Te of CCD4 in planta (Bruno et al., 2015). Nonetheless, other members
Te of CCD4 in planta (Bruno et al., 2015). Even so, other members in the CCD4 subfamily show distinctive regional and substrate specificity. For example, Citrus CCD4 enzymes cleave the C7′ 8′ double bond in -carotene, ,-cryptoxanthin, and zeaxanthin, major for the fruit peel pigments, -apo-8′-carotenal and -citraurin, along with the volatiles, cyclocitral and 3-OH-cyclocitral (Rodrigo et al., 2013; Ma et al., 2013). CCD enzymes may well also kind hitherto unknown regulatory compounds. Aside from ABA and SLs, further carotenoid-derived regulatory molecules have already been postulated and believed to arise by means of cleavage of desaturation intermediates on the carotenoid biosynthesis pathway (Fig. 1) (Moise et al., 2014). For example, the tomato SCF Protein Formulation tangerine mutant is impaired in the activity of carotenoid cis-trans isomerase (CRTISO; Fig. 1), which final results in 7,9,7′,9′-tetra-cis-lycopene (prolycopene) accumulation in fruits, though the r(2997) yellow-flesh does not express the fruit-specific phytoene synthase gene (PSY1), top to a lack of fruit carotenoids. It was shown that the accumulation of prolycopene and its polycis-configured precursors in the yellow-flesh background is accompanied by a partial restoration of PSY1 transcription. This epistatic behavior in the downstream over the upstream pathway activity is thought to become mediated by carotene cleavage item(s) derived from prolycopene or its much less desaturated precursors (Kachanovsky et al., 2012). Furthermore, theFig. 1. Carotenoid biosynthesis and formation of carotenoid-derived signaling molecules. Desaturation intermediates are IL-3 Protein medchemexpress shaded. The scheme shows established and hypothetical signals generated by carotenoid cleavage dioxygenases (CCDs). The formation of abscisic acid and SLs is initiated by 9-cis-epoxycarotenoid cleavage dioxygenases (NCEDs) and CCD7, respectively. Hypothetical signals are indicated by a query mark. PSY, phytoene synthase; PDS, phytoene desaturase; Z-ISO, -carotene isomerase; CRTISO, carotenoid cis-trans isomerase; LCY-b, lycopene -cyclase; D27 (DWARF27), all-trans/9-cis–carotene isomerase. See text for additional explanations.as the phytohormones abscisic acid (ABA) (Schwartz et al., 1997; Zhu, 2002; Search engine marketing, 2002) and the strigolactones (SLs; Alder et al., 2012; Al-Babili and Bouwmeester, 2015). The Arabidopsis CCD family includes nine enzymes classified as either 9-cis-epoxycarotenoid dioxygenases (NCEDs), NCED2, 3, 5, six, and 9, or CCDs, CCD1, 4, 7, and 8. NCEDs are involved in ABA biosynthesis and catalyze the stereospecific cleavage from the C11 12 double bond in 9-cis-configured epoxycarotenoids, to yield the ABA precursor xanthoxin (Schwartz et al., 1997). CCD1 may be the only plant CCD which is localized inside the cytosol. Arabidopsis AtCCD1 (Schwartz et al., 2001) and homologs from a number of plant species catalyze symmetrical double cleavage in the C9 ten and C9’C10′ double bonds in cyclic and acyclic all-trans-configured carotenoids. CCD1 enzymes also target other double bonds in linear carotenes, yielding flavors, like 6-methyl-5-hepten2-one, geranial, and farnesyl acetone (Vogel et al., 2008; Ilg et al., 2009, 2014). Extra cleavage sites in apocarotenoids have also been documented (Ilg et al., 2014). In addition, it was assumed that CCD1-type enzymes convert apocarotenoids in lieu of carotenoids in planta and that they might act as a scavenger for oxidatively broken carotenoids (ScherzingerAtCCD7 and AtCCD4 in plastid retrograde signaling |use of Arabidopsis mutants.