Carotenoid gene expression explains the difference of carotenoid accumulation in carrot root tissues

Abstract

Main conclusion Variations in gene expression can partially explain the difference of carotenoid accumulation in secondary phloem and xylem of fleshy carrot roots. The carrot root is well divided into two different tissues separated by vascular cambium: the secondary phloem and xylem. The equilibrium between these two tissues represents an important issue for carrot quality, but the knowledge about the respective carotenoid accumulation is sparse. The aim of this work was (i) to investigate if variation in carotenoid biosynthesis gene expression could explain differences in carotenoid content in phloem and xylem tissues and (ii) to investigate if this regulation is differentially modulated in the respective tissues by water-restricted growing conditions. In this work, five carrot genotypes contrasting by their root color were studied in control and water-restricted conditions. Carotenoid content and the relative expression of 13 genes along the carotenoid biosynthesis pathway were measured in the respective tissues. Results showed that in orange genotypes and the purple one, carotenoid content was higher in phloem compared to xylem. For the red one, no differences were observed. Moreover, in control condition, variations in gene expression explained the different carotenoid accumulations in both tissues, while in water-restricted condition, no clear association between gene expression pattern and variations in carotenoid content could be detected except in orange-rooted genotypes. This work shows that the structural aspect of carrot root is more important for carotenoid accumulation in relation with gene expression levels than the consequences of expression changes upon water restriction.

Carrot Genotypes Contrasted by Root Color and Grown under Different Conditions Displayed Differential Pharmacological Profiles in Vascular and Metabolic Cells

“…In present study, six genotypes contrasted by their root color have been considered. It is well established that orange carrot genotypes contain mostly α-carotene and β-carotene, yellow genotypes contain lutein, the red ones contain lycopene, and white genotypes contain almost no carotenoids [23]. Among carrots with the same color, total carotenoid content can vary greatly [6,24].…”

Unique chromoplast organisation and carotenoid gene expression in carotenoid-rich carrot callus

“…This corroborates differential PSY gene expression found in carrot root phloem tissue containing higher carotenoid contents than xylem. The expression of PSY2 in phloem was much higher relative to xylem, while PSY1 was stable or only slightly increased (Perrin et al 2017). However, high carotenoid accumulation in d-o callus can be only partially explained by PSY2 upregulation, as its transcript level was almost four-fold lower than in the root, containing similar amounts of carotenoids.…”

FACTORS AFFECTING CAROTENOID AMOUNT IN CARROTS (Daucus Carota)

“…In the work studied in control and water-restricted conditions with five carrot genotypes contrasting by their root color, carotenoid content and the relative expression of 13 genes along the carotenoid biosynthesis pathway were measured in the respective tissues. This work shows that the structural aspect of carrot root is more important for carotenoid accumulation in relation with gene expression levels than the consequences of expression changes upon water restriction [29].…”