Title: Antimicrobial peptide inhibition of fungalysin proteases that target plant type 19 Family IV defense chitinases Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 8, 2013
Publication Date: N/A
Technical Abstract: Cereal crops and other plants produce secreted seed chitinases that reduce pathogenic infection, most likely by targeting the fungal chitinous cell wall. We have shown that corn (Zea mays) produces three GH family 19, plant class IV chitinases, that help in protecting the plant against Fusarium and Bipolaris species. The Z. mays chitinases are comprised of two domains; a small N-terrminal hevein domain that contains a chitin binding region, and a C-terminal chitinase enzyme domain. The hevein and chitinase domains are joined by a polyglycine bridge, the composition of which is plant specific. The enzyme domain is a type 19 chitinase that we know cleaves chitobiose repeat units from the non-reducing end of chitin oligosaccharides. Several fungal pathogens secrete proteases that target the plant class IV chitinases, thereby partially inactivating this mechanism of defense. We have shown that fungalysins, Zn-containing secreted proteases produced by Fusarium sp., cause the cleavage of both corn and Arabidopisis defense chitinase at a well-defined Gly-Cys site between the hevein and catalytic domains (Naumann et al, J. Biol. Chem, 2012). Furthermore, we have identified a hydrolytic protease from Bipolaris zeicola that modifies the inter-domain polyglycine bridge of ChitA. Furthermore, we have identified a hydrolytic protease from Bipolaris zeicola that modifies the inter-domain polyglycine bridge of ChitA. The inhibition of fungalysin proteases by small peptides called WAMPs, also known to promote fungal resistance, will be discussed. The WAMPs are homologous with the N-terminal hevein domain, suggesting a competitive mode of inhibition.