Malic enzyme encoded by the gene scfA belongs to the core set of housekeeping genes encoded by phytoplasmas. It enables the conversion of malate to pyruvate, an essential step in the unique pathway of phytoplasmas resulting in the generation of ATP and acetate. Several studies have examined the functionality of this pathway and the phylogenetic origin back to its putative Gram-positive source. The current sequence information on the enzyme relies on available genome sequence data. Comparison of scfA gene sequences highlights a low number of conserved sites, even between closely related strains, thereby hampering the design of universal primer pairs for application in PCR. A primer set was designed that enables the amplification of this key gene in phytoplasma metabolism. Successful amplification was performed from strains covering the three main phylogenetic branches of phytoplasma, and, as such, the universal primers scfA115F/865R offer the ability to obtain additional data from closely and distantly related phytoplasmas.
R. Toth, E. Seemüller, M. Kube