A Bacterial Virulence Protein Suppresses Host Innate Immunity to Cause Plant
Disease
A Bacterial Virulence Protein Suppresses Host Innate Immunity to Cause Plant
DiseaseNomura, K., Debroy, S., Lee, Y.H., Pumplin, N., Jones, J., and He, S.Y. (2006).
Science 313, 220-223.
Presented by: Bob Berkey
Nomura, K., Debroy, S., Lee, Y.H., Pumplin, N., Jones, J., and He, S.Y. (2006). Science 313, 220-223.
Presented by: Bob Berkey
BackgroundBackground
Plants have evolved immune system to defend against microbial organisms that attempt to inject virulence proteins to suppress immunityMammalian pathogens can regulate cytoskeleton, membrane composition, vesicle trafficking, and host immunityNot much is known about molecular mechanisms of bacterial effector proteins in plantsBelieved effector proteins suppress the host immune responses
Plants have evolved immune system to defend against microbial organisms that attempt to inject virulence proteins to suppress immunityMammalian pathogens can regulate cytoskeleton, membrane composition, vesicle trafficking, and host immunityNot much is known about molecular mechanisms of bacterial effector proteins in plantsBelieved effector proteins suppress the host immune responses
Pseudomonas syringaePseudomonas syringae
Gram negative plant pathogenic bacteriumOver 40 pathovars of P. syringaethat can infect a variety of plant species including economically important ones like tomatoExamined strains all use Type III secretion system for pathogenesis
Associated hrp/hrc genesExchangeable effector locusConserved effector locus
Gram negative plant pathogenic bacteriumOver 40 pathovars of P. syringaethat can infect a variety of plant species including economically important ones like tomatoExamined strains all use Type III secretion system for pathogenesis
Associated hrp/hrc genesExchangeable effector locusConserved effector locus
Paper OverviewPaper Overview
Looking for the molecular targets of bacterial virulence proteins important in disease development, specifically PstDC3000HopM1, conserved P. syringae virulence protein, targets the immunity associated protein AtMIN7 in Arabidopsis
Mediates this through proteasome degradation
Results show strategy of pathogens that exploit proteasome to overrun immunity and cause disease symptoms
Looking for the molecular targets of bacterial virulence proteins important in disease development, specifically PstDC3000HopM1, conserved P. syringae virulence protein, targets the immunity associated protein AtMIN7 in Arabidopsis
Mediates this through proteasome degradation
Results show strategy of pathogens that exploit proteasome to overrun immunity and cause disease symptoms
Previous Work & InformationPrevious Work & Information
Partial deletion of conserved effector locus in ∆CEL mutant
reduction of bacterial population and elimination of disease symptoms (tomato and Arabidopsis)
Deletion is functionally redundant effector genes hopM1 and avrE
HopM1: 712 amino acid protein translocated into cell during infection by type III system
pORF43: plasmid expressing HopM1 and cognate chaperone ShcM
Partial deletion of conserved effector locus in ∆CEL mutant
reduction of bacterial population and elimination of disease symptoms (tomato and Arabidopsis)
Deletion is functionally redundant effector genes hopM1 and avrE
HopM1: 712 amino acid protein translocated into cell during infection by type III system
pORF43: plasmid expressing HopM1 and cognate chaperone ShcM
HopM1 Transgenic Expression Recovers Virulence of ∆CEL Mutant & Important Regions for Virulence
Function of HopM1
HopM1 Transgenic Expression Recovers Virulence of ∆CEL Mutant & Important Regions for Virulence
Function of HopM1
Figure 1
Figure S1
Pink arrows indicate the dominant negativeeffect of HopM11-200 and HopM11-300 on ΔCEL mutant. Blue arrows indicate the ability of full-length HopM1 or HopM1101-712 to completely or partially complement the ΔCEL mutant
The Dominant Negative Effect & Y2H Screens
The Dominant Negative Effect & Y2H Screens
Figure 2
Figure S2B
Destabilization of AtMIN Protein(s) Necessary for promotion of P. syringae
Pathogenesis by HopM1
Destabilization of AtMIN Protein(s) Necessary for promotion of P. syringae
Pathogenesis by HopM1
Figure 3
Figure S4B
BFA Can Supplement for HopM1 and Restore Virulence
BFA Can Supplement for HopM1 and Restore Virulence
ARF GEF proteins: key pats of vesicle trafficking systemBFA: well known inhibitor of vesicle trafficking
ARF GEF proteins: key pats of vesicle trafficking systemBFA: well known inhibitor of vesicle trafficking
Figure 3C
AtMIN7 Required for Cell Wall Associated Defense
AtMIN7 Required for Cell Wall Associated Defense
Callose deposition: cellular marker of cell wall defense
Callose deposition: cellular marker of cell wall defense
Figure 4
ConclusionsConclusionsHopM1 is necessary for the destabilization of AtMIN7, a host ARF GEF family protein active in host immune response, through the proteasomeRecent findings show a P. syringae effector protein AvrPtoB has intrinsic E3 ligase activity and that vesicle trafficking and extra cellular secretion are important in immune response
HopM1 does not show sequence homology to AvrPtoB or common motifs for components of ubiquitination/proteasome systemHopM1 probably functions as an adaptor protein that targets AtMIN7 to degradation pathway
HopM1 is necessary for the destabilization of AtMIN7, a host ARF GEF family protein active in host immune response, through the proteasomeRecent findings show a P. syringae effector protein AvrPtoB has intrinsic E3 ligase activity and that vesicle trafficking and extra cellular secretion are important in immune response
HopM1 does not show sequence homology to AvrPtoB or common motifs for components of ubiquitination/proteasome systemHopM1 probably functions as an adaptor protein that targets AtMIN7 to degradation pathway
P. Syringae ActionsP. Syringae ActionsEliminated component of vesicle trafficking pathway in order to suppress cell wall associated host defenseSalmonella enericaModulation of trafficking is a common goal of human and plant pathogens
Eliminated component of vesicle trafficking pathway in order to suppress cell wall associated host defenseSalmonella enericaModulation of trafficking is a common goal of human and plant pathogens
Figure S6
Possible Future DirectionsPossible Future Directions
GFP fluorescent tag studies of HopM1Only looked at Pst DC3000, do other P. syringae strains work in a similar manner in regards to AtMIN proteins particularly AtMIN7?Mechanisms of AtMIN7 targeting for degradation, and what protein(s) is HopM1 functioning as adaptor with?Similar function results seen in Arabidopsis from other bacterial pathogens?Other molecular targets of HopM1 since BFA treatment showed more complete virulence recovery than AtMIN7 KO?
GFP fluorescent tag studies of HopM1Only looked at Pst DC3000, do other P. syringae strains work in a similar manner in regards to AtMIN proteins particularly AtMIN7?Mechanisms of AtMIN7 targeting for degradation, and what protein(s) is HopM1 functioning as adaptor with?Similar function results seen in Arabidopsis from other bacterial pathogens?Other molecular targets of HopM1 since BFA treatment showed more complete virulence recovery than AtMIN7 KO?