LYCOPENE β-CYCLASE overexpression improves growth, modulates hormone content, and affects rhizospheric interactions in tobacco and tomato roots

: Expression of plant LYCOPENE β-CYCLASEs modulates abscisic acid and strigolactone contents resulting in enhanced root length, impaired mycorrhiza colonization frequency, and reduced Striga-seed germination in tobacco and tomato. Genetic engineering of the carotenoid biosynthesis made possible the biofortification of many crops by enhancing the provitamin A content in their edible parts. Recent studies showed that overexpression of a single carotenogenic gene, the LYCOPENE β-CYCLASE (LCYB), impacted plant architecture, and improved photosynthesis efficiency and stress tolerance in tobacco (Nicotiana tabacum cv. Xanthi) and tomato (Solanum lycopersicum). Here, we show that LCYB overexpression also enhanced root growth and biomass, and affected rhizospheric interactions, causing a reduction in mycorrhization and decreased capability to induce seed germination in root parasitic plants. These below-ground effects in tobacco and tomato are associated with changes in the levels of carotenoids, apocarotenoids, and phytohormones. Our findings highlight LCYB as a key regulatory and metabolic hotspot in the carotenoid pathway. Its overexpression induces profound changes in root architecture and below-ground interactions. These results lay the foundation for a new generation of crops that can better face the future environmental stress caused by global warming and show increased resistance to root parasitic plants.