Abstract
Oryza meyeriana is a wild species of rice with high resistance to Xanthomonas oryzae pv. oryzae (Xoo), but the detailed resistance mechanism is unclear. Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) activase (RCA) is an important enzyme that regulates photosynthesis by activating Rubisco. We have previously reported that Xoo infection induced the relocation of RCA from the chloroplast stroma to the thylakoid membrane in O. meyeriana, but the underlying regulating mechanism and physiological significance of this association remains unknown. In this study, “H2O2 burst” with rapid and large increase in the amount of H2O2 was found to be induced by Xoo invasion in the leaves of O. meyeriana. 3, 3-diaminobenzidine (DAB) and oxidative 2, 7-Dichlorodi-hydrofluorescein diacetate (H2DCFDA) staining experiments both showed that H2O2 was generated in the chloroplast of O. meyeriana, and that this H2O2 generation as well as Xoo resistance of the wild rice were dramatically dependent on light. H2O2, methyl viologen with light, and the xanthine-xanthine oxidase system all induced RCA to associate with the thylakoid membrane in vitro, which showed that H2O2 could induce the relocation of RCA. In vitro experiments also showed that H2O2 induced changes in both the RCA and thylakoid membrane that were required for them to associate and that this association only occurred in O. meyeriana and not in the susceptible cultivated rice. These results suggest that the association of RCA with the thylakoid membrane helps to protect the thylakoid membrane against oxidative damage from H2O2. Therefore, in addition to its universal function of activating Rubisco, RCA appears to play a novel role in the resistance of O. meyeriana to Xoo.
Highlights
Rice (Oryza sativa L.) is a primary staple cereal and a source of food for more than half of the world’s population, but it is susceptible to many pathogens that can dramatically decrease yields
We have reported that the inoculation of O. meyeriana with Xanthomonas oryzae pv. oryzae (Xoo) induced the relocation of Rubisco activase (RCA) from the chloroplast stroma to associate with the thylakoid membrane [14]
We suggest that the association of RCA with the thylakoid membrane helps to protect the thylakoid membrane against oxidative damage by H2 O2
Summary
Rice (Oryza sativa L.) is a primary staple cereal and a source of food for more than half of the world’s population, but it is susceptible to many pathogens that can dramatically decrease yields. Plants 2019, 8, 351 diseases in all the major rice growing countries, typically reducing yields by 20% to 30%, but by as much as 50% in years when the disease is prevalent [1,2,3,4] Chemical control of this disease is temporarily effective, but it often causes environmental pollution, and the most effective method of control is generally recognized to be through the use of resistant cultivars. It is difficult for plant breeders to find new resistance genes from within the currently narrow genetic base of rice cultivars They have low grain yields, wild species of the genus Oryza have adapted through natural selection to survive in harsh environments, and often possess many useful traits that are not present in cultivated rice, including high disease resistance. Many wild species are highly resistant to bacterial blight, including O. longistaminata [5], O. minuta [6], O. rufipogon [7], and
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