Enhanced reactive oxygen species scavenging by overproduction of superoxide dismutase and catalase delays postharvest physiological deterioration of cassava storage roots.
Postharvest physiological deterioration (PPD) of cassava (Manihot esculenta) storage roots is the result of a rapid oxidative burst, which leads to discoloration of the vascular tissues due to the oxidation of phenolic compounds. In this study, coexpression of the reactive oxygen species (ROS)-scavenging enzymes copper/zinc superoxide dismutase (MeCu/ZnSOD) and catalase (MeCAT1) in transgenic cassava was used to explore the intrinsic relationship between ROS scavenging and PPD occurrence. Transgenic cassava plants integrated with the expression cassette p54::MeCu/ZnSOD-35S::MeCAT1 were confirmed by Southern-blot analysis. The expression of MeCu/ZnSOD and MeCAT1 was verified by quantitative reverse transcription-polymerase chain reaction and enzymatic activity analysis both in the leaves and storage roots. Under exposure to the ROS-generating reagent methyl viologen or to hydrogen peroxide (H2O2), the transgenic plants showed higher enzymatic activities of SOD and CAT than the wild-type plants. Levels of malondialdehyde, chlorophyll degradation, lipid peroxidation, and H2O2 accumulation were dramatically reduced in the transgenic lines compared with the wild type. After harvest, the storage roots of transgenic cassava lines show a delay in their PPD response of at least 10 d, accompanied by less mitochondrial oxidation and H2O2 accumulation, compared with those of the wild type. We hypothesize that this is due to the combined ectopic expression of Cu/ZnSOD and CAT leading to an improved synergistic ROS-scavenging capacity of the roots. Our study not only sheds light on the mechanism of the PPD process but also develops an effective approach for delaying the occurrence of PPD in cassava.
National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research , Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Jia
J
Xu
Xiaoguang
X
Duan
Jun
J
Yang
John R
JR
Beeching
Peng
P
Zhang
D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics; D002374:Catalase / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D016166:Free Radical Scavengers / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D002365:Manihot / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D018384:Oxidative Stress / Q000187:drug effects; D010269:Paraquat / Q000494:pharmacology; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D030821:Plants, Genetically Modified; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
D016166:Free Radical Scavengers; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D010269:Paraquat