Apocarotenoids plants

Walter, M.H., Fester, T., and Strack, D., Arbuscular mycorrhizal fungi induce the non-mevalonate methylerythritol phosphate pathway of isoprenoid biosynthesis correlated with accumulation of the yellow pigment and other apocarotenoids. Plant J. 21, 571, 2000. 

Plant apocarotenoids have a wide variety of structures and functions. As expected, there is a small gene family of CCDs with different cleavage sites and somewhat promiscuous substrate selection. Some CCDs are stereo-specific, for example, 9-cis epoxycarotenoids are the substrates for NCEDs (9-cis expoxy dioxygenases) that produce the precursor of ABA biosynthesis, xanthoxin. Both linear carotenoids (lycopene) and cyclic carotenoids are substrates for cleavage at various double bonds including the central 15-15 and eccentric 5-6, 7-8, 9-10, 9 -10, and 11-12 bonds. Some CCDs cleave both linear and cyclic carotenoids and may cleave the same molecule twice, e.g., both 9-10 and 9 -10 positions. 

Little is known of how the biosynthetic metabolon is assembled, what mechanisms control the membrane-specific targeting, and how the conversions to apocarotenoids occur. Yet the current approach to drive import of bacterial or plant genes is to use transit sequences of a stromal protein that may limit the effectiveness of the transgene. In addition, for specific applications of controlling carotenoid composition, we need to better understand the interactions of the various enzymes,... 

Castillo, R., Fernandez, J.A., and Gomez-Gomez, L., Implications of carotenoid biosynthetic genes in apocarotenoid formation during the stigma development of Crocus sativus and its closer relatives, Plant Physiol. 139, 674, 2005. 

Auldridge, M.E., McCarty, D.R., and Klee, H.J., Plant carotenoid cleavage oxygenases and their apocarotenoid products, Curr. Opin. Plant Biol. 9, 315, 2006. 

Apocarotenoids also act as chemoattractants, repellants, and growth effectors in plants and cyanobacteria. They attract pollinators to plants through the use of color similar to full-length carotenoids. Their aromas are thought to be attractants for animals and insects to facilitate in seed dispersal and pollination. Small volatile apocarotenoids lure pollinators and levels of apocarotenoids... 

Fester, T., B. Hause et al. (2002). Occurrence and localization of apocarotenoids in arbuscular mycorrhizal plant roots. Plant Cell Physiol. 43(3) 256-265. 

Carotenoid catabolic products also have a physiological role in the plant. Oxidative cleavage of carotenoids by carotenoid cleavage dioxygenases (CCDs) generates apocarotenoids [21]. Apocarotenoids serve the plant as antifungal agents or in the synthesis of flavor or aroma of flowers and fruits. A well-known downstream product of an apocarotenoid is abscisic acid (ABA), a phytohormone in plants [21]. 

Colonization of barley, wheat and maize and rice roots by Glomus intraradices resulted in strong induction of transcript levels of the pivotal enzymes of methylerythritol phosphate pathway of isoprenoid biosynthes i.e., 1 -deoxy-D-xylulose 5-phosphate synthase (DXS) and 1 -deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) (Walter et al., 2000). At the same time six cyclohexenone derivatives were characterized from mycorrhizal wheat and maize roots. DXS2 transcript levels are low in most tissues but are strongly stimulated in roots upon colonization by mycorrhizal fungi, correlated with accumulation of carotenoids and apocarotenoids (Walter et al., 2002). Some reports show that the AM symbiosis may cause an increase, decrease, or no change in the plant defense reactions (Guenoune et al., 2001 Mohr et al., 1998). 

Walter M.H., Hans J., StrackD. Two distantly related genes encoding 1-deoxy-D-xylulose 5-phosphate synthases differential regulation in shoots and apocarotenoid-accumulating mycorrhizal roots. Plant J 2002 31 243-254. 

Many compounds with fewer than 40 carbon atoms, but with carotenoid-like structures, are found in nature. Synthesis of these compounds, sometimes called apocarotenoids, appears to occur mainly by catabolism of carotenoids (Parry and Horgan, 1991). Apocarotenoids in the range of C9-C13 are found in plant essential oils, but others, ranging up to C30 compounds, are essentially nonvolatile. However, knowledge of the biochemistry of carotenoid metabolism is limited (Parry and Horgan, 1991). In vitro, photooxidation of carot-... 

Unlike the terpenoid families discussed so far, tetraterpenoids consist of only one class, namely carotenoids, the yellow and red pigments of plants. At present, about 500 different carotenoids are known. A vast majority of these are C40 compounds, though compounds with fewer than 40 (nor- and apocarotenoids - e.g., C30) and more than 40 (homocarotenoids - e.g. C50) carbon atoms have been isolated. The occurrence, chemistry, and biochemistry of carotenoids have been covered in a number of reviews and books (67, 124, 163, 216, 254, 282, 365). 

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