ARS | Publication request: The Zea mays ChitA Chitinase and its Modification by Secreted Proteins from Fungal Ear Rot Pathogens

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 23, 2009
Publication Date: July 23, 2009
Citation: Naumann, T.A., Wicklow, D.T. 2009. The Zea mays ChitA Chitinase and its Modification by Secreted Proteins from Fungal Ear Rot Pathogens [abstract]. XIV International Congress on Molecular Plant-Microbe Interactions. PS 5-307.

Technical Abstract: Zea mays (maize) seeds contain ChitA, a chitinase protein that contains a small, N-terminal domain (hevein) that allows the chitinase to bind insoluble chitin polymers with high affinity. We have discovered that maize ChitA chitinase is modified by a class of secreted fungal proteins termed chitinase modifying proteins (cmps). Fungal cmps are secreted by the ear rot pathogens Bipolaris zeicola (Holomorph = Cochliobolus carbonum) and Stenocarpella maydis (syn. Diplodia maydis). Biochemical experiments have demonstrated that fungal modified ChitA retains chitinase activity but has lost the ability to bind insoluble chitin. A previous report classified ChitA an antifungal protein. This classification was based on the ability of purified ChitA to inhibit the growth of some fungal plant pathogens in agar plate assays. We hypothesized that fungal modified ChitA, which no longer binds chitin, would have reduced potency in agar plate assays. We found that ChitA's ability to inhibit fungal growth in agar plate assays was unaffected by cmp facilitated modification and loss of chitin binding affinity. In summary, cmp proteins secreted by fungal ear rot pathogens modify maize ChitA chitinase resulting in loss of chitin binding abilities. Agar plate assays demonstrate that this modification does not alter ChitA antifungal activity and suggest that the in planta function of ChitA is more complex than the antifungal activity demonstrated in agar plate assays.