Infection Strategies and Pathogenicity of Biotrophic Plant Fungal Pathogens

Abstract

Biotrophic plant pathogenic fungi are widely distributed and are among the most damaging pathogenic organisms of agriculturally important crops responsible for significant losses in quality and yield. However, the pathogenesis of obligate parasitic pathogenic microorganisms is still under investigation because they cannot reproduce and complete their life cycle on an artificial medium. The successful lifestyle of biotrophic fungal pathogens depends on their ability to secrete effector proteins to manipulate or evade plant defense response. By integrating genomics, transcriptomics, and effectoromics, insights into how the adaptation of biotrophic plant fungal pathogens adapt to their host populations can be gained. Efficient tools to decipher the precise molecular mechanisms of rust–plant interactions, and standardized routines in genomics and functional pipelines have been established and will pave the way for comparative studies. Deciphering fungal pathogenesis not only allows us to better understand how fungal pathogens infect host plants but also provides valuable information for plant diseases control, including new strategies to prevent, delay, or inhibit fungal development. Our review provides a comprehensive overview of the efforts that have been made to decipher the effector proteins of biotrophic fungal pathogens and demonstrates how rapidly research in the field of obligate biotrophy has progressed.

Mycorrhizal Association and Plant Disease Protection: New Perspectives

“…In summary, resistance mediated by R genes is specific to certain races of the pathogen and effective against biotrophic and hemibiotrophic parasites. On the other hand, quantitative resistance provides a means for controlling biotrophic, hemibiotrophic, and necrotrophic pathogens, being effective against several races of a pathogen, providing broad-spectrum resistance, or in some specific cases, effective against several pathogens [97][98][99][100][101][102][103].…”

The haustorium: The root of biotrophic fungal pathogens

“…Monokaryotic haustoria are terminal intercellular hyphae without morphological differentiation and have a septum near the penetration site ( Gold and Mendgen, 1984 , 1991 ; Harder and Chong, 1984 ). Prior to the formation of haustorium, rust fungi dikaryotic urediospores germinate on host plant epidermis and form germ tubes which sense the host cuticle topography and develop appressoria above the stomata to penetrate the intercellular spaces of the mesophyll, potentially bypassing epidermal defense responses ( Mapuranga et al, 2022 ). Penetration occurs through stomata by the penetration hyphae into the substomatal spaces where the fungus differentiates into substomatal vesicles and elongates into an intercellular hypha which comes into contact with the host mesophyll cells and develops haustorial mother cells ( Mendgen et al, 2000 ; Voegele et al, 2009 ).…”

“…Most powdery mildew fungal species use their appressoria to directly penetrate into cuticle and cell wall of the host plant to colonize exclusively the epidermal cells of the host plant ( Mapuranga et al, 2022 ). Successful penetration results in the development of a penetration peg that penetrates directly into the epidermal cuticle of the host plant leading to the formation of haustoria which invaginates the host plasma membrane ( Bushell and Bergquist, 1974 ).…”

“…This suggests the separation of the haustorial mother cell and haustorium from the hyphae which probably facilitates the development of independent transcriptional and metabolic programs in these cells (Polonio et al, 2021). Most powdery mildew fungal species use their appressoria to directly penetrate into cuticle and cell wall of the host plant to colonize exclusively the epidermal cells of the host plant (Mapuranga et al, 2022). Successful penetration results in the development of a penetration peg that penetrates directly into the epidermal cuticle of the host plant leading to the formation of haustoria which invaginates the host plasma membrane (Bushell and Bergquist, 1974).…”

Harnessing genetic resistance to rusts in wheat and integrated rust management methods to develop more durable resistant cultivars

“…Establishing a dynamic parasitic relationship between the biotrophic fungi and the host is the foundation for the development of the pathogen in the host plant. In order to infect the host plant successfully, rust pathogens suppress PTI components by secreting virulence factors called effectors into the host cells through the haustoria and hyphae resulting in effector-triggered susceptibility (ETS) (Martel et al, 2021;Mapuranga et al, 2022a;Mapuranga et al, 2022b). The plants in response developed a second layer of innate immunity known as effector-triggered immunity (ETI), in which the plant resistance proteins recognize corresponding avirulence factors and set off a powerful defensive response.…”