Abstract:The lesion mimic mutant Jiazhe DB was obtained from the M2 population of Jiazhe B irradiated with γ-rays. To reveal the genetic and biological basis of the lesion mimic trait, the underlying mutant gene was mapped and the propertied and characters of chloroplast were investigated. Jiazhe DB is a typical Sekiguchi mutant, of which yellow-brown lesions appear spontaneously without pathogen attack during growth. The lesion spots expand in size until scattering over the whole surface of leaves. Chloroplasts started to degrade in mutant leaves before lesions became visible, resulting in lower photosynthetic efficiency. The lesion mimic trait is highly likely controlled by a recessive mutant allele of LOC_Os12g16720 of which the 1 425th guanine of is deleted and hence would result in frame shift and a truncated protein in Jiazhe DB. The transcription levels of four chloroplast-localized APXs (Ascorbate peroxidases) increased significantly in the mutant at daytime, but not at night time. The early degradation of chloroplasts and elevated levels of ROS (Reactive oxygen species) might have triggered the programmed cell death in Jiazhe DB. These results provided an important clue for further investigating and understanding the molecular mechanism of the occurrence of sekiguch lesion mimic.