Effects of exogenous glucose on carotenoid accumulation in tomato leaves

Abstract

To investigate the effect of carbohydrate on carotenoid accumulation in leaves, excised plants of tomato (Lycopersicum esculentum var. cerasiformae, wva 106) were supplied with glucose through the transpiration stream for 48 h. We report here that sugar accumulation in leaves led to a decrease of carotenoid content, which was related to the reduction of Chl. The decrease in carotenoid amount correlated with a sugar-induced repression of genes encoding enzymes of the carotenoid and of the Rohmer pathways. The lower 1-deoxy-D-xylulose-5-phosphate synthase transcript level probably leads to a decreased metabolic flux through the methylerythritol pathway and subsequently to a lower amount of substrate available for plastidic isoprenoid synthesis. Differences between responses of young (sink) and mature (source) leaves to carbohydrate accumulation are discussed.

Effect of fruit load on maturity and carotenoid content of clementine (Citrus clementina Hort. ex Tan.) fruits

“…The emerging mechanistic view of physiologists is rather one of a modulating role of carbohydrates regarding biogenesis of secondary metabolites 30, 35, 36. For instance, accumulation of soluble sugars in tomato leaves was observed to repress genes encoding enzymes of the carotenoid as well as the Rohmer pathway 37. It would certainly be useful to investigate the effect of carbohydrate accumulation on the major genes of the biosynthetic pathway of carotenoids in fruits in the future.…”

Carotenoid responses to environmental stimuli: integrating redox and carbon controls into a fruit model

“…This may explain why, in conditions of low Q (i.e. in conditions which are not conducive to photoinhibition), glucose supply can result in a decrease in carotenogenesis (Mortain-Bertrand et al 2008), and not an increase as one would predict from the ROS theory. It would also certainly be useful to identify which specific carotenoids accumulate and which ones decrease as a consequence of photoinhibition.…”

“…2). Accordingly, glucose accumulation in tomato leaves was observed to repress genes encoding enzymes of the carotenoid as well as of the MEP pathway (Mortain-Bertrand et al 2008). These apparently contradictory views about the effect of soluble sugars on the synthesis of carotenoids probably reflect the existence of two distinct strategies in leaves as a function of light exposure, the first one leading to a gain of carotenoids to enhance protection against photodamage, and the other leading to a loss of carotenoids when senescence is triggered.…”

Effect of prolonged root hypoxia on the antioxidant content of tomato fruit

“…Reverse transcription was carried out using 1 g of total RNA as described in Mortain-Bertrand et al [52]. Typical reactions were performed using 10 mM dNTPs, 0.6 M oligo-dT, 20 units of Rnasin (Promega), 2 mM DTT and 400 units of M-MLV reverse transcriptase (Promega).…”