ARS | Publication request: Discovery and purification of a fungal protease secreted by Bipolaris zeicola that modifies maize seed endochitinase

Submitted to: Keystone Symposia
Publication Type: Abstract
Publication Acceptance Date: November 27, 2007
Publication Date: February 12, 2008
Citation: Naumann, T.A., Wicklow, D.T. 2008. Discovery and purification of a fungal protease secreted by Bipolaris zeicola that modifies maize seed endochitinase [abstract]. Keystone Symposia. Paper No. 220.

Technical Abstract: Healthy maize seeds have two basic endochitinases, chitA and chitB, with antifungal properties. A comparison of the isoenzyme profiles of symptomatic fungal-infested maize seeds, removed at harvest from ears that we wound inoculated in the late milk stage of maturity with one of several common ear-rotting fungal pathogens, revealed that activity from these two plant defense proteins is often diminished or absent. We further discovered that protein extracts from Bipolaris zeicola (Endo-3039) infested seeds could remove endochitinase activity from extracts of healthy seed, indicating the presence of a chitinase inhibitor. Further study determined that this effect was not due to a small molecule inhibitor but rather a fungal protein we have named chitinase modifying protease (Bzcmp). We have purified Bzcmp from fungal culture. It has a molecular weight of 54kDa, and an isoelectric point of 5.6. The protease converts purified endochitinases from 28kDa into truncated forms of 23kDa that no longer bind colloidal chitin. Current work focuses on cloning the putative fungal virulence protein and understanding the biological consequences of the interaction.