Sequiterpene cyclase STCS: the missing link in the biosynthesis of abscisic acid
2016
Izquierdo-Bueno, Inmaculada | Dos Santos, Gabriel Franco | Gonzalez-Rodriguez, Victoria E. | Dalmais, Berengere | Pradier, Jean-Marc | Le Pecheur, Pascal | Moraga, Javier | Sanchez, Rosario | Carbu, Maria | Cantoral, Jesus M | Viaud, Muriel | Collado, Isidro G.
Advances in genomic studies, in combination with increased access to DNA sequencing, are providing a wealth of information about how natural products are assembled, mechanisms by which natural product gene clusters can be manipulated to yield new product diversity, and the genetic potential of individual organisms. Botrytis cinerea is a well-known pathogen of a number of commercial crops and produces many structurally diverse metabolites. Botrytis produces three series of sesquiterpenes, botrydial and its derivatives, a new family of eremophilenols and the phytohormone abscisic acid (ABA). Studies on ABA biosynthesis have identified a gene cluster of at least four genes responsible for this pathway in B. cinerea: two P450 monooxygenase-encoding genes (bcaba1 and bcaba2), an open reading frame (bcaba3), and a gene probably coding for a short-chain dehydrogenase/reductase (bcaba4). Until now, the sesquiterpene cyclase (STC) involved in the ABA biosynthesis has not yet been identified and it should be located in another part of the genome of B. cinerea. The metabolomic study of the strains ATCC G3, an overproducer of ABA, and null mutants ΔBcSTC5 and Δbcaba1-4, together with studies on the level of expression of the STC-encoding genes, have shown the STC5 as the sesquiterpene synthase involved in the ABA biosynthesis. Additionally, the studies of the transformants Δbcaba1-4 have allowed to present an updated ABA biosynthetic pathway.
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