To my beloved grandparents, who were always proud of me.

178 Pages·2014·4.08 MB·English

To my beloved grandparents, who were always proud of me.

Precise knowledge of self and precise knowledge of the threat leads to victory.
-The Art of War, by Sun Zi.
Promotor: Prof. Dr. ir. Monica Hӧfte
Co-promotor: Dr. ir. David De Vleesschauwer
Laboratory of Phytopathology, Department of Crop Protection,
Ghent University

Dean: Prof. Dr. ir. Guido Van Huylenbroeck

Rector: Prof. Dr. Anne De Paepe
Global switches and fine-tuning: the multifaceted role of
plant hormones in regulating rice immunity against the
leaf blight pathogen Xanthomonas oryzae pv. oryzae

Jing XU

Thesis submitted in fulfillment of the requirements for the degree of Doctor
(PhD) in Applied Biological Sciences
Dutch translation of the title:
Globale regulatoren en fijnregeling: de veelzijdige rol van plantenhormonen in de
resistentie van rijst tegen de bladpathogeen Xanthomonas oryzae pv. oryzae.

Cover illustration:
Interpretation of the battlefield where plant hormones, rice and Xanthomonas oryzae
pv. oryzae are the players.

Cite as:
Xu J (2014) Global switches and fine-tuning: the multifaceted role of plant hormones
in regulating rice immunity against the leaf blight pathogen Xanthomonas oryzae pv.
oryzae. PhD thesis, Ghent University, Belgium

ISBN number: 978-90-5989-731-1

The author and the promotor give the authorization to consult and to copy parts of
this work for personal use only. Every other use is subject to the copyright laws.
Permission to reproduce any material contained in this work should be obtained from
the author.
Members of the jury

Prof. Dr. ir. Monica Hӧfte (Promotor)
Department of Crop Protection
FBW, Ghent University

Dr. ir. David De Vleesschauwer (Co-promoter)
Department of Crop Protection
FBW, Ghent University
Prof. Dr. ir. Peter Bossier (Chairman)
Department of Animal Production
FBW, Ghent University

Dr. ir. Tina Kyndt (Secretary)
Department of Molecular Biotechnology
FBW, Ghent University

Dr. Danny Vereecke
Department of Applied Biosciences
FBW, Ghent University

Dr. Peter Bakker
Institute of Environmental Biology
Utrecht University, the Netherlands

Dr. Vittorio Venturi
Group of Bacteriology and Plant Bacteriology
International Centre for Genetic Engineering and Biotechnology, Trieste, Italy

Acknowledgements
After four years and nine months, I found purchasing the PhD degree is like making a
journey to me. With a lot of guidance, help, encouragements and companionship
during this 'journey', finally I reach this stage.
First of all, I would like to thank my promoter Prof. Dr. ir. Monica Hӧfte for accepting
me to this international Lab and for her support during my PhD. I’m always amazed
by how knowledgeable Prof. Hӧfte is. I learned a lot from her, especially about being
scientific and critical in doing research. I’m also very grateful to my co-promoter, Dr.
ir. David De Vleesschauwer for guiding me into the wonderful rice immunity world.
During the past several years, David taught me everything about how to become a
PhD, including learning laboratory technics, designing experiments, analyzing data,
writing papers and so on. Thank you, Monica and David, for all the guidance and
support, and for all the efforts you did for me.
I would like to thank all the jury members (Prof. ir. Peter Bossier, Dr. ir. Tina Kyndt,
Dr. Danny Vereecke, Dr. Peter Bakker and Dr. Vittorio Venturi) for their valuable
comments and suggestions, which made my thesis better. Special thanks to several
collaborators: Dr. Hitoshi Sakakibara, Dr. Vittorio Venturi and Prof. Ya-Wen He,
who helped me out in some tests for this thesis. I'm very grateful to Prof. Guo-An
Zhang, my promoter during the master study. He promoted me to purchase PhD
study in aboard and concerns about my work and life all the time. Thank you, Prof.
Zhang.
I’m deeply indebted to my lovely ‘office-mates’: Ilse, Nathalie and Soren. Ilse, you
helped me so much in every aspect, from my work to my life. Nathalie, my ‘twin
sister’, you made me more social in the lab and made my stay in Belgium much more
joyful. Soren, you have been giving me wise suggestions all the time. Thank you all
for your precious friendship, help and encouragements. we shared so many happy
and sad moments together, and We made our office the best ever! I would like
express my deepest gratitude to many other friends in our Lab: Khuong, my first
friend in Gent, I’m so glad that I met you here. I wish you all the best! Soraya, your
enthusiasm and wisdom in work, as well as in life, always touches me. I enjoyed
every inspiring talk with you and I hope we can meet again in future. Huang, you
taught me a lot in bacteriology and helped me much in the lab. You and your wife
offered much care to me, especially during my thesis writing period. Thank you!
Nadia, thank you for all the help in dealing with administrative work. Evelien (De
Waele), you helped me so much in finalizing my practical work and you are an angle
to me! Jonas, Lieselotte and Evelien (Van Buyten), I'll never forget all the 'happy'
time we spent together in the old greenhouse and all the 'fun' trips to ILVO. Jasper,
thank you for reminding me every holiday. I'm also very thankful to all the other
(ex)colleagues: Lieve, Zabih, Katrien, Lien B, Lien T, Silke, Pauline, Vincent, Osvaldo,
Feyi, Nam......, thanks a lot !
I must thank my dear chinese friends: Yu Yun, Gao Ting and Ni Na, thank you for
always being there for me and for supporting every of my decisions. Sheng Jing and
Li Min, you two have been taking care of me as my elder sisters. Ke Ji, thank you for
designing the cover of my thesis. Wang Xiang, thanks for helping me with the layout
of this thesis. Hai Dong, Li Fan and Chen An, you cooked a lot for me and brought
me much joy during my thesis writing period. Tong Qing, Yuan Yuan, Ji Sheng, Gu
Yue, Gao Yun, Xiao Xi, Qi Lu, Bai Meng, Li Yang......, Thank you so much for all
the help, encouragements and companionship.
My lovely aunts, sister and brother in law, thank you for being supportive all the
time, I own you a lot! My little nephew, you bring so much joy to me. My great
parents, who only care about my happiness in life rather than achievements in work,
taught me to be a strong and generous person. Without your lessons, unconditional
love and support, I would never reach this PhD. Dad and Mom, I love you!
At the end, I would like to thank the Chinese Scholarship Council (CSC) for awarding
me the PhD scholarship, which enabled my 'journey' to start.
Contents

List of Abbreviations

Chapter 1 Problem statement and thesis outline 1
Chapter 2 General introduction 7
Chapter 3 Making sense of hormone-mediated defense networking: from rice to 29
Arabidopsis
Chapter 4 Abscisic acid promotes susceptibility to the rice leaf blight pathogen 45
Xanthomonas oryzae pv. oryzae by suppressing salicylic acid-
mediated defenses
Chapter 5 Cytokinin attenuates rice immunity against the bacterial leaf blight 67
pathogen Xanthomonas oryzae pv. oryzae by activating Target of
Rapamycin signaling
Chapter 6 Phytohormone-mediated interkingdom signaling shapes the outcome 89
of rice- Xanthomonas oryzae pv. oryzae interactions
Chapter 7 General discussion and future perspectives 115

Summary 133
Samenvatting 135
References 137
Curriculum vitae 163
List of Abbreviations

ABA: abscisic acid
AHLs: N-acyl homoserine lactones
AI: autoinducer
BLB: bacterial leaf blight
BR: brassinosteroid
BTH: benzothiadiazole S-methylester
CK: cytokinin
DAMPs: damage-associated molecular patterns
DF: diffusible factor
DSF: diffusible signal factor
EPS: extracellular polysaccharides
ET: ethylene
ETI: effector-triggered immunity
ETS: effector-triggered susceptibility
Flu: fluridone
GAs: gibberellins
HR: hypersensitive response
IAA: indole-3-acetic acid
IAAsp: indole-3-acetylaspartic acid
IPT: isopentenyl transferase
ISR: induced systemic resistance
JA: jasmonic acid
LPS: lipopolysaccharides
LRR: leucine-rich repeat
M(A)PK: mitogen-activated protein kinase