H₂O₂ Induces Association of RCA with the Thylakoid Membrane to Enhance Resistance of <i>Oryza meyeriana</i> to <i>Xanthomonas oryzae</i> pv. <i>oryzae</i>

• Main Authors: Qiong Mei, Yong Yang, Shenhai Ye, Weifang Liang, Xuming Wang, Jie Zhou, Chulang Yu, Chengqi Yan, Jianping Chen
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Plants
• Subjects: H₂O₂; Rubisco activase; thylakoid membrane; chloroplast stoma; <i>Xanthomonas oryzae</i> pv. <i>oryzae</i>; <i>Oryza meyeriana</i>
• Online Access: https://www.mdpi.com/2223-7747/8/9/351

<i>Oryza meyeriana</i> is a wild species of rice with high resistance to <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> (<i>Xoo</i>), 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 <i>Xoo</i> infection induced the relocation of RCA from the chloroplast stroma to the thylakoid membrane in <i>O. meyeriana</i>, but the underlying regulating mechanism and physiological significance of this association remains unknown. In this study, &#8220;H₂O₂ burst&#8221; with rapid and large increase in the amount of H₂O₂ was found to be induced by <i>Xoo</i> invasion in the leaves of <i>O.</i> <i>meyeriana</i>. 3, 3-diaminobenzidine (DAB) and oxidative 2, 7-Dichlorodi-hydrofluorescein diacetate (H₂DCFDA) staining experiments both showed that H₂O₂ was generated in the chloroplast of <i>O.</i> <i>meyeriana</i>, and that this H₂O₂ generation as well as <i>Xoo</i> 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 <i>O. meyeriana</i> 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 <i>O. meyeriana</i> to <i>Xoo</i>.