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haplotype
host of origin
resistance gene
Couch et al. 2005
Magnaporthe oryzae
Signaling on the leaf surface
positive regulation negative regulation
stage of
development signal
receptor
+
adenyl
cyclase
MAPK
MAPK
transcription
factor
X
heterotrimeric
G protein
dissociation
protein kinase
spore tip mucilage
Howard and Valent 1996
Cosegregation of the appressorium
deficiency phenotype
with the mpg1::Hph deletion allele.
WT
mpg1-
hygS
hygR
hygS
MPG1 directs formation of the
hydrophobic rodlet layer of conidia.
WT
mpg1-
hygR
WT mpg1MPG1+
MPG1+
Reintroduction of MPG1
restores pathogenicity,
appressorium development and
cell surface hydrophobicity
mpg1-;hygR
MPG1-;hygS
Importance of melanized appressoria
Howard, R
chitin
WT
albino
melanin
appressorium
pore
Howard and Valent 1996
Penetration and invasion
penetration site
Dean et al, 2005
melanin biosynthesis
Howard and Valent 1996
Collapse
high concentration
of non-permeable
solute
conidium
germ tube
appressorium
sonicated cells
Howard and Valent 1996
Appressoria build turgor during
incubation
Howard et al., 1991
The transcription factor MST1 is important for
penetration peg formation
homeodomain
WT
Zn finger
mutants
Park et al. 2004
The transcription factor MST1 is important for
penetration peg formation
mst1WT
appressoria
can form
can’t
penetrate
no peg
From Park et al 2004
Fungal avirulence genes
and others
AVR-Pi-ta
Lauge and de Wit 1998
four Avr genes;
Avr2, Avr4, Avr4E and
Avr9
four extracellular
protein (Ecp) genes;
Ecp1, Ecp2, Ecp4 and
Ecp5).
M. oryzae Pi-ta / AVR-Pi-ta
Fig. 2. Genotype-specific HR in rice seedlings induced by M.grisea carrying AVR-Pita. Sparse HR flecking is seen in Pi-tacontaining rice seedlings (A) Yashiro-mochi and (B) YT14, as expected. In contrast, typical symptoms of rice blast disease
are seen in susceptible rice seedlings (C) Nipponbare and (D) YT16. Representative leaves are shown from rice seedlings
germinated in plant nutrient medium and infected with avirulent M.grisea strain 4360-R-62 (see Materials and methods for
details). Shown at 4 days after inoculation
Jia et al. 2000
Pi-ta
YM
YT14
resistant
pi-ta
Ni
YT16
susceptible
Pi-ta dependent resistance response
Genotype specific response
Intracellular (metalloprotease)
direct interaction with Pi-ta
Fig. 3. AVR-Pita176 is an elicitor. (A) AVR-Pita polypeptides tested in the transient assay. The white
region indicates the putative secretory signal sequence, the gray region indicates the putative pro-protein
domain and the hatched region indicates the putative protease motif. The black region indicates the
putative mature protein. The number of amino acids missing from the N-terminus is indicated. GUS
activity is indicated by ‘+’, whereas decreased GUS activity is indicated by ‘–’. (B) Representative rice
seedlings showing GUS activity. Two-leaf Pi-ta (Yashiro-mochi and YT14) and pi-ta (Nipponbare and
YT16) seedlings were co-bombarded with 35S/Adh1-6::AVR-Pita176 and 35S::uidA. Leaves were
assayed histochemically for GUS activity and cleared in 70% ethanol to visualize GUS staining.
(C) RNA gel blot analysis of AVR-Pita expression in the transient assay. YT14 (Pi-ta) and YT16 (pi-ta)
were co-bombarded with the 35S/Adh1-6::AVR-Pita176 and 35S::uidA plasmids. Leaf tissue was
harvested 2 days after bombardment. Poly(A)+ mRNA was then extracted, blotted to Hybond-N and
hybridized with a radiolabeled AVR-Pita176 probe. The AVR-Pita transcript is indicated. Similar loading
was verified before blotting by visualizing mRNA in the gel stained with ethidium bromide.
Jia et al. 2000
Magnaporthe oryzae
is also a root pathogen
hydrophobic
surface
roots
a−c, GFP-tagged M. grisea (Guy11) forms classical appressoria (AP)
on a hydrophobic surface (a) and simple hyphopodia (HY) and
infection pegs (IP) on rice roots (cultivar CO39) (b, c). d−k, Guy11infected barley (d, e, j, k) and rice (f−i) roots stained with chlorazole
black E showing: dark runner hyphae (RH) and simple hyphopodia (d,
e); bulbous infection hyphae invading epidermal cells (f);
microsclerotia (previously reported in culture). Scale bar, 25 µm.
Sesma and Osbourn
Sesma and Osbourn
Pigment and cAMP are not required
albino
cAMP-
albino
a, Roots of barley seedlings (cultivar
Golden Promise) that have been
mock-inoculated or infected with the
M. grisea wild type (WT) or mutant
(mel, cpkA) strains. b, Formation of
hyphopodia-like structures (HY) and
invasive growth within epidermal cells
during the early stages of infection.
Scale bars, 25 µm (b), 40 µm (c).
cAMPSesma and Osbourn
M. oryzae can move systemically
from roots to leaves
Roots of barley seedlings (cultivar Golden Promise) that
have been mock-inoculated or infected with the M.
grisea wild type (WT) strain.. c, M. grisea penetrates
the stele. Confocal imaging of radial and longitudinal
sections of a three-week-old rice seedling (cultivar
Nipponbare) infected with GFP-tagged M. grisea (strain
Guy11). Scale bars, 25 µm (b), 40 µm (c).
Sesma and Osbourn
M. oryzae can
move
systemically
from roots to
leaves
Pi-CO39(t)mediated
specific
disease
resistance
operates in
rice roots
a−c, Four-week-old root-infected rice seedlings (cultivar Nipponbare) showing
disease symptoms on the leaf (upper box) and collar (lower box) (a). Disease
symptoms on the collar (b) and stem (c) with confocal images showing GFPexpressing M. grisea Guy11 in the diseased areas and also in the vascular tissue
of the leaf and stem. d−f, Pi-CO39(t)-mediated specific disease resistance
operates in rice roots. Confocal microscopy of compatible (d, e) and
incompatible (f) interactions. Cultivar, cv. Scale bar, 40 µm.
Sesma and Osbourn