Several geranylgeranyl diphosphate synthase isoforms supply metabolic substrates for carotenoid biosynthesis in tomato

Geranylgeranyl diphosphate (GGPP) produced by GGPP synthase (GGPPS) serves as a precursor for many plastidial isoprenoids, including carotenoids. Phytoene synthase (PSY) converts GGPP into phytoene, the first committed intermediate of the carotenoid pathway.Here we used biochemical, molecular, and genetic tools to characterise the plastidial members of the GGPPS family in tomato (Solanum lycopersicum) and their interaction with PSY isoforms.The three tomato GGPPS isoforms found to localise in plastids (SlG1, 2 and 3) exhibit similar kinetic parameters. Gene expression analyses showed a preferential association of individual GGPPS and PSY isoforms when carotenoid biosynthesis was induced during root mycorrhization, seedling de-etiolation and fruit ripening. SlG2, but not SlG3, physically interacts with PSY proteins. By contrast, CRISPR-Cas9 mutants defective in SlG3 showed a stronger impact on carotenoid levels and derived metabolic, physiological and developmental phenotypes compared with those impaired in SlG2. Double mutants defective in both genes could not be rescued.Our work demonstrates that the bulk of GGPP production in tomato chloroplasts and chromoplasts relies on two cooperating GGPPS paralogues, unlike other plant species such as Arabidopsis thaliana, rice or pepper, which produce their essential plastidial isoprenoids using a single GGPPS isoform.This work was funded by the European Regional Development Fund (FEDER) and the Spanish Agencia Estatal de Investigación (grants BIO2017-84041-P and BIO2017-90877-REDT) and Generalitat de Catalunya (2017SGR-710) to MRC. Support by the collaborative European Union’s Horizon 2020 (EU-H2020) ERA-IB-2 (Industrial Biotechnology) BioProMo project to MRC (PCIN-2015-103), RK and JB (053-80-725) is also acknowledged. CRAG is financially supported by the Severo Ochoa Programme for Centres of Excellence in R&D 2016–2019 (SEV-2015-0533) and the Generalitat de Catalunya CERCA Programme. MVB was funded with a Spanish Ministry of Education, Culture and Sports PhD fellowship (FPU14/05142) and a EU-H2020 COST Action CA15136 (EuroCaroten) short-stay fellowship. ME is supported by a Spanish Agencia Estatal de Investigación (BES-2017-080652) PhD fellowship. IFS is supported by the EU-H2020 Marie S. Curie Action 753301 (Arcatom).Peer reviewe