The type III effectors HsvG and HsvB of gall-forming Pantoea agglomerans determine host specificity and function as transcriptional activators.
Pantoea agglomerans pv. gypsophilae (Pag) elicits galls on gypsophila and a hypersensitive response on beet, whereas P. agglomerans pv. betae (Pab) induces galls on both beet and gypsophila. The pathogenicity of both pathovars is dependent on the presence of a plasmid harbouring type III secretion system (TTSS) components and effectors. The HsvG TTSS effectors of Pag (HsvG-Pag) and Pab (HsvG-Pab) determine the host specificity of both pathovars on gypsophila. Here we describe a novel HsvG homologue, HsvB, which determines the host specificity of Pag and Pab on beet. HsvG requires two direct amino acid repeats for pathogenicity on gypsophila, whereas one repeat in HsvB is sufficient for pathogenicity on beet. Exchanging repeats between HsvG-Pag and HsvB-Pab resulted in a switch of host specificities. Transient expression of GFP-HsvG or GFP-HsvB fusions in gypsophila, beet or melon leaves showed that HsvG and HsvB were localized to the nuclei of host and non-host plants. A yeast one-hybrid assay revealed that a single repeat of HsvG or HsvB was sufficient to activate transcription. By employing random binding-site selection and gel-shift assay HsvG was demonstrated to be a double-stranded DNA-binding protein with an ACACC/aAA consensus binding site. These results suggest that HsvG and HsvB are host-specificity determinants and bear the potential to affect the host transcriptional machinery.
Nissan
Gal
G
Department of Plant Sciences, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel.
Manulis-Sasson
Shulamit
S
Weinthal
Dan
D
Mor
Henia
H
Sessa
Guido
G
Barash
Isaac
I
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D027461:Beta vulgaris / Q000382:microbiology; D029748:Caryophyllaceae / Q000382:microbiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D024202:Electrophoretic Mobility Shift Assay; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D020636:Pantoea / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D010957:Plasmids / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D013045:Species Specificity; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics; D020798:Two-Hybrid System Techniques; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C113709:HsvG protein, Pantoea agglomerans; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D049452:Green Fluorescent Proteins