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Phenotypic and genetic evidence for tolerance to bacterial wilt in Arabidopsis plants

Dave BergerPlant Science DepartmentForestry and Agricultural Biotechnology Institute (FABI)University of PretoriaSlide2

Ralstonia solanacearum

Soil-borne vascular pathogen Wide host rangeSymptoms – wilting and necrosisSpecies complex (Fegan & Prior 2005)

Bacterial wilt

APSNETSlide3

Bacterial wilt on Eucalyptus trees

APSNET

AFRICA

Coutinho

TA, Roux J, Riedel KH,

Terblanche

J,

Wingfield

MJ (2000) First report of bacterial wilt caused by

Ralstonia

solanacearum

on eucalypts in South Africa. For

Pathol

30: 205-210

Roux

J,

Coutinho

TA,

Wingfield

MJ,

Bouillet

J-P (2000) Diseases of plantation Eucalyptus in the Republic of Congo. S

Afr

J

Sci

96: 454-456

Roux J,

Coutinho

TA,

Byabashaija

DM,

Wingfield

MJ (2001) Diseases of plantation Eucalyptus in Uganda. S

Afr

J

Sci

97: 16-18

BRAZIL

(2005) Susceptibility

to wilt associated with

Pseudomonas

solanacearum

among six species of Eucalyptus growing in equatorial Brazil. Austral Plant

Pathol

19: 71-76

CHINA

(

2009) Genetic diversity of

Ralstonia

solanacearum

strains from China. European Journal of Plant Pathology 125:

641-653

Fouche-Weich

J, Berger D,

Poussier

S,

Trigalet-Demery

D,

Coutinho

T (

2006) Molecular

identification of some African strains of

Ralstonia

solanacearum

from eucalypt and potato. Journal of General Plant Pathology 72: 369-373Slide4

Identify mechanisms of plant resistance to bacterial wilt

APSNET

STRATEGY

Screen Natural Diversity of Arabidopsis thaliana for resistance to bacterial wilt using Eucalyptus isolate of

Ralstonia

solanacearum

BCCF 402*

*

Fouche-Weich

J, Berger D,

Poussier

S,

Trigalet-Demery

D,

Coutinho

T (

2006) Molecular

identification of some African strains of

Ralstonia

solanacearum from eucalypt and potato. Journal of General Plant Pathology 72: 369-373Slide5

Dogma in

molecular plant pathologyResistance / : gene-for-gene interactionsImmunity

Tolerance : polygenic, QTLs of small effectSlide6

mock inoculated

Be-0

Kil-0

Nd-1

BCCF402

+ BCCF402

+ BCCF402

+ BCCF402

The

pathosystem

Ralstonia

solanacearum

BCCF 402 (from Eucalyptus)

vs

Arabidopsis thalianaSlide7

+ BCCF402

+ BCCF402

+ BCCF402

A curious result

Kil-0Slide8

Tolerance:

plant does not show a significant reduction in fitness despite high pathogen numbers in

planta

Resistance:

plant does not show a significant reduction in fitness

but severely restricts pathogen

numbers in

planta

Susceptibility:

plant shows a significant reduction in fitness and

has

high

pathogen numbers in

planta

Kover

and

Schaal

(2002) PNAS 99:11270-11274Slide9

Kil-0 does not show significant reduction in yield/fecundity in response to

R. solanacearum,in contrast to Be-0

Support for Tolerance hypothesisSlide10

What is the genetic basis of tolerance?

Cross-fertilization of Kil-0 and Be-0Slide11

CAPS markers confirm cross-fertilization ie

F1 progeny are hybrids

LweI

digestion of PCR products

(CAPS = cleaved amplified polymorphic sequences)

F

1

progeny were susceptible to

R.

solanacearum

BCCF402

Tolerance

is recessiveSlide12

Be-0

F

2 progeny

Kil-0

Kil-0 tolerance to

R.

solanacearum

conferred by

a single recessive gene

F

2

progeny segregate for

tolerance:

susceptibility

in a

1: 3 ratioSlide13

Kil-0 tolerance to

R. solanacearum linked to RRS1

Where in the Arabidopsis genome is the tolerance gene?

Hypothesis:

Tolerance conferred by allele of the RRS1 gene which confers R to a tomato isolate

F3

Tolerant F2 progeny

Susceptible F2 progeny

Kil-0

Kil-0

Be-0

Be-0Slide14

Tolerance in Kil-0 is allelic to resistance in Nd-1

mock

inoculated

inoculated

Be-0

Kil-0

Nd-1

F1

(Kil-0 X Nd-1)

Bacterial numbers

High

High

Low

High*

Kil-0 tolerance conferred by RRS1 or tightly linked geneSlide15

Susceptibility

Resistance

Col-5

Nd-1

( adapted from

da

Cunha et al. 2006)

R.

solanacearum

popP2

Be-0

Nd-1

Effector

triggered susceptibility

(ETS)

Effector triggered

immunity

(ETI)

popP2

RRS1-R

R.

solanacearum

Tolerance

Kil-0Effector triggered tolerance(ETT)popP2RRS1-RR. solanacearumSlide16

Susceptibity

Col-5

( adapted from

da

Cunha et al. 2006)

R.

solanacearum

popP2

Be-0

Effector triggered

susceptibility

(ETS)

Tolerance

Kil-0

Effector triggered

tolerance

(ETT)

popP2

RRS1-R

R.

solanacearum

Predict: popP2 mutant

ETT breaks down

R. solanacearumRRS1-RSlide17

mock inoculated

BCCF402

pLAFR6::

popP2

Kil-0

Be-0

BCCF402

ΔpopP2

BCCF402

ΔpopP2

Kil-0 tolerance requires

R.

solanacearum

popP2 effector

Supports hypothesis that Kil-0 tolerance conferred by RRS1 and not another linked geneSlide18

Tolerance

Kil-0

Effector triggered

tolerance

(ETT)

popP2

RRS1-R

R.

solanacearum

Resistance

Nd-1

Effector triggered

immunity

(ETI)

popP2

RRS1-R

R.

solanacearum

Do AA sequences of RRS1 or popP2 explain difference between ETI and ETT?Slide19

Do AA sequence differences in popP2 explain difference between ETI and ETT?

R.solanaceraum BCCF402 elicits ETI in Nd-1 and ETT in Kil-0.R.solanaceraum GMI1000 elicits ETI in Nd-1.Only 4 AA difference between PoP2 of BCCF402 and GMI1000Catalytic triad conservedAutoacetylated lysine conservedSlide20

RRS1

truncated in susceptible ecotypesOnly 8 AA difference between Nd-1 and Kil-0Do AA sequence differences in RRS1 explain difference between ETI and ETT?

 

Nd-1 (R )

 

% identity

Kil-0 (R )

98.9

Be-0 (S)

97.3

Col-0 (S)

91.8

1378 AASlide21

Conclusion: Gene-for-gene tolerance in Kil-0

R.solanacearum inoculation of Kil-0 plants:

Kil-0 did not wilt but had high bacterial numbers in

planta

Plant biomass yield, seed number, germination not reduced

Kil-0 response distinct from “resistant” ecotype Nd-1

Genetic evidence Kil-0 tolerance conferred by RRS1

Knockout/complementation evidence that Kil-0 requires

RRS1 – popP2 interactionSlide22

Nd-1

( adapted from da Cunha et al. 2006)

Kil-0

Effector triggered

tolerance

(ETT)

popP2

RRS1-R

R.

solanacearum

Model of Effector triggered tolerance (ETT)

Bergelson

lab

Rpm1 – fitness benefit at high inoculum levels

i.e. single gene tolerance (Genetics 2010)

Rps5 – no fitness benefit (New

Phytol

2009)

Nd-1

Effector triggered

immunity

(ETI)

popP2

RRS1-RR. solanacearumSlide23

Collaborators

Yves Marco &

Stephane

Genin

,

CNRS/INRA

, Toulouse, France

Katherine

Denby

, University of Warwick, UK

Sanushka

Naidoo

, Dept of Genetics, UP

Students

Liesl

van

der Linden

Jane

Bredenkamp

Acknowledgements

FundingNRF, South AfricaCNRS & Agropolis -South Africa exchange programmeSlide24
Slide25
Slide26

Multiplication of

R. solanacearum BCCF402 bacteria in A. thaliana

accessions Be‑0 and Kil-0 is hrp-dependent.

+ BCCF402

+ BCCF402

+ BCCF402

+ BCCF402

hrp

hrp

Be-0

Kil-0

Be-0

Kil-0

(

Hrp

cluster encodes type III secretion system)

By: briana-ranney
Views: 73
Type: Public

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Phenotypic and genetic evidence for tolerance to bacterial - Description


Dave Berger Plant Science Department Forestry and Agricultural Biotechnology Institute FABI University of Pretoria Ralstonia solanacearum Soilborne vascular pathogen Wide host range ID: 332283 Download Presentation

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