Versatile regulation of effectors by novel orthologous regulators in the <i>Legionella</i> genus

<i>Legionella pneumophila</i> translocates into host cells the largest number of effector proteins known in any pathogen. This cohort of proteins needs to be coordinated at the gene expression level to result in a successful infection. To date, the regulation of effector-encoding genes in <i>L. pneumophila</i> has been found to be mediated by global regulators that control the expression of multiple effectors and local regulators that control the expression of a single or few effectors. Here, we identified two novel regulators that function as local regulators of effectors in <i>L. pneumophila</i>. However, analysis of their orthologs across the <i>Legionella</i> genus revealed that one of them controls the expression of multiple genes in five <i>Legionella</i> species. The properties of the proteins encoded by these genes suggest that most of them function as effectors. Our data demonstrate a versatile regulator whose orthologs function as local or global regulators of EEGs in different <i>Legionella</i> species.