@talbotlabexeter
http://www.exeter.ac.uk/nicktalbot/
Cereal Killers:
Understanding How Fungi
Infect Plants
Nick Talbot New Fellows Seminar, The Royal Society, London July 10th 2014
Rice blast symptoms in Hunan Province, China - 2007
Neck Blast Hunan, China October 2007 Life Cycle of Magnaporthe oryzae Conidiophore
Conidium
Spore tip mucilage
Eruption
How is host immunity
suppressed ?
How do appressoria
form?
Germ tube
Tissue
colonisation
How is plant tissue
colonized?
Autophagic
cell death
How do appressoria
function?
Primary invasive hyphae
Penetration peg
Melanin-lined
appressorium
cell wall
Life Cycle of Magnaporthe oryzae Conidiophore
Conidium
Spore tip mucilage
Eruption
How do appressoria
form?
Germ tube
Tissue
colonisation
Autophagic
cell death
Melanin-lined
appressorium
cell wall
Primary invasive hyphae
Penetration peg
Conidia of Magnaporthe oryzae 10 µm
Appressorium forma0on in Magnaporthe oryzae De Jong et al., 1997 Nature 389:244-5
Veneault-Fourrey et al. 2006 Science 31: 580-3
Kershaw & Talbot, 2009 PNAS 106:15967-72
5 µm
Autophagy is required for nuclear degeneration, collapse of the
conidium and plant infection
WT
Δatg8
Veneault-Fourrey et al. 2006 Science 31: 580-3
WT
Δatg8
Life Cycle of Magnaporthe oryzae Conidiophore
Conidium
Spore tip mucilage
Eruption
Germ tube
Tissue
colonisation
Autophagic
cell death
How do appressoria
function?
Primary invasive hyphae
Penetration peg
Melanin-lined
appressorium
cell wall
How is cellular asymmetry generated in an
appressorium?
Bourett and Howard, 1990
An F-actin network forms around the appressorium
pore
LifeAct-RFP
Septins control cell shape in filamentous fungi
Septins form heterooligomers
Septin mutants have cell separation
defects
Wild type
cdc11ts
Septins can change cell shape
Localize at mother-bud neck
Spilliotis and Gladfelter 2011
Sep3-GFP
Septin ring around appressorial pore colocalizes
with an actin network
Lifeact
Sep3
10 µm
Septins organise a toroidal F-actin network at
the appressorium pore that is essential for plant
infection
The role of sep>ns in appressorium-­‐mediated cu>cle rupture Dagdas et al. 2012 Science 336:1590-95
Life Cycle of Magnaporthe oryzae Conidiophore
Conidium
Spore tip mucilage
Eruption
How is host immunity
suppressed ?
Germ tube
Tissue
colonisation
How is plant tissue
colonized?
Autophagic
cell death
Melanin-lined
appressorium
cell wall
Primary invasive hyphae
Penetration peg
Th Invading hyphae are surrounded by the host plant plasma membrane Fungal cytoplasm PtoxA-­‐tdTomato Plant membrane Merge L06b Mentlak et al. 2012 Plant Cell 24: 322-35
Effectors suppress plant
immunity
1
180
LysM LysM
•  Slp1 accumulates in the apoplast
•
•
•
•
•
Only expressed in planta
Two LysM domains
Binds chitin with high affinity
Competitively inhibits CEBiP PRR
Necessary for virulence
Mentlak et al., 2012 Plant Cell 24:322-35
•
•
Slp1 is glycosylated
N-Glycosylation of Slp1 is essential for
activity
Chen et al., 2014 Plant Cell online early
Summary
Many fungal pathogens develop specialized cells to infect plants called
appressoria
In rice blast disease, appressoria develop enormous pressure and use
physical force to rupture plant cuticle
Appressorium development is subject to cell cycle regulation and occurs
in response to physical cues from the host surface
Appressorium turgor generation is due to intracellular glycerol
accumulation
Septin-dependent re-modeling of the actin cytoskeleton is required for
appressorium function
Host cells remain intact as they are colonised by the fungus and plant
immunity is actively suppressed
Anotida Madzvamuse
Chandrasekhar Venkataraman
Vanessa Styles
University of Sussex
Anastasia Desyatova
Joseph Turner
Richard Wilson
University of Nebraska
Barbara Valent
Martha Giraldo
Kansas State University
Hiromasa Saitoh
Ryohei Terauchi
Iwate Rice Biotechnology Center
You-Liang Peng
China Agricultural University, Beijing
JinRong Xu
Purdue University
Bart Thomma
Wageningen University
Naoto Shibuya
Meiji University
Yasin Dagdas
Lauren Ryder
Wasin Sakulkoo
Xia Yan
Magdalena Urdiroz
Darren Soanes
Mick Kershaw
Miriam Oses-Ruiz
Yogesh Gupta
George Littlejohn
Tom Mentlak
Gero Steinberg
Halpin Trust