Ruan, B.^, Hua, Z.^, Zhao, J.^, Zhang, B., Ren, D., Liu, C., Yang, S., Zhang, A., Jiang, H., Yu, H., Hu, J., Zhu, L., Chen, G., Shen, L., Dong, G., Zhang, G., Zeng, D., Guo, L., Qian, Q., and Gao, Z. (^ Co-first author)

Abstract

ATP-citrate lyases (ACL) play critical roles in tumour cell propagation, foetal development and growth, and histone acetylation in human and animals. Here, we report a novel function of ACL in cell death‐mediated pathogen defence responses in rice. Using ethyl methanesulphonate (EMS) mutagenesis and map‐based cloning, we identified an Oryza sativa ACL-A2 mutant allele, termed spotted leaf 30-1 (spl30-1), in which an A-to-T transversion converts an Asn at position 343 to a Tyr (N343Y), causing a recessive mutation that led to a lesion mimic phenotype. Compared to wild-type plants, spl30-1 significantly reduces ACL enzymatic activity, accumulates high reactive oxygen species and increases degradation rate of nuclear deoxyribonucleic acids. CRISPR/Cas9-mediated insertion/deletion mutation analysis and complementation assay confirmed that the phenotype of spl30-1 resulted from the defective function of OsACL-A2 protein. We further biochemically identified that the N343Y mutation caused a significant degradation of SPL30^N343Y in a ubiquitin‐26S proteasome system (UPS)-dependent manner without alteration in transcripts of OsACL-A2 in spl30-1. Transcriptome analysis identified a number of up‐regulated genes associated with pathogen defence responses in recessive mutants of OsACL-A2, implying its role in innate immunity. Suppressor mutant screen suggested that OsSL, which encodes a P450 monooxygenase protein, acted as a downstream key regulator in spl30-1 mediated pathogen defense responses. Taken together, our study discovered a novel role of OsACL-A2 in negatively regulating innate immune responses in rice.