Carotenoids encoding genes

Although carotenogenesis in plants takes place in plastids, all of the carotenoid biosynthesis genes are nuclear encoded and their polypeptide products are imported into the plastids. Therefore, they contain a N-terminal transit peptide sequence. For example, the size of the transit peptide of PSY from ripe tomato fruit is approximately 9 kDa, corresponding to about 80 amino acid residues (Misawa et al, 1994). 

In tomato two PSY encoding genes have been identified Psy-1 and Psy-2. Psy-1 encodes the fruit-ripening-specific isoform, which has been proved to be the key enzyme in the control of carotenoid biosynthesis [28]. Psy-2 encoded enzyme predominates in green tissues (including mature green fruit) and petals and has no role in carotenoid synthesis in ripening fruit [29, 26]. As an example of the role of this enzyme in carotenoid biosynthesis, a null mutation in Psy-1 in the yellow-flesh (r) mutant arrests carotenoid synthesis [30]. In this mutant, the accumulation of the flavonoid rutin in the fruit skin would lead to the development of yellowish fruits. 

Nishida Y, Adachi K, Kasai H, Shizuri Y, Shindo K, Sawabe A, Komemushi S, Miki W, Misawa N (2005) Elucidation of a carotenoid biosynthesis gene cluster encoding a novel enzyme, 2,2 -P-hydroxylase, from Brevundimonas sp. strain SD212 and combinatorial biosynthesis of new or rare xanthophylls. Appl Environ Microbiol 71 4286-4296... 

Bartley, G.E. et ah, A tomato gene expressed during fruit ripening encodes an enzyme of the carotenoid biosynthesis pathway, J. Biol. Chem. 267, 5036, 1992. 

Romer, S. et al.. Expression of the genes encoding the early carotenoid biosynthetic enzymes in Capsicum annuum, Biochem. Biophys. Res. Commun. 196, 1414, 1993. 

Chen, H.C., Klein, A., Xiang, M.H., Backhaus, R.A. and Kuntz, M. (1998) Drought and wound induced expression in leaves of a gene encoding a chromoplast carotenoid associated protein. Plant Journal 14(3), 317-326. 

The Heliobacteriaceae only have Cj acyclic carotenes, 4,4"-diapocarotenes, instead of the usual carotenoids (Fig. 11 Takaichi et al., 1997b). 4,4"-Diaponeurosporene is the major carotene, and diapophytoene, diapophytofluene, diapo-C-carotene and diapolycopene are also found as minor components. Two genes encoding enzymes in the early steps of diapocarotene biosynthesis have been... 

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