OEE1 affects the tobacco photosynthesis through the hormone regulation

The Oxygen-Evolution Enhancer Protein 1 (OEE1), also known as Photosystem II Protein O (PsbO), is an important extrinsic subunit of photosystem II. However, understanding of the mechanism by which it affects plant growth and development in tobacco is limited. In this study, we first demonstrated that OEE1, which is mainly chloroplast-localized, was conserved in tobacco ( Nicotiana tabacum ) and expressed at high levels in leaves and leaf veins. The loss of function of OEE1 resulted in a defective plant growth phenotype, characterized by decreased plant height, narrower leaf angle and low photosynthetic efficiency. However, the overexpression line could complement this phenotype. Subsequent transcriptome analysis revealed differentially expressed genes (DEGs) in WT plants and oee1 mutants, with DEGs being enriched in cellular, hormone metabolic and photosynthetic pathways. Further analysis confirmed that the contents of endogenous hormones and chemical compositions, including amino acids, sugars, polyphenols and organic acids, were changed in the absence of OEE1 . In conclusion, the results demonstrate that OEE1 regulates the photosynthesis pathway, which affects the endogenous metabolites and plant growth/development in a hormone-dependent manner in tobacco. • CRISPR/Cas9-mediated oee1 mutant is defect in plant growth and development. • OEE1 is highly expressed in leaf tissues and required for the photosynthesis. • Transcriptome analysis displays the changes of the cellular hormone level and endogenous metabolites. • OEE1 affects the plant phenotype, probably dependent on hormone pathway.