Zeaxanthin in the 7,eight(7 ,eight ) forming 3-hydroxy–cyclocitral and crocetin dialdehyde, the precursor for the formation of crocin along with the spice saffron (YTX-465 Technical Information Figure 8; see Section 3.6.two) [139,245]. Ahrazem et al. [245] demonstrated that CsCCD2 calls for a 3-hydroxy–ring and will not Plants 2021, 10, x FOR PEER Review 20 of 40 use –carotene or lycopene as a substrate. Crocetin dialdehyde has previously been shown to accumulate within the flowers of Jacquinia angustifolia [246] plus the roots of Coleus forskohlii [247].Figure eight. Scheme for the 7,eight(7 ,8 reactions catalysed by the recombinant carotenoid cleavage deFigure 8. Scheme for the 7,8(7,eight,),) reactions catalysed by the recombinant carotenoid cleavage oxygenases two two Crocus sativus. deoxygenases inin Crocus sativus.A second novel carotenoid cleavage enzyme, the Zea maize CCD10a, cleaved neoxanA second novel carotenoid cleavage enzyme, the Zea maize CCD10a, cleaved neoxanthin,violaxanthin, antheraxanthin, lutein, zeaxanthin and -carotene in planta at five,six(5 ,6 ) thin, violaxanthin, antheraxanthin, lutein, zeaxanthin and -carotene in planta at 5,six(5,6) and 9,10(9,ten) positions, producing MHO (6-methyl-5-hepten-2-one) as well as the 13 apocand 9,ten(9 ,10 ) positions, generating MHO (6-methyl-5-hepten-2-one) along with the CC13 apocarotenoids, WZ8040 manufacturer geranylacetone, -ionone and -ionone [248]. ZmCCD10 over-expression arotenoids, geranylacetone, -ionone and -ionone [248]. ZmCCD10 over-expression and and down-regulation led to alterations in expression of phosphate starvation response down-regulation led to alterations in thethe expression of phosphate starvationresponse regulators (PHR1) and phosphate transporters, whereas down-regulation of CCD10a regulators (PHR1) and phosphate transporters, whereas down-regulation of CCD10a produced produced plants susceptible to Pi deficiency, over-expression in Arabidopsis plant tolerance plants susceptible to Pi deficiency, over-expression in Arabidopsis enhanced enhanced plant to phosphatephosphate [248], additional demonstrating that CCD-generated apocarotenoids tolerance to limitation limitation [248], additional demonstrating that CCD-generated apohave crucial regulatory functions in planta. Ultimately, WangFinally, Wang et reported have carotenoids have vital regulatory functions in planta. et al. [201] have al. [201] that CCD10 is the fact that CCD10 is identified inplants only. As C13 apocarotenoids promote arbuscular reported found in mycorrhizal mycorrhizal plants only. As C13 apocarotenoids market mycorrhizalmycorrhizal symbiosis 3.6.two [228,249,250]); [228,249,250]); over-expression of arbuscular symbiosis (See Section (See Section 3.six.2 over-expression of CCD10 below low phosphate low phosphate increaseswhich may perhaps market phosphate acquisition through the CCD10 below increases C13 formation, C13 formation, which may well market phosphate acmycorrhiza fungal pathway (see [248]). quisition via the mycorrhiza fungal pathway (see [248]).three.5. Apocarotenoids Are Essential to Flavour and Aroma 3.5. Apocarotenoids Are Crucial to Flavour and Aroma Terpenoid flavour volatiles are commonly present in plants at relatively low low levels, Terpenoid flavour volatiles are generally present in plants at fairly levels, but possess powerful powerful around the overallthe overall human on the flavour of [192,230,25156]. but possess effects effects on human appreciation appreciation of the flavour of these CDCs are regarded as to be amongst by far the most important contributors for the flavour [192,230,25156]. These CDCs are considere.
