Zeaxanthin at the 7,8(7 ,eight ) forming 3-hydroxy–cyclocitral and crocetin dialdehyde, the precursor for the formation of crocin plus the spice saffron (Figure eight; see Section 3.6.2) [139,245]. Ahrazem et al. [245] demonstrated that CsCCD2 needs a 3-hydroxy–ring and will not Plants 2021, ten, x FOR PEER Critique 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] along with the roots of Coleus forskohlii [247].Figure 8. Scheme for the 7,8(7 ,eight reactions catalysed by the recombinant carotenoid cleavage deFigure eight. Scheme for the 7,8(7,8,),) 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 5,six(five ,six ) thin, violaxanthin, antheraxanthin, lutein, zeaxanthin and -carotene in planta at five,6(5,six) and 9,ten(9,ten) positions, creating MHO (6-methyl-5-hepten-2-one) and also the 13 apocand 9,ten(9 ,10 ) positions, producing MHO (6-methyl-5-hepten-2-one) along with the CC13 apocarotenoids, 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], further demonstrating that CCD-generated apocarotenoids tolerance to limitation limitation [248], further demonstrating that CCD-generated apohave essential regulatory functions in planta. Finally, WangFinally, Wang et reported have carotenoids have essential regulatory functions in planta. et al. [201] have al. [201] that CCD10 is that CCD10 is located inplants only. As C13 apocarotenoids promote arbuscular reported identified in Moveltipril Autophagy mycorrhizal mycorrhizal plants only. As C13 apocarotenoids market mycorrhizalmycorrhizal symbiosis three.6.2 [228,249,250]); [228,249,250]); over-expression of arbuscular symbiosis (See Section (See Section 3.6.two over-expression of CCD10 beneath low phosphate low phosphate increaseswhich may well promote phosphate acquisition via the CCD10 under increases C13 formation, C13 formation, which may possibly promote phosphate acmycorrhiza fungal pathway (see [248]). quisition via the mycorrhiza fungal pathway (see [248]).3.five. Apocarotenoids Are Important to Flavour and Aroma 3.5. Apocarotenoids Are Significant to Flavour and Aroma Terpenoid flavour SBP-3264 web volatiles are usually present in plants at reasonably low low levels, Terpenoid flavour volatiles are commonly present in plants at fairly levels, but possess sturdy strong 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 considered to become among by far the most substantial contributors for the flavour [192,230,25156]. These CDCs are considere.
