How Rice Blast Fungus Achieves Full Virulence

Plants use pattern recognition receptor to protect themselves from microbial pathogens. When the receptors recognize pathogen-associated molecular patterns (PAMPs), they activate signaling pathways that promote immunity. For instance, rice has a receptor called chitin elicitor binding protein (CEBiP) which recognizes the complex sugars excreted from the cell walls of fungal pathogens. However, some pathogens have mechanisms to get away with this front line of defense.

University of Exeter scientist Nicholas Talbot and colleagues found out that rice blast fungus (Magnaporthe oryzae) secretes a protein Secreted LysM Protein1 (Slp1) when invading rice cells. Their findings showed that Slp1 builds up between the fungal cell wall and the rice plasma membrane. The protein can also bind to chitin and block chitin-induced immune reactions. They also showed that Slp1 competes with CEBiP for binding in the complex sugars. Thus, Slp1 is important for rice blast fungus for full virulence including tissue invasion and lesion expansion.

Based on the results, the researchers suggest that Slp1 sequesters the complex sugars in chitin to prevent immunity in rice. Read the abstract at http://www.plantcell.org/content/24/1/322.abstract.