_v/F_m$)은 대조구보다 50% 감소하였고, 상대적으로 $H_2O_2$ 양은 48% 증가하였다. 항산화 효소들 중 SOD와 GR 활성은 chilling과 post-chilling 시 증가하였다. 특히 SOD isoforms의 경우 CuZn-SOD와 Mn-SOD 가 발현된 반면 Fe-SOD는 발현되지 않았다. CAT 활성은 chilling 시 감소하였으며, 반면에 APX는 크게 증가하였다. Chilling 시 CAT의 isoforms의 변화를 보면, CAT-2와 -3의 활성이 감소한 것과 대조적으로 post-chilling 시 이들 isoforms의 활성은 증가하였다. 이처럼 APX와 CAT 활성은 벼 잎이 chilling stress를 겪게 될 때 상반되는 변화를 보여주었다.
We investigated photooxidation and responses of antioxidant enzymes involved in scavenging reactive oxygen species (ROS) after light-chilling ($4^{circ}C$) for 2 days and post chilling ($25^{circ}C$) in rice leaves. Chilling leaves indicated a 50% reduction in photosynthetic efficiency ($F_v/F_m$ ratio) and a 48% increase of $H_2O_2$, respectively, compared to the control group. In comparison with the control, activities of superoxide dismutase (SOD) and glutathione reductase (GR) increased at light-chilling and post-chilling. CuZn-SOD and Mn-SOD among SOD forms were detected in rice leaves, while Fe-SOD was not found. The increase of SOD and GR activity may serve as a basis for defense against chilling injury as it dismutase superoxide generated by light-chilling. Catalase (CAT) activity decreased during light-chilling, while activity of APX showed remarkable increase during light-chilling in rice leaves. Among CAT isoforms analyzed by 10% native PAGE, activities of isoform -2 and -3 were inhibited during light-chilling. From the elevated APX activity and decreased CAT activity, we suggest that these two enzymes show mutual supplementary relationships, indicating different tendency during light-chilling.
