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Roots & Shoots’ September Guest blogger: Kaoutar El Mounadi, Ph.D., Dilip Shah Lab
Plants are continuously exposed to a plethora of potentially harmful pathogens. Fungal pathogens impose major constraints globally on agricultural production and food safety. Despite the continued release of resistant cultivars and chemical fungicides, an estimated 10-15% of crop yields are lost due to fungal infections.
In addition, narrow genetic diversity of commodity crops bred over the years by breeders limits their ability to respond if a new or re-emerging fungal disease takes hold. Safe and effective antifungal agents with novel fungus-specific mechanisms of action are urgently needed in agriculture.
Plants possess a dedicated immune system to fend off infection by fungal pathogens. They express a variety of host defense peptides which permit them to resist infection by these pathogens. Antifungal defensins are cysteine-rich plant defense effector proteins that are ubiquitously present in all plants and contribute to their innate immunity.
These small molecules exhibit a potent antifungal activity in vitro at micromolar concentrations against a diverse range of plant pathogenic fungi. Because of their potent antifungal activity, defensins can be exploited in agribiotechnological applications to generate disease resistant crops.
As a postdoctoral associate in Dr. Dilip Shah’s lab, my work is focused on deciphering the processes involved in the antifungal action of a plant defensin from Medicago truncatula called MtDef4.
MtDef4 effectively inhibits the growth of various fungal and oomycete pathogens including Fusarium graminearum (See figure 1), the causal agent of Fusarium Head Blight disease (FHB) on wheat and barley and an important producer of deoxynivalenol, a mycotoxin that poses a significant threat to the health of domestic animals and humans. MtDef4 is able to enter Fusarium graminearum cells (See figure 2) and bind the phospholipid phosphatidic acid (PA), a central node for lipid signaling in fungi through mechanisms that are still unclear.
Preliminary data from Dr. Shah’s lab have shown that ectopic expression of MtDef4 in transgenic wheat confers resistance to an obligate biotrophic fungal pathogen; Puccinia triticina, the causal agent of leaf rust disease (See figure 3).
I am interested in understanding how MtDef4 penetrates fungal cells, what its intracellular targets are, what sequence motifs are important for its internalization and its antifungal activity and how fungal pathogens might evade this defensin to cause successful colonization of host plants and disease.
This research will provide crucial insight into how to devise more effective strategies for genetic engineering of resistance to fungal and oomycete pathogens in transgenic plants and to ensure their mammalian and crop safety.
The theme of this year’s 16th annual Fall Symposium, Macroinfluence of Microogranisms: Host-Microbe Interactions and Inspired Technologies, relates to Kaoutar’s research in Dr. Shah’s lab.
The symposium, which will be held September 24-26, 2014, will highlight animal and plant pathogens, commensal microorganisms, microbiome scale investigations as well as research on the plethora of important technologies that have spawned from the study of host-microbe interactions.
For the most up-to-date information, please follow us at: Facebook & Twitter and use the hashtag #MarcoOfMicro
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