Isochorismate synthase transgenic expression in Catharanthus roseus cell suspensions

Cell suspensions of Catharanthus roseus produce 2,3-dihydroxybenzoic acid ( 2,3-DHBA) after elicitation with fungal elicitor. Together with the 2,3-DHB A production there is a strong increase in isochorismate synthase (IM EC 5. 4.99.6) activity, an enzyme which converts chorismate into isochorismate. B acteria also produce 2,3-DHBA which is an intermediate for the biosynthesis of siderophores. The biosynthesis pathway of 2,3-DHBA in bacteria proceeds via ICS. To investigate whether C. roseus cells use the same pathway to pr oduce 2,3-DHBA, cells were transformed with constructs containing a C. rose us cDNA clone of ics in sense or antisense orientation. Although the transf ormation with ics in sense orientation resulted in constitutive ICS activit y, no accumulation of 2,3-DHBA was observed. Transformation of ics in antis ense orientation was not sufficient to block the ICS production. The biosyn thesis of 2,3-DHBA in C. roseus probably involves a multi-enzyme pathway, w hich cannot simply be modulated by over-expression of ics. (C) 2001 Edition s scientifiques et medicales Elsevier SAS.