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.

Center of Excellence for Sustainable Food Security KAUST 23955 6900 Thuwal Saudi Arabia

Departamento de Biología Facultad de Ciencias Centro de Biología Molecular Vegetal Universidad de Chile Las Palmeras Ñuñoa 3425 Santiago Chile

Department of Life Sciences and Systems Biology University of Torino 10125 Turin Italy

Laboratory of Growth Regulators Faculty of Science Palacký University and Institute of Experimental Botany The Czech Academy of Sciences Šlechtitelů 27 78371 Olomouc Czech Republic

Plant Science Program Biological and Environmental Science and Engineering Division King Abdullah University of Science and Technology 23955 6900 Thuwal Saudi Arabia

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