关键词: 水稻（Oryza sativa L.）, 早衰, 基因定位, eslh1, ROS

Abstract: INTRODUCTION: Plant senescence is an orderly process of structural dismantling in plant tissues and organs, accompanied by coordinated nutrient recycling and redistribution, and is triggered by internal and external cues. It is strictly governed by a genetic program, and perturbation of any regulatory step can significantly impair plant growth and development.
RATIONALE: Identifying key genes that regulate crop senescence, elucidating their mechanisms, and applying these insights to breeding are critical for improving crop quality and yield. Here, we generated a genetically stable mutant, eslh1 (early senescence, late heading), via ethyl methanesulfonate (EMS)-mediated mutagenesis of the indica rice maintainer line Xinong 1B. We characterized eslh1 through agronomic trait evaluation, ultrastructural observation, photosynthetic performance assay, physiological measurements, and expression analysis of senescence-related genes. Candidate gene identification was achieved by gene mapping and sequencing.
RESULTS: Relative to the wild type (WT), eslh1 leaves displayed damaged chloroplasts, reduced chlorophyll content, and lower photosynthetic efficiency. Moreover, eslh1 had impaired reactive oxygen species (ROS) scavenging, leading to ROS accumulation, accelerated leaf senescence, and reduced yield. Expression analysis revealed downregulation of genes involved in photosynthetic pigment synthesis, photosystem subunits, senescence repression, and antioxidant defense, whereas genes linked to pigment degradation and senescence promotion were upregulated. Mapping localized the ESLH1 candidate to a 210.5-kb interval on chromosome 7. Sequencing identified a single-base mutation exclusively in the core MYB response element (MRE) of the Os07g0180300 promoter. Thus, Os07g0180300 was designated as the ESLH1 candidate, representing a novel senescence regulator in rice.
CONCLUSION: Collectively, eslh1 exhibits poor agronomic traits, disrupted chloroplast structure, reduced chlorophyll, impaired photosynthesis, ROS accumulation, diminished ROS scavenging, and aberrant expression of senescence-related genes. Os07g0180300 is the candidate gene underlying ESLH1.

Key words: rice (Oryza sativa L.),, early senescence,, gene mapping,, eslh1,, ROS