Recent advances in

1
Recent advances in understanding gene for
gene interactions
2
Avirulence Gene Function what is currently
known
Avr Protein    
Pathogen    
Homology with and/or possible virulence function
    
Location in the plant cell
Common domain for avirulence and virulence
function    
Location of the matching R gene     





AvrPphC    
Pseudomonas syringae pv. phaseolicola    
Interferes with the plant defense response
NK     
NK    
NK    












AvrPphF    
Pseudomonas syringae pv. phaseolicola    
Interferes with the plant defense response
NK    
NK    
NK    












AvrRpt2    
Pseudomonas syringae pv. tomato    
Interferes with the plant defense response
NK    
NK    
NK    












AvrRpm1    
Pseudomonas syringae pv. maculicola    
Enhances growth
Plasma membrane
NK    
Plasma membrane












AvrPto    
Pseudomonas syringae pv. tomato    
Enhances growth Degradation of resistance gene
    
Plasma membrane
No
NK    












AvrBst    
Xanthomonas campestris pv. campestris    
Ubiquitin-like protease
NK    
Yes
NK    












AvrXa7    
Xanthomonas oryzae pv. oryzae    
Transcriptional activation domain required for
virulence
Nucleus
Yes
NK    












AvrBs2    
Xanthomonas campestris pv. vesicatoria    
Agrocinopine synthase (from Agrobacterium
tumefaciens)    
NK    
Recognition region localized in the portion with
highest homology to synthase
NK    












AvrBs3    
Xanthomonas campestris pv. glycinea    
Transcriptional activation domain required for
virulence  
Nucleus   
Yes  
NK    












PthA    
Xanthomonas citri    
Transcriptional activation domain required for
virulence/causes cell hyperplasia 53    
Nucleus    
NK    
NK    


















Avr9    
Cladosporium fulvum    
NK    
Exoplasmic    
NK    
External plasma membrane    
3
Avirulence genes promote virulence
Chen et al., (2000) The Pseudomonas syringae
avrRpt2 Gene Product Promotes Pathogen Virulence
from Inside Plant Cells. Molecular Plant-Microbe
Interactions Vol. 13 13121321
Disease symptoms and growth of Pseudomonas
syringae pv. tomato strain DC3000 (PstDC3000) on
Arabidopsis thaliana leaf tissue. A,
Diseasesymptoms caused by PstDC3000 on A.
thaliana No-0 rps2 (top) and Col-0 rps2 (bottom)
plants. Leaves are shown 4 days after inoculation
with PstDC3000 (left) and PstDC3000(avrRpt2)
(right). Plants were inoculated by dipping them
into bacterial suspensions (3 to 5 10 8 CFU/cm
2 ) containing the surfactant Silwet L-77. B,
Growth of PstDC3000 and PstDC3000(avrRpt2) in
leaf tissue of Col-0 rps2, No-0 rps2, and No-0
RPS2 plants.. In B, A. thaliana plants were
inoculated by vacuum infiltration with the
indicated PstDC3000 strains at an initial density
of 1 10 5 CFU/cm 2 . The concentration of
bacteria in the plant leaves was assayed after 0,
2, and 4 days. Datapoints represent means of
three independent determinations standard error
of the mean. Experiments presented in A, B, were
carried out a minimum of three times with similar
results
4
Virulence genes suppress avr/R gene interactions
Chen et al., (2000) The Pseudomonas syringae
avrRpt2 Gene Product Promotes Pathogen Virulence
from Inside Plant Cells. Molecular Plant-Microbe
Interactions Vol. 13 13121321
5
RPM1MYC is a peripheral PM protein.
C-Myc epitope has been artificially added to
RPM1
Anti-myc antibody can be used to detect
myc- labelled RPM1
Plasma Membrane
Cytoplasm and ER
Boyes et al., (1998) The Arabidopsis thaliana
RPM1 disease resistance gene product is a
peripheral plasma membrane protein that is
degraded coincident with the hypersensitive
response. 95, PNAS USA 15849-15854
6
AvrRpm1 and avrB localise to the plant cell
membrane. Protoplasts from rpm1 plants were
transformed with plasmid that express either
avr-GFP or avrG2A-GFP constructs. Control
transformations were with GFP alone.
avrRpm1 N-terminal fatty acylation sequence
avrRpm1 MGCVSSTSR Soc3a MGCSVSKKK Ca sensor
G2A glycine change to alanine Loss in
avirulence
7
RPM1MYC is degraded after inoculation with
avirulent P. syringae isolates, which trigger
LZ-NBS-LRR resistance genes
Hours post inoculation
Boyes et al., (1998) The Arabidopsis thaliana
RPM1 disease resistance gene product is a
peripheral plasma membrane protein that is
degraded coincident with the hypersensitive
response. 95, PNAS USA 15849-15854
8
AvrXa7 a nuclear targeted protein
PX086mx53 NLS- version
Resistant
Susceptible
NORMAL
avrXa7 over express
avrXa7 express
avrXa7 NLS-
NORMAL
avrXa7 over express
avrXa7 express
avrXa7 NLS-
Fig. 1.   AvrXa7 is a DNA-binding protein.
Double-stranded oligonucleotides were end labeled
with 32P, mixed with AvrXa7 or GST (glutathione
S-transferase), and subjected to polyacrylamide
electrophoresis. Arrow indicates position of
well.
Yang et al., (2000) The virulence factor AvrXa7
of Xanthomonas oryzae pv. oryzae is a type III
secretion pathway-dependent nuclear-localized
double-stranded DNA-binding protein.Proc Natl
Acad Sci U S A 159807
9
Guard Hypotheses