Premium
Multifunctional oxidosqualene cyclases and cytochrome P450 involved in the biosynthesis of apple fruit triterpenic acids
Author(s) -
Andre Christelle M.,
Legay Sylvain,
Deleruelle Amélie,
Nieuwenhuizen Niels,
Punter Matthew,
Brendolise Cyril,
Cooney Janine M.,
Lateur Marc,
Hausman JeanFrançois,
Larondelle Yvan,
Laing William A.
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13996
Subject(s) - biosynthesis , chemistry , cytochrome p450 , biochemistry , ripening , enzyme , biology , food science
Summary Apple ( Malus × domestica ) accumulates bioactive ursane‐, oleanane‐, and lupane‐type triterpenes in its fruit cuticle, but their biosynthetic pathway is still poorly understood. We used a homology‐based approach to identify and functionally characterize two new oxidosqualene cyclases (Md OSC 4 and Md OSC 5) and one cytochrome P450 ( CYP 716A175). The gene expression patterns of these enzymes and of previously described oxidosqualene cyclases were further studied in 20 apple cultivars with contrasting triterpene profiles. Md OSC 4 encodes a multifunctional oxidosqualene cyclase producing an oleanane‐type triterpene, putatively identified as germanicol, as well as β‐amyrin and lupeol, in the proportion 82 : 14 : 4. Md OSC 5 cyclizes 2,3‐oxidosqualene into lupeol and β‐amyrin at a ratio of 95 : 5. CYP 716A175 catalyses the C‐28 oxidation of α‐amyrin, β‐amyrin, lupeol and germanicol, producing ursolic acid, oleanolic acid, betulinic acid, and putatively morolic acid. The gene expression of Md OSC 1 was linked to the concentrations of ursolic and oleanolic acid, whereas the expression of Md OSC 5 was correlated with the concentrations of betulinic acid and its caffeate derivatives. Two new multifuntional triterpene synthases as well as a multifunctional triterpene C‐28 oxidase were identified in Malus × domestica . This study also suggests that Md OSC 1 and Md OSC 5 are key genes in apple fruit triterpene biosynthesis.