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Overexpression of hyperactive mutant forms of phytochromes B1 and B2 as a means of manipulating tomato quality traits

Grant number: 18/25774-2
Support Opportunities:Scholarships in Brazil - Master
Effective date (Start): May 01, 2019
Effective date (End): June 30, 2021
Field of knowledge:Biological Sciences - Botany - Pant Physiology
Principal Investigator:Luciano Freschi
Grantee:Scarlet Santos Monteiro
Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:16/01128-9 - Light and hormonal regulation of nutritional quality in Solanum lycopersicum, AP.TEM


Fleshy fruit growth, maturation, and ripening are under strict developmental, hormonal, and epigenetic regulation, which in turn are fine-tuned by a plethora of environmental stimuli. Among environmental cues, light plays a significant role in determining fruit growth, pigmentation, and timing of ripening. In tomato (Solanum lycopersicum), a major crop and important model species for fleshy fruits, reports indicate that changes in phytochrome (PHY)-dependent light perception can lead to significant alterations in fruit development and quality traits. However, most of these studies have focused on PHY-deficient mutants, whose changes in fruit physiology were associated with pleiotropic disturbs associated with the constitutive PHY deficiency. Taking into consideration the recent discovery in Arabidopsis thaliana that a mutation of the tyrosine residue to a histidine at position 276 of PHYB results in permanent activation of the photoreceptor regardless of the light conditions, this project aims to explore the biotechnological potential of this manipulation of photoperception in tomato plants. In tomato, SlPHYB1 and SlPHYB2 paralogous, which originated during the Solanum whole-genome triplication event, seem to have suffered functional diversification; therefore, the impact of the overexpression of hyperactive mutant forms of each of these paralogs (SlPHYB1Y253H e SlPHYB2Y252H) on fruit physiology and nutritional content will be analyzed via biochemical and molecular biology approaches. Two promoters will be employed to drive the transgene overexpression, one constitutive (35S) and another fruit-specific (PPC2). This will allow us to determine which of these overexpression strategies would hold higher biotechnological potential, leading to increased fruit nutritional quality with minimal collateral effects on plant productivity. Multiple quality traits will be monitored in the transgenic fruits, including antioxidant analysis and carotenoid, flavonoid, tocopherol, organic acid, sugar and aminoacid profile. In addition, the impact of the genetic manipulations on plastid abundance, size and ultrastructure will also be analyzed, once chloroplasts and chromoplasts play a central role on the metabolism and storage of many of these nutraceutical compounds. Moreover, the transcriptional profile of genes related to the metabolism of these compounds will also be characterized whenever significative changes in the content of these metabolites were detected in the transgenic lines. Productivity index and ripening progression will also be monitored in the lines displaying the highest changes in fruit nutritional content. Altogether, the approaches included in this project may contribute for determining the biotechnological potential of using engineered PHY versions as a photobiotecnological strategy to improve tomato fruit nutritional quality, and may also allow identifying the physiological processes regulated by SlPHYB1 and SlPHYB2 paralogous both within the fruit (fruit-specific manipulation) and the whole-plant context (constitutive manipulation). (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
RODRIGUES ALVES, FREDERICO ROCHA; LIRA, BRUNO SILVESTRE; PIKART, FILIPE CHRISTIAN; MONTEIRO, SCARLET SANTOS; FURLAN, CLAUDIA MARIA; PURGATTO, EDUARDO; PASCOAL, GRAZIELI BENEDETTI; SILVA ANDRADE, SONIA CRISTINA; DEMARCO, DIEGO; ROSSI, MAGDALENA; et al. Beyond the limits of photoperception: constitutively active PHYTOCHROME B2 overexpression as a means of improving fruit nutritional quality in tomato. Plant Biotechnology Journal, v. 18, n. 10, . (16/04924-0, 18/25774-2, 18/16389-8, 16/01128-9)
Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
MONTEIRO, Scarlet Santos. Constitutively active alleles of phytochromes B1 and B2 and their impacts on tomato vegetative and reproductive development. 2022. Master's Dissertation - Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) São Paulo.

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