['To investigate the effects of the organic solvent dimethyl sulfoxide (DMSO) on the expression of a citrate-inducible gene, encoding a putative tricarboxylate transporter, in Agrobacterium tumefaciens.', 'By two-dimensional gel electrophoresis, we discovered a putative tricarboxylate transporter named ActC, whose expression was downregulated by DMSO. The expression of actC is also induced by tricarboxylates but not affected by other organic acids of the TCA cycle. Intriguingly, transcriptional activation of actC by citrate is compromised in the presence of DMSO. Furthermore, expression of actC is abolished by deletion of actDE, encoding a putative two-component regulatory system upstream of the actCBA gene cluster.'] Is a citrate-inducible gene , encoding a putative tricarboxylate transporter , downregulated by the organic solvent DMSO in Agrobacterium tumefaciens?