Response of wild-type and high pigment-1 tomato fruit to UV-B depletion: flavonoid profiling and gene expression

Abstract

The tomato high pigment-1 (hp-1) mutant is characterised by exaggerated photoresponsiveness and increased fruit pigmentation, and carries a mutation in the HP1/LeDDB1 gene, encoding the tomato homologue of the negative regulator of the light signal transduction DDB1a from Arabidopsis. Here, we investigated the molecular events underlying flavonoid accumulation in flesh and peel of wild-type and hp-1 fruits in presence or absence of UV-B light. In hp-1 peel, a twofold higher level of rutin and an earlier accumulation of flavonoids than in wild-type were observed, which correlated to the earlier activation of most flavonoid biosynthetic genes compared to wild-type. In hp-1 flesh, flavonoid content was up to 8.5-fold higher than in wild-type and correlated to the higher transcript level of flavonoid genes compared to wild-type. In both tissues, the expression of flavonoid genes was correlated with the anticipated and/or enhanced activation of the light signal transduction genes: LeCOP1LIKE, LeCOP1 and LeHY5. In wild-type, flavonoid content was severely reduced by UV-B depletion mostly in peel, whereas in hp-1 it was significantly increased in flesh. The activation of flavonoid and light signal transduction genes was UV-B dependent mostly at the mature green stage, whereas LeDDB1 expression was not regulated by UV-B.

Application of supplemental UV‐B radiation in pre‐harvest to enhance health‐promoting compounds accumulation in green and red lettuce

“…Control plants were placed for the same time in the climatic chamber where UV‐B lamps were screened by benzophenone‐treated polyethylene film. This kind of compound is known to block UV‐B radiation (Calvenzani et al, ). Ten plants were used in each treatment, in which after the first week a group of five plants was sampled (week 1) while the remaining plants were sampled at the end of the second week (week 2).…”

Biochemical and histological characterization of tomato mutants

“…The plethora of mutants available in tomato is the most advantageous characteristic of this model plant, through which the genetic and biochemical network of many responses is getting better understood (Emmanuel and Levy 2002, Thompson et al 2004, Calvenzani et al 2010. Additionally, an advantageous tool is the tomato mutant collection introgressed into the Micro-Tom (MT) (Carvalho et al 2011a), available at "HCPD-Lab Micro-Tom Mutants", a small size and rapid life cycle tomato cultivar (Meissner et al 1997), which has been and will be a successful material for exploitation of several aspects of plant development, such as hormonal and photomorphogenic responses (Gratão et al 2009, Carvalho et al 2010, Campos et al 2009).…”

Stress-induced flavonoid biosynthesis and the antioxidant machinery of plants

“…9 Our findings are consistent with the expression of genes of the biosynthesis of antioxidant flavonols (e.g., quercetin 3-O-glycosides), i.e., FLS (flavonol synthase) and F3'H (flavonoid 3'-hydroxylase) being strongly induced by a plethora of abiotic stresses, [10][11][12] including UV-B radiation. 13 Since different stresses have been reported to generate ROS, it has been speculated that stress-induced changes in ROS/REDOX homeostasis activate the biosynthesis of antioxidant flavonols, 3,14,15 this idea conforming to R2R3MYB transcriptor factors, which regulate the biosynthesis of flavonols, being themselves REDOX-controlled. 16 There is a large consensus for flavonoids to function as ROS scavengers, as they may inhibit the generation and reducing ROS once formed, 17 but the actual more stresses.…”