Contents. List of Contributors. 1 Emerging themes in plant pathogen interactions 1 NICHOLAS J. TALBOT. 2 Tobacco mosaic virus 27 JOHN PETER CARR

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1 Contents List of Contributors Preface x xii 1 Emerging themes in plant pathogen interactions 1 NICHOLAS J. TALBOT 1.1 Introduction Breaching the host cuticle MAP kinase signalling during infection-related development by fungi Invading host tissue Subverting host metabolism and defence Effector proteins deployed by pathogenic bacteria Host mimicry Perception of pathogens Recognition in gene-for-gene interactions and the guard hypothesis Genome-level analysis of pathogens Fungal and oomycete phytopathogen genomics The future 18 References 19 2 Tobacco mosaic virus 27 JOHN PETER CARR 2.1 Introduction Tobacco mosaic virus: virion and genome structure Genome structure and the taxonomy of TMV and related viruses The TMV virion Virion assembly Proteins encoded by the TMV genome Untranslated and regulatory RNA sequences within the TMV genome The establishment of TMV infection TMV replication and the synthesis of subgenomic mrnas The process of replication and subgenomic RNA synthesis The composition of the TMV replicase complex and its location in the infected cell Movement of TMV within the host Cell-to-cell movement of tobamoviruses Plasmodesmata and the viral movement protein Interactions of the TMV MP with host cell ultrastructure Interactions of the TMV MP with host proteins Are other virus-encoded proteins involved in cell-to-cell movement? 43

2 vi CONTENTS Systemic movement of tobamoviruses Virus movement and the phloem The movement protein The coat protein and systemic movement The replicase proteins, virus replication, and systemic movement The role of the host in the systemic movement of tobamoviruses Host reactions to TMV The susceptible host Chlorosis and vein clearing in systemically infected plants Mosaic symptoms in systemically infected plants: an effect of localized RNA silencing? Resistance to tobamoviruses The N resistance gene Resistance genes that are elicited by the tobamoviral CP Genes for resistance to tobamoviruses in tomato Genetically engineered resistance to tobamoviruses Future directions for TMV research: making an old foe into a new friend? 54 Acknowledgments 55 References 55 3 Infection with potyviruses 68 MINNA-LIISA RAJAMÄKI, TUULA MÄKI-VALKAMA, KRISTIINA MÄKINEN and JARI P.T. VALKONEN 3.1 Infection cycle (general summary) Architecture of virions Entry of virions into the cell, disassembly and assembly Translation and polyprotein processing Translation initiation Polyprotein processing RNA synthesis and viral genome replication Virus movement Intracellular movement Cell-to-cell movement Vascular movement Induction of symptoms Transmission Transmission by aphids Seed transmission Mechanical transmission Variability and evolution 82 Acknowledgments 84 References 85 4 The Ralstonia solanacearum plant interaction 92 CHRISTIAN BOUCHER and STÉPHANE GENIN 4.1 The pathogen A major plant pathogen with an unusually wide host range Taxonomical status of the species and infraspecific classification 92

3 CONTENTS vii R. solanacearum, a vascular pathogen that promotes xylem vessel occlusion Epidemiology and environmental survival Molecular studies of pathogenicity determinants Exopolysaccharide I Protein secretion systems Plant cell wall degrading enzymes and proteins secreted through the General Secretory Pathway The Type III secretion system (TTSS) Motility and attachment to host cell surfaces Swimming motility Type IV pili Regulation of pathogenicity PhcA, a global regulator controlling phenotypic conversion An atypical cell-sensing system A multicomponent network regulating virulence functions hrp gene activation in response to plant cell contact Genome-wide identification of candidate genes potentially involved in pathogenicity 105 Acknowledgment 106 References The Pseudomonas syringae bean system 113 SUSAN S. HIRANO and CHRISTEN D. UPPER 5.1 Introduction The system Population sizes of Pss on populations of leaf habitats Population processes: searching for causes of variability in pathogen population sizes Immigration and multiplication Emigration and death The four processes working together Enter the environment Enter the host Pss population sizes and the likelihood of disease development How does Pss cause brown spot lesions? Growth chamber assays Field experiments Germinating bean seeds Leaves Brown spot disease Growth chamber assays revisited Reconciliation Summary 132 References Fungal pathogenesis in the rice blast fungus Magnaporthe grisea 138 CHAOYANG XUE, LEI LI, KYEYONG SEONG and JIN-RONG XU 6.1 Introduction Life cycle of Magnaporthe grisea 138

4 viii CONTENTS 6.3 Conidium attachment and germination Attachment Germination Appressorium morphogenesis Surface recognition and appressorium initiation Appressorium maturation The role of camp signaling in surface recognition and appressorium initiation PMK1 regulates appressorium formation and maturation Hydrophobin MPG1 and surface recognition Other factors affecting appressorium formation Other mutants defective in appressorium morphogenesis Penetration Penetration peg Forces of penetration Turgor generation Other genes involved in appressorial penetration Infectious growth and lesion formation Infectious hyphae Phytotoxins produced by M. grisea Avirulence genes Nutritional requirements and metabolic activities during infectious growth Other mutants defective in infectious growth and lesion formation Genes specifically or highly expressed during infectious growth Conidiation Genomics studies Future perspectives 159 References The Ustilago maydis maize interaction 166 MARIA D. GARCIA-PEDRAJAS, STEVEN J. KLOSTERMAN, DAVID L. ANDREWS and SCOTT E. GOLD 7.1 Introduction Teliospore germination and meiosis Mating and dikaryon formation Penetration Infection structures in U. maydis Can haploid strains penetrate plant cells? Regulation of appressorium formation and plant penetration Potential role of lytic enzymes in penetration Colonization of maize tissue Proliferation of hyphae Interspecies signaling and colonization-specific fungal gene expression The biotrophic interface Gall formation and teliosporogenesis Developmental stages during gall formation and teliosporogenesis Genetic regulation of gall formation and teliosporogenesis Completion of sexual cycle in vitro Role of phytohormones in gall formation 191

5 CONTENTS ix 7.7 Survival Genetic diversity in U. maydis Host resistance Conclusions 194 Acknowledgements 195 References Blumeria graminis f. sp. hordei, an obligate pathogen of barley 202 MAIKE BOTH and PIETRO D. SPANU 8.1 Introduction Life cycle an overview Conidia and germination Surface perception and early events following contact with the surface Signal transduction during early development of B. graminis f. sp. hordei camp and PKA MAP kinases PKC G-proteins Penetration The haustorium Vegetative growth and sporulation Outlook 216 References The Phytophthora infestans potato interaction 219 PIETER VAN WEST and VIVIANNE G.A.A. VLEESHOUWERS 9.1 Introduction History of late blight Economic and social impact of Phytophthora plant pathogens Phytophthora infestans and its taxonomic position The disease cycle of Phytophthora infestans Molecular and cellular events during the disease cycle of P. infestans Release of zoospores from sporangia Encystment, germination, and appressoria formation Mating In planta gene expression The plant response Compatible interactions Incompatible interactions Race-specific resistance and the hypersensitive response Avirulence genes Resistance genes Non-host resistance Partial resistance Durable resistance Future perspectives 235 Acknowledgements 236 References 236 Index 243