Suchergebnisse

The aim of this study was to investigate the role of tocopherols in the susceptibility of Star Ruby grapefruit to postharvest chilling injury (CI). Fruit exposed to normal sunlight (NC, non-covered) and deprived of light (C, covered) in the last stages of development were used. Tocopherol contents increased in the flavedo of both NC and C fruit during development, concomitantly with the up-regulation of TAT1 and most genes of the tocopherol-core pathway. Fruit shading reduced total contents by repressing γ-tocopherol accumulation, associated to a down-regulation of GGDR and VTE1 and, to a lesser extent, of VTE2, VTE3a and VTE4. During cold storage, total and α-tocopherol contents increased in NC and C fruit, and no direct relationship between tocopherol accumulation and CI tolerance was found. Cold stress up-regulated most genes involved in the synthesis of tocopherol precursors and down-regulated those of the tocopherol-core pathway, but changes seemed to be cold-mediated and not related to CI development. ; This work was supported by research grants RTI2018-095131-B-I00 of the Ministry of Science and Innovation (Spanish Government). F. Rey is the recipient of a PhD scholarship (POS_EXT_2016_1_133720) from ANII (Uruguay). ; Peer reviewed

[EN] 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. ; We greatly thank Juan Antonio Lopez-Raez for providing cDNA samples of nonmycorrhized and mycorrhized tomato roots; Ernesto Llamas for providing the pGWB417_AtPRK construct, and Albert Ferrer and Laura Gutierrez for the pDE-Cas9 (with kanamycin resistance) plasmid. The technical support of M. Rosa Rodriguez-Goberna and all CRAG services is also appreciated. This work was funded by the European Regional Development Fund (FEDER) and the Spanish Agencia Estatal de Investigacion (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) ...