Plant Pathology Seminar Series
“Mechanisms of plant defense to fungal pathogens”
Lu Liu
Unlike animals that are mobile and have a somatic adaptive immune system, plants respond to fungal pathogen infection by
innate defenses (Jones and Dangl 2006). The epidermal cell layer of aerial plant parts, often covered in a waxy cuticle, is the
first line of defense against invading fungi. Besides that, plants are able to recognize pathogen-derived elicitor molecules that
trigger a number of induced defenses in plants since fungal pathogens can degrade the cuticle and penetrate the epidermis.
Microbial elicitors constitute a broad array of compounds, including different oligosaccharides, lipids, peptides, and proteins
(Montesano et al. 2003). Plants also generate endogenous elicitors due to the damage caused by microbes, which are,
therefore, called damage-associated molecular patterns (DAMPs) (Wu et al. 2014). At the same time, plants encode hundreds
of receptors to recognize different types of elicitors and activate signaling pathways (Okmen and Doehlemann 2014). Once
the immunity system is activated, a series of defense responses occur, including plant cell wall strengthening, secondary
metabolite production, reactive oxygen species (ROS) production, defense-related protein synthesis, and hypersensitive
reaction (HR) (Howell and Davis 2005; Huckelhoven 2007; Zhang et al. 2012). It has been suggested that effective defense
against biotrophic fungi largely relies on programmed cell death (PCD) in the host. In contrast, PCD benefits the development
of necrotrophic fungal pathogens (Glazebrook 2005; Qiu et al. 2015; Vargas et al. 2012). Understanding plant defense
mechanisms at the molecular level can help us better manipulate plant resistance and develop disease management
strategies.
4:10 pm | Monday, November 2 | Johnson Hall 343
Plant Pathology 515, Fall, 2015
References:
Dangl, J and Jones, J. 2001. Plant pathogens and integrated defense responses to infection. Nature 411:826 –
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Glazebrook, J. 2005. Contrasting mechanisms of defense against biotrophic and necrotrophic pathogens. Annu.
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Howel, J., and Davis M. 2005. Plant defense mechanisms against fungal pathogens: polygalacturonase inhibitor
proteins. Can. J. Plant Pathol. 27: 5-15.
Huckelhoven, R. 2007. Cell wall-associated mechanisms of disease resistance and susceptibility. Annu. Rev.
Phytopathol. 45:101-27.
Jones, J., and Dangl, J. 2006. The plant immune system. Nature 444:324-329.
Montesano, M., Brader, G., and Palva, E. 2003. Pathogen derived elicitors: searching for receptors in plants. Mol.
Plant Pathol. 4: 73-79.
Okmen, B., and Doehlemann, G. 2014. Inside plant: biotrophic strategies to modulate host immunity and
metabolism. Curr. Opin. Plant Biol. 20: 19-25.
Qiu, W., Feechan, A., and Dry, I. 2015. Current understanding of grapevine defense mechanisms against the
biotrophic fungus (Erysiphe necator), the causal agent of powdery mildew disease. Hortic. Res. 2: 15020.
Vargas, W., Martin, J., Rech, G., Rivera, L., Benito, E., Diaz-Minguez, J., Thon, M., and Sukno, S. 2012. Plant
defense mechanisms are activated during biotrophic and necrotrophic development of Colletotricum
graminicolain maize. Plant Physiol. 158: 1342-1358.
Wu, S., Shan, L., and He, P. 2014. Microbial signature-triggered plant defense responses and early signaling
mechanisms. Plant Sci. 228: 118-126.
Zhang, H., Wang, C., Cheng, Y., Chen, X., Han, Q., Huang, L., Wei, G., and Kang, Z. 2012. Histological and
cytological characterization of adult plant resistance to wheat stripe rust. Plant Cell Rep. 31: 2121-2137.