Tête à tête inside a plant cell: establishing compatibility between plants and biotrophic fungi and oomycetes

Abstract

Contents Summary 699 Introduction 700 Plant cell entry control 700 The plant–biotroph interface 703 Biotroph effectors 708 Plant factors for compatibility 711 Future directions and opportunities 713 Acknowledgements 713 References 713 Summary ‘Compatibility’ describes the complementary relationship between a plant species and an adapted pathogen species that underlies susceptibility and which ultimately results in disease. Owing to elaborate surveillance systems and defence mechanisms on the plant side and a common lack of adaptation of many microbial pathogens, resistance is the rule and compatibility the exception for most plant–microbe combinations. While there has been major scientific interest in ‘resistance’ in the past decade, which has revealed many of its underlying molecular components, the analysis of ‘compatibility’, although intimately intertwined with ‘resistance’, has not been pursued with a similar intensity. Various recent studies, however, provide a first glimpse of the pivotal players and potential molecular mechanisms essential for compatibility in both the plant and parasite partners. In this review we highlight these findings with a particular emphasis on obligate biotrophic and hemibiotrophic fungal and oomycete pathogens and discuss novel strategies that might help to uncover further the molecular principles underlying compatibility to these highly specialized pathogens.

Live-Cell Imaging Reveals Periarbuscular Membrane Domains and Organelle Location in Medicago truncatula Roots during Arbuscular Mycorrhizal Symbiosis

“…Haustoria are surrounded by a plant extrahaustorial membrane (EHM) that is believed to mediate transport of nutrients to the pathogen (O'Connell and Panstruga, 2006). Studies of the interaction between Arabidopsis and a powdery mildew pathogen found that plasma membrane markers, including AtPIP2a, did not localize to the EHM but did localize to the haustorial neck (Koh et al, 2005).…”

Involvement of Abscisic Acid in the Coordinated Regulation of a Stress-Inducible Hexose Transporter (VvHT5) and a Cell Wall Invertase in Grapevine in Response to Biotrophic Fungal Infection

“…The ABA-induced increase in cwINV would aid fungal nutrition, as biotrophic fungi preferentially take up hexose sugars rather than Suc (O'Connell and Panstruga, 2006), although certain biotrophic pathogens may secrete their own invertase to achieve this goal (Voegele et al, 2006). ABA has also been demonstrated to have a suppressive effect on the salicylic acid-dependent defense pathway that normally promotes resistance against biotrophic pathogens (Mohr and Cahill, 2007).…”

“…Both powdery mildew and downy mildew are obligate biotrophs that acquire nutrients via specialized feeding structures called haustoria, which are formed within host cells after penetration through the cell wall. In the case of powdery mildew, this involves the penetration of cells within the epidermal layer, whereas downy mildew initially invades via the stomates and forms haustoria within mesophyll cells (O'Connell and Panstruga, 2006).…”

Downy Mildew Resistance in Arabidopsis by Mutation of HOMOSERINE KINASE

“…The molecular mechanisms underlying disease susceptibility, and more specifically the role of host-specific processes that sustain pathogen development and growth, are still largely unknown. In recent years, genetic studies on the model plant Arabidopsis thaliana have resulted in the identification of a number of genes that are involved in susceptibility to biotrophic pathogens (Vogel and Somerville, 2000;O'Connell and Panstruga, 2006). Mutations in the POWDERY MILDEW RESISTANT genes PMR6 and PMR5, encoding a pectate-lyase and a protein of unknown function, respectively, result in plants with an altered cell wall that is thought to underlie their phenotype (Vogel et al, 2002(Vogel et al, , 2004.…”