A cytochrome P450 involved in apocarotenoid signaling enhances plant photosynthetic capacity and photooxidative stress tolerance

β-cyclocitric acid and its precursor β-cyclocitral are signaling apocarotenoids which trigger defense and detoxification mechanisms enhancing plant tolerance to abiotic stresses. From a transcriptomic analysis of Arabidopsis plants exposed to each apocarotenoid over several exposure times, we identified a gene ( CYP81D11 ) encoding a cytochrome P450 that is strongly induced under all conditions and is under the control of the TGAII-SCL14 transcription regulator. Overexpressing the CYP81D11 gene in Arabidopsis led to a very tolerant phenotype to high light stress while a CYP81D11 - deficient mutant was photosensitive. The transcriptomic profile of the CYP81D11 overexpressor revealed a selective upregulation of genes related to photosynthesis and the response to high light stress. Photosynthetic electron transport, CO ₂ fixation and biomass production were noticeably improved by high expression levels of CYP81D11 . These effects occurred in high light, not in low light, and were associated with a noticeable reduction of singlet oxygen photoproduction. These findings indicate that CYP81D11 is a key component of β-cyclocitral-induced stress tolerance, acting through enhancement of the photosynthetic capacity of leaves. This gene could be a new target for improving photosynthesis, particularly in sunny environments.