A Novel Allele Encoding 7-Hydroxymethyl Chlorophyll a Reductase Confers Bacterial Blight Resistance in Rice.

Rice spotted leaf mutants are helpful to investigate programmed cell death (PCD) and defense response pathways in plants. Using a map-based cloning strategy, we characterized novel rice spotted leaf mutation that encodes a 7-hydroxymethyl chlorophyll a reductase (). The wild-type (WT) allele could rescue the mutant phenotype, as evidenced by complementation analysis. was constitutively expressed at all rice tissues tested and its expression products localized to chloroplasts. The mutant exhibited PCD and leaf senescence with increased HO (hydrogen peroxide) accumulation, increased of ROS (reactive oxygen species) scavenging enzymes activities and TUNEL (terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling) -positive nuclei, upregulation of PCD related genes, decreased chlorophyll (Chl) contents, downregulation of photosynthesis-related genes, and upregulation of senescence-associated genes. Besides, the mutant exhibited enhanced bacterial blight resistance with significant upregulation of defense response genes. Knockout lines of exhibited spotted leaf phenotype, cell death, leaf senescence, and showed increased resistance to the bacterial pathogen pv.   coupled with upregulation of five pathogenesis-related marker genes. The overexpression of resulted in increased susceptibility to with decreased expression of pathogenesis-related marker genes. Altogether, our findings revealed that is involved in regulating cell death and defense response against bacterial blight pathogen in rice.