Characterization of three members of the Arabidopsis carotenoid cleavage dioxygenase family demonstrates the divergent roles of this multifunctional enzyme family

Abstract

SummaryArabidopsis thaliana has nine genes that constitute a family of putative carotenoid cleavage dioxygenases (CCDs). While five members of the family are believed to be involved in synthesis of the phytohormone abscisic acid, the functions of the other four enzymes are less clear. Recently two of the enzymes, CCD7/MAX3 and CCD8/MAX4, have been implicated in synthesis of a novel apocarotenoid hormone that controls lateral shoot growth. Here, we report on the molecular and genetic interactions between CCD1, CCD7/MAX3 and CCD8/ MAX4. CCD1 distinguishes itself from other reported CCDs as being the only member not targeted to the plastid. Unlike ccd7/max3 and ccd8/max4, both characterized as having highly branched phenotypes, ccd1 loss-of-function mutants are indistinguishable from wild-type plants. Thus, even though CCD1 has similar enzymatic activity to CCD7/MAX3, it does not have a role in synthesis of the lateral shoot growth inhibitor. Rather, it may have a role in synthesis of apocarotenoid flavor and aroma volatiles, especially in maturing seeds where loss of function leads to significantly higher carotenoid levels.

Analysis of theDECREASED APICAL DOMINANCEGenes of Petunia in the Control of Axillary Branching

“…There are some significant differences in the phenotypes of plants carrying max3 or dad3 mutations. Whereas the dad1-1dad3 double mutant is additive in several aspects of its phenotype, it has been reported that the max3max4 mutant is not additive in phenotype (Auldridge et al, 2006). This indicates that either DAD3 is not orthologous to MAX3 or that they act in different ways in different species.…”

Cloning and characterisation of a maize carotenoid cleavage dioxygenase (ZmCCD1) and its involvement in the biosynthesis of apocarotenoids with various roles in mutualistic and parasitic interactions

“…However, several studies have suggested that the CCD1 enzymes reside in the cytosol. Indeed, AtCCD1 is the only Arabidopsis carotenoid cleaving enzyme which is not localised in plastids but in the cytosol (Auldridge et al 2006a) and immunolocalisation indicated that the Crocus CCD1 protein is also localised in the cytoplasm (Bouvier et al 2003). Prediction algorithms (SignaIP 3.0) clearly suggest that all CCD1 enzymes are devoid of a plastid targeting signal.…”

“…Among them, Wve are Vp14-like (NCED2,NCED3,NCED5,NCED6 and NCED9) and are supposed to be involved in ABA biosynthesis (Tan et al 2003). The other four have been given the generic designation carotenoid cleavage dioxygenase (CCD1, CCD4, CCD7 and CCD8) (Auldridge et al 2006a). Arabidopsis CCD1 (AtCCD1) symmetrically cleaves multiple trans-carotenoid substrates ( -carotene, lutein, zeaxanthin, trans-violaxanthin) at the 9, 10 and 9Ј, 10Ј double bonds producing a C 14 dialdehyde and two C 13 products that vary depending on the carotenoid substrate (Schwartz et al 2001).…”

Strigolactones as mediators of plant growth responses to environmental conditions

“…3,7,[26][27][28][29], and were suggested to sequentially catalyze carotenoid cleavage reactions. 30,31 Also, a cytochrome P450 monooxygenase, MAX1, was suggested to be involved in a later biosynthetic step, 2,32 whereas additional steps in SL synthesis are anticipated yet unknown. 1 As for the SLs signaling components, although the SLs receptor was not identified yet, MAX2, an F-box protein, was suggested to be a component of SL signaling and function in a ubiquitinemediated degradation of yet unknown protein targets.…”