Expression of Xanthophyll Biosynthetic Genes during Light-Dependent Chloroplast Differentiation

Abstract

In higher plants, etioplast to chloroplast differentiation is characterized by dramatic ultrastructural changes of the plastid and a concomitant increase in chlorophylls and carotenoids. Whereas the formation and function of carotenes and their oxygenated derivatives, the xanthophylls, have been well studied, little is known about the regulation of the genes involved in xanthophyll biosynthesis. Here, we analyze the expression of three xanthophyll biosynthetic genes (i.e. ␤-carotene hydroxylase [bhy], zeaxanthin epoxidase [zep], and violaxanthin de-epoxidase [vde]) during de-etiolation of seedlings of tobacco (Nicotiana tabacum L. cv Samsun) under different light conditions. White-light illumination caused an increase in the amount of all corresponding mRNAs. The expression profiles of bhy and zep not only resembled each other but were also similar to the pattern of a gene encoding a major light-harvesting protein of photosystem II. This finding indicates a coordinated synthesis during formation of the antenna complex. In contrast, the expression pattern of vde was clearly different. Furthermore, the gene expression of bhy was shown to be modulated after illumination with different white-light intensities. The expression of all xanthophyll biosynthetic genes under examination was up-regulated upon exposure to red, blue, and white light. Gene expression of bhy and vde but not of zep was more pronounced under red-light illumination, pointing at an involvement of the phytochrome system. Expression analysis in the presence of the photosynthetic electron transport inhibitors 3-(3,4-dichlorophenyl)-1,1-dimethyl-urea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone indicated a redox control of transcription of two of the xanthophyll biosynthetic genes (bhy and zep).

PSY3, a New Member of the Phytoene Synthase Gene Family Conserved in the Poaceae and Regulator of Abiotic Stress-Induced Root Carotenogenesis

“…However, the response mechanism may not involve increased flux to ABA because leaf ABA biosynthesis is limited not by the carotenoid precursor pool, but by NCED-mediated conversion of the xanthophyll precursors to ABA (Parry et al, 1990;Marin et al, 1996;Audran et al, 1998;Thompson et al, 2000a). Instead, increased carotenoid flux in leaves may relate to other processes, such as photosynthesis, temperature stress tolerance, and photoprotection (Davison, 2002;Rossel et al, 2002;Woitsch and Romer, 2003;Havaux et al, 2007). Nonstressed embryo, dissected at 20 d after pollination (DAP), contains few accumulated carotenoids, and the most prevalent PSY transcripts were those of PSY2 followed by PSY3; perhaps, in this tissue, which is lacking in photosynthetic plastids, PSY expression could possibly relate to plant development (Sorefan et al, 2003;Booker et al, 2004) and/or apocarotenoid biosynthesis (Matusova et al, 2005).…”

Daucus carota as a novel model to evaluate the effect of light on carotenogenic gene expression

“…Carotenoids are synthesized during light exposure, but it was shown that when light intensity increases from 150 to 280 mmol m -2 s -1 the rate of photo oxidation is higher than the rate of synthesis and carotenoids are destroyed, reaching a basal level (Simkin et al, 2003). The level of expression of some carotenogenic genes are reduced following prolonged illumination at moderate light intensities (Woitsch and Römer, 2003), as was shown for pds transcript accumulation in tomato seedlings and was referred to as inhibition by final product (lycopene) (Corona et al, 1996;Giuliano et al, 1993). This phenomenon could also explain the behavior of carrot zds1.…”

“…Almost all of these studies show that carotenogenic genes are expressed in photosynthetic organs exposed to different light qualities, during the transition of etioplasts to chloroplasts (de-etiolation) (Römer and Fraser, 2005;Bramley, 2002). During these processes, carotenogenic gene expression is mostly regulated at the transcriptional level mediated by photoreceptors, such as the family of phytochromes (PHYA-PHYE), cryptochromes (CRY) and phototropins (Simkin et al, 2003;Woitsch and Römer, 2003;Briggs and Olney, 2001;Scheppens et al, 2004, Franklin et al, 2005Briggs et al, 2007).…”

An Orange Ripening Mutant Links Plastid NAD(P)H Dehydrogenase Complex Activity to Central and Specialized Metabolism during Tomato Fruit Maturation

“…While most structural genes of the pathway have been characterized (Hirschberg, 2001), very little is known regarding the regulatory network that controls carotenogenesis. The control of carotenoid biosynthesis via the redox status of components of the photosynthetic electron transport has been established during etioplast-tochloroplast transition (Woitsch and Romer, 2003). In earlier studies, the involvement of quinones in carotenoid desaturation was demonstrated biochemically (Mayer et al, 1990) and genetically (Norris et al, 1995).…”