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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-138 - A novel polyketide biosynthetic enzyme complex produces dihydroxyhexanoic acid and regulates turgor pressure in appressoria

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Microbial infection strategies (pathogens & non-pathogens)
Many plant pathogenic fungi penetrate the host cuticle and cell wall mechanically using turgor pressure, particularly through specialized cells called appressoria. These cells accumulate osmolytes to generate turgor via osmosis, and develop a semipermeable cell wall that excludes molecules larger than water. While melanin is known to be essential for host penetration from appressoria, the mechanisms establishing wall semipermeability to prevent osmolyte leakage remain unclear. Here, we identify a novel polyketide biosynthetic enzyme complex, PKS2 and PBG13, as essential for forming the appressorial semipermeable barrier in both anthracnose fungi (Colletotrichum species) and the rice blast fungus (Magnaporthe oryzae). Deletion of these enzymes leads to increased cell wall permeability, resulting in reduced appressorial turgor and pathogenicity, without detectable effects on melanization. Ultrastructural analysis of the cell wall revealed morphological changes upon enzyme deletion, further supporting their role in barrier formation. In addition, these enzymes biosynthesize dihydroxyhexanoic acid polymers, which are critical for the semipermeable properties of the cell wall. Together, these findings establish a direct link between enzyme function and pathogen penetration ability, highlighting its importance in disease progression. Our findings reveal a previously uncharacterized mechanism of turgor generation in appressoria and identify potential new targets for disease control.