Overexpressed <i>BSR1</i>-Mediated Enhancement of Disease Resistance Depends on the MAMP-Recognition System

• Main Authors: Yasukazu Kanda, Yoko Nishizawa, Takashi Kamakura, Masaki Mori
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: International Journal of Molecular Sciences
• Subjects: disease resistance; microbe-associated molecular pattern (MAMP); <i>Pyricularia oryzae</i> (formerly <i>Magnaporthe oryzae</i>); <i>Oryza sativa</i> (rice); receptor-like cytoplasmic kinase (RLCK)
• Online Access: https://www.mdpi.com/1422-0067/21/15/5397
• ISSN: 1661-6596; 1422-0067

Plant plasma membrane-localized receptors recognize microbe-associated molecular patterns (MAMPs) and activate immune responses via various signaling pathways. Receptor-like cytoplasmic kinases (RLCKs) are considered key signaling factors in plant immunity. BROAD-SPECTRUM RESISTANCE 1 (BSR1), a rice RLCK, plays a significant role in disease resistance. Overexpression of <i>BSR1</i> confers strong resistance against fungal and bacterial pathogens. Our recent study revealed that MAMP-triggered immune responses are mediated by BSR1 in wild-type rice and are hyperactivated in <i>BSR1</i>-overexpressing rice. It was suggested that hyperactivated immune responses were responsible for the enhancement of broad-spectrum disease resistance; however, this remained to be experimentally validated. In this study, we verified the above hypothesis by disrupting the MAMP-recognition system in BSR1-overexpressing rice. To this end, we knocked out <i>OsCERK1</i>, which encodes a well-characterized MAMP-receptor-like protein kinase. In the background of BSR1 overaccumulation, the knockout of <i>OsCERK1</i> nearly abolished the enhancement of blast resistance. This finding indicates that overexpressed <i>BSR1</i>-mediated enhancement of disease resistance depends on the MAMP-triggered immune system, corroborating our previously suggested model.