Identification, characterization and comparative analysis of a novel chorismate mutase gene in Arabidopsis thaliana

Phenylalanine, tyrosine, and tryptophan have a dual biosynthetic role in pl ants; they are required for protein synthesis and are also precursors to a number of aromatic secondary metabolites critical to normal development and stress responses. Whereas much has been learned in recent years about the genetic control of tryptophan biosynthesis in Arabidopsis and other plants, relatively little is known about the genetic regulation of phenylalanine a nd tyrosine synthesis. We have isolated, characterized and determined the e xpression of Arabidopsis thaliana genes encoding chorismate mutase, the enz yme catalyzing the first committed step in phenylalanine and tyrosine synth esis. Three independent Arabidopsis chorismate mutase cDNAs were isolated b y functional complementation of a Saccharomyces cerevisiae mutation. Two of these cDNAs have been reported independently (Eberhard et al., 1993. FEES 334, 233-236; Eberhard et al., 1996. Plant J. 10, 815-821), but the third ( designated CM-3) represents a novel gene. The different organ-specific expr ession patterns of these cDNAs, their regulation in response to pathogen in filtration, as well as the different enzymatic characteristics of the prote ins they encode are also described. Together, these data suggest that each isoform may play a distinct physiological role in coordinating chorismate m utase activity with developmental and environmental signals. (C) 1999 Elsev ier Science B.V. All rights reserved.