Engineering the polyphenolic biosynthetic pathway stimulates metabolic and molecular changes during fruit ripening in “Bronze” tomato

Abstract

The metabolic engineered Bronze tomato line is characterized by the constitutive over-expression of the VvStSy gene encoding a structural protein responsible for the stilbenoids biosynthesis and the fruit-specific over-expression of AmDel/Rosea1 and AtMYB12 genes encoding transcription factors that activate the polyphenol biosynthetic pathway. This tomato line is known for the increased levels of polyphenols in ripe fruits and for beneficial health promoting antioxidant and anti-inflammatory effects. In this study we analyzed the transcriptional and metabolic profiling in mature green, breaker, orange and ripe fruits compared to the normal tomato counterparts during ripening, to unravel the effect of regulatory and structural transgenes on metabolic fluxes of primary and secondary metabolisms. Our results showed that the shikimate synthase (SK) gene was up-regulated in the Bronze fruit, and the transcriptional activation is consistent with the metabolic changes observed throughout fruit ripening. These results paralleled with a reduced level of simple sugars and malate, highlighting the consumption of primary metabolites to favor secondary metabolites production and accumulation. Finally, carotenoids quantification revealed a change in the lycopene/β-carotene ratio in the Bronze fruit as a consequence of significant lower level of the first and higher levels of the latter. The high polyphenols and /β-carotene content displayed by the Bronze fruit at the later stages of fruit ripening renders this line an interesting model to study the additive or synergic effects of these phyto-chemicals in the prevention of human pathologies.

CRISPR/Cas9-mediated SNAC9 mutants reveal the positive regulation of tomato ripening by SNAC9 and the mechanism of carotenoid metabolism regulation

“…With the increase in fruit maturity, carbohydrates, cellulose, pectin, and other substances in the fruit were hydrolyzed continuously, and the total amount of respiration metabolism was less than the total amount of degradation, increasing the solid soluble content [ 24 , 32 ]. WT reached its maximum value in the B + 6 period, reaching 3.03 Brix% ( Fig.…”

Targeted approaches to improve tomato fruit taste

“…In tomato fruit ( S. lycopersicum ), malic acid, citric acid, ascorbic acid, tartaric acid, and glutamic acid are the major organic acids, of which malic acid and citric acid are the predominant compounds affecting fruit flavor and palatability [ 34 , 35 ]. Citric acid is the dominant organic acid at all stages of the tomato fruit life cycle, while malic acid is present at considerable levels in unripe green tomato fruits, and the malic acid content subsequently declines while fruits ripen [ 29 , 36 ].…”

“…The changes in sugar and organic acid contents of tomato fruits are closely related to the ripeness of tomato fruits at different developmental stages [ 29 ]. The total content of sugar metabolites increases by 4% during ripening, with glucose mainly present in immature green fruits early in development, while fructose contents are usually higher than glucose contents in fully ripe fruits [ 32 , 35 ]. However, after fruit ripening the total content of all sugar metabolites decreases [ 41 ].…”

Beneficios de los alimentos transgénicos biofortificados, una revisión del 2012 al 2022

“…El alto contenido de carotenoide total y astaxantina se ha mejorado en el tomate mediante la expresión del betacaroteno cetolasa e hidroxilasa (Huang et al, 2013). Para mejorar el contenido de carotenoides del fruto del tomate, el gen Psy-1 se expresa de forma constitutiva en el tomate, es la enzima psy-1 la que cataliza el paso preliminar comprometido de la biosíntesis de la ruta de los carotenoides al producir fitona a partir de difosfato de geranilgeranilo [GGPP] (Scarano et al, 2022). En hojas y frutos de tomate recientemente se informó de la biofortificación de yodo mediante la expresión de los genes HMT, S3H y SAMT (Halka et al, 2019).…”