• antioxidant
• flavonoid
• microarray analysis
• photomorphogenesis
• phytochrome
• UV-B radiations

ABSTRACT

Flavonoids and phenolic acids have many functions in plants and they also have a antioxidative and anticarcinogenic effects in humans. Stress conditions such as excessive UV light, wounding or infection induces the biosynthesis of phenolic compounds. Light is one of the most extensively studied environmental factors in the phenolic metabolism. It is thought that phenolic compounds help to attenuate the amount of light reaching the photosynthetic cells.
It’s well established that photomorphogenic response are regulated from a complex interactions within a network of phytochrome, cryptochrome and UV-B phototransduction pathways in seedlings, on the other hand no information are available on the role of this interactions for accumulation of flavonoid and phenolic acids in tomato fruits.
In the present research tomato photomorphogenic mutants were used under different light conditions to investigate the phytochrome interaction on the photomorphogenic response and on the content of antioxitants and phenolics compounds.
In tomato seedlings the hypocotyls length were significantly inhibited by the UV-B radiations and the phyB1 showed a negative regulation of stem elongation. For a maximal flavonoids /anthocyanin accumulation under UV-B in seedlings phyB1 were required instead phyB2 acted as a negative regulator of the UV-B signaling in fact in phyB2 mutants responses were very little and they were minimized in the absence of all 3 major phytochrome.
The inhibition of hypocotyl elongation in wild-type tomato was significantly registered only in WG 280-filtered UV radiations but the active spectral range for the antioxidants content was between 280-305 nm all the UB-B spectral range.
The fruits antioxidants content was conditioned by genotype and environment interaction. The PHY mutants showed the smallest responses and the phyB1 played a central role for the correct accumulation of these compounds.
Furthermore a microarray-based expression profiling was used to identify the regulated by the UV-B radiations in tomato fruits.
Differentially expressed gene were identified in WT and phyB1 mutants and grouped in functional category. In each genotypes there were several answers and genes expression showed the complexity of the UV-B regulation transduction.