Gn1a rice promotes symbiotic fish growth via reprogramming soil microbiome

Rice-fish symbiotic ecosystems significantly contribute to world food supply. Mutation in rice (Oryza sativa) quantitative trait locus Gn1a, encoding a cytokinin oxidase/dehydrogenase (OsCKX2), leads to cytokinin accumulation in plant, which promotes tillering and panicle branching to achieved higher yield and also shows a selective effect on soil microbial composition. Given that the growth of aquatic animals can be shaped by their surrounding microbial communities, we asked whether adjusting rice cytokinin levels might synergistically boosts both rice yield and fish growth. Herein, we co-cultured common carp (Cyprinus carpio) with ckx2 rice plants to determine the effect of cytokinins on fish. Surprisingly, compared to wild-type plants, the ckx2 plants enhanced nearly 10% fish growth and improved fish antibacterial capacity against Aeromonas hydrophila and Edwardsiella tarda. In fact, the growth-promoting effect on fish requires mediation by the soil microbiota. Mechanistically, ckx2 plants secreted more cytokinins into soil to reprogram the microbial composition, which subsequently translocated to fish gut and modulated the keystone microbes in gut to facilitate short-chain fatty acid production and carbohydrate degradation. These findings provide the first evidence that rice-derived cytokinins exert a cross-kingdom growth-promoting effect on fish, providing a boosting dual-production strategy for advancing rice-fish symbiotic ecosystem.