Cloning and characterization of novel methylsalicylic acid synthase gene involved in the biosynthesis of isoasperlactone and asperlactone in Aspergillus westerdijkiae

Nafees Bacha (1, 2, 3) , Huy Phong Dao (1, 2, 3) , Ali Atoui (4) , Florence Mathieu (1, 2, 3) , John O'Callaghan (5) , Olivier Puel (6) , Thierry Liboz (1, 2, 3) , Alan D.W. Dobson (5) , Ahmed Lebrihi (1, 2, 3)

1 UT3 - Université Toulouse III - Paul Sabatier
2 Toulouse INP - Institut National Polytechnique (Toulouse)
3 ENSAT - École nationale supérieure agronomique de Toulouse
4 CNRS - Centre National de la Recherche Scientifique
5 UCC - University College Cork
6 UPT - Unité de recherche Pharmacologie-Toxicologie

Aspergillus westerdijkiae is the main producer of several biologically active polyketide metabolites including isoasperlactone and asperlactone. A 5298 bp polyketide synthase gene ‘‘aomsas” has been cloned in Aspergillus westerdijkiae by using gene walking approach and RACE-PCR. The predicted amino acid sequence of aomsas shows an identity of 40–56% with different methylsalicylic acid synthase genes found in Byssochlamys nivea, P. patulum, A. terreus and Streptomyces viridochromogenes. Based on the reverse transcription PCR and kinetic secondary metabolites production studies, aomsas expression was found to be associated with the biosynthesis of isoasperlactone and asperlactone. Moreover an aomsas knockout mutant ‘‘aoDmsas” of A. westerdijkiae, not only lost the capacity to produce isoasperlactone and asperlactone,but also 6-methylsalicylic acid. The genetically complemented mutant ao+msas restored the biosynthesis of all the missing metabolites. Chemical complementation through the addition of 6-methylsalicylic acid, aspyrone and diepoxide to growing culture of aoDmsas mutant revealed that these compounds play intermediate roles in the biosynthesis of asperlactone and isoasperlactone.

Mots clés: ASPERGILLUS WESTERDIJKIAE; POLYKETIDE SYNTHASE; ASPERLACTONE; ISOASPERLACTONE; 6-METHYLSALICYLIC ACID; Aspergillus westerdijkiae; Polyketide synthase; Asperlactone; Isoasperlactone; 6-Methylsalicylicacid

Domaines: Génie chimique; Microbiologie et Parasitologie; Toxicologie végétale et mycotoxicologie

Nafees Bacha, Huy Phong Dao, Ali Atoui, Florence Mathieu, John O'Callaghan, et al.. Cloning and characterization of novel methylsalicylic acid synthase gene involved in the biosynthesis of isoasperlactone and asperlactone in Aspergillus westerdijkiae. Fungal Genetics and Biology, 2009, vol. 46 (n° 10), pp. 742-749. ⟨10.1016/J.FGB.2009.07.002⟩. ⟨hal-02665226⟩