Physiological Responses and Expression Profile of NADPH Oxidase in Rice (Oryza Sativa) Seedlings under Different Levels of Submergence

Abstract

Background: Flooding due to global climate change is a serious problem that frequently decreases crop yields. Rice fields in flood-prone areas often experience full or partial submergence. Submergence has an adverse effect on internal oxygen availability, sugar status and survival. Complete submergence imposes severe pressure on plants, principally because the excess water in their surroundings deprives them of certain basic resources such as oxygen, carbon dioxide and light for photosynthesis. To better understand the mechanisms involved under different levels of flooding, it is necessary to further observe physiological responses and to identify the Rboh genes involved and determine how they are regulated during submergence. Results: In this study, significant physiological changes were observed in plant height, leaf sheath elongation and chlorophyll a, b and total content under partial and full submergence treatments. Senescence-regulating genes were severely affected under full submergence. Additionally, intracellular oxidative homeostasis was disrupted by overproduction of H2O2 and O2−, which affected cell viability and antioxidant enzyme activity, under different levels of submergence. Quantitative RT-PCR analyses revealed that complex regulation of Rboh genes is involved under different levels of submergence. Conclusion: Our results demonstrated that the effect of physiological and the transcript levels of OsRboh genes were presented different responses to different levels of submergence in rice seedlings. There have different mechanism in intracellular to response different levels of submergence. Finally we discuss effects of the regulation of OsRboh expression and ROS production which was important to maintain homeostasis to help rice seedlings face different levels of submergence.