Rhizobia utilize pathogen-like effector proteins during symbiosis.
A type III protein secretion system (T3SS) is an important host range determinant for the infection of legumes by Rhizobium sp. NGR234. Although a functional T3SS can have either beneficial or detrimental effects on nodule formation, only the rhizobial-specific positively acting effector proteins, NopL and NopP, have been characterized. NGR234 possesses three open reading frames potentially encoding homologues of effector proteins from pathogenic bacteria. NopJ, NopM and NopT are secreted by the T3SS of NGR234. All three can have negative effects on the interaction with legumes, but NopM and NopT also stimulate nodulation on certain plants. NopT belongs to a family of pathogenic effector proteases, typified by the avirulence protein, AvrPphB. The protease domain of NopT is required for its recognition and a subsequent strong inhibition in infection of Crotalaria juncea. In contrast, the negative effects of NopJ are relatively minor when compared with those induced by its Avr homologues. Thus NGR234 uses a mixture of rhizobial-specific and pathogen-derived effector proteins. Whereas some legumes recognize an effector as potentially pathogen-derived, leading to a block in the infection process, others perceive both the negative- and positive-acting effectors concomitantly. It is this equilibrium of effector action that leads to modulation of symbiotic development.
Kambara
Kumiko
K
Laboratoire de Biologie Moléculaire des Plantes Supérieures, Sciences III, 30 Quai Ernest-Ansermet, Université de Genève, CH-1211 Geneva 4, Switzerland.
Ardissone
Silvia
S
Kobayashi
Hajime
H
Saad
Maged M
MM
Schumpp
Olivier
O
Broughton
William J
WJ
Deakin
William J
WJ
D001426:Bacterial Proteins / Q000378:metabolism*; D007887:Fabaceae / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames; D012231:Rhizobium / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053204:Root Nodules, Plant / Q000382:microbiology*; D013045:Species Specificity; D013559:Symbiosis
D001426:Bacterial Proteins