Phytochrome manipulation as a biofortification strategy of tomato fruits (Solanum lycopersicum L.)

Manipulation of light signaling pathway components has been widely applied as a molecular plant breeding strategy in crop species. Phytochromes (PHYs), red/far-red photoreceptors, play central roles concerning light signal transduction, controlling a plethora of physiological processes in fruits, including the biosynthesis of compounds with nutritional value. However, information regarding the applicability of PHY manipulation as a photobiotechnological tool aiming fruit biofortification are limited. In the present thesis, the impacts of fruit-specific overexpression of PHYTOCHROME B2 (PHYB2) and a mutated constitutively active form of this photoreceptor (PHYB2Y252H) on tomato fruit development were evaluated. In green fruits, either PHYB2 or PHYB2Y252H overexpression increased plastid number and thylakoid development, boosting up the synthesis and storage capacities of important compounds with nutritional value. Accordingly, red ripe PHYB2Y252H-overexpressing fruits accumulated more carotenoids, vitamin E, flavonoids and vitamin C as a consequence of specific modulation of biosynthetic genes associated with the respective metabolic pathways throughout fruit development. Compared to the wildtype, transgenic fruits exhibited limited changes in primary metabolism, including increments and reductions in lipid and soluble sugar levels, respectively. Accumulation of antioxidant compounds was substantially intensified by PHYB2Y252H-overexpression compared to the native form PHYB2. Altogether, our findings indicate that PHY activity manipulation represents a relevant photobiotechnological tool for fleshy fruit biofortification (AU)