Editing of rice PSEUDO-ETIOLATION IN LIGHT microProtein genes promotes chloroplast development

Abstract The rice (Oryza sativa) PSEUDO-ETIOLATION IN LIGHT (OsPEL) microProtein family members function as dominant-negative regulators of chloroplast development and are conserved among land plants. Knockout of all three OsPEL genes enhanced plant greening traits and was accompanied by leaf anatomical modifications associated with chloroplast-enriched bundle sheath cells in rice. These phenotypic changes correlated with increased CO2 assimilation efficiency and yield. OsPEL1 specifically interacts with key positive regulators of photosynthesis, the rice GOLDEN2-LIKE (OsGLK) transcription factors and the PHOTOSYSTEM I ASSEMBLY 2 (OsPSA2) chaperone. OsPEL1 inhibits these regulators by sequestering OsGLK1 and OsPSA2 in the cytoplasm, which prevents their proper localization to the nucleus and chloroplast, respectively. Supported by RNA-seq evidence of transcriptional homeostasis in greening-related genes, we reveal a multilayered regulatory mechanism and identify the OsPEL family as a promising target for crop improvement.