PLANT PHYSIOLOGY , Vol 111, Issue 4 1135-1144, Copyright © 1996 by American Society of Plant Biologists
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PLANT-MICROBE AND PLANT-INSECT INTERACTIONS |
Proteolytic Processing of Class IV Chitinase in the Compatible Interaction of Bean Roots with Fusarium solani
J. Lange, U. Mohr, A. Wiemken, T. Boller and R. Vogeli-Lange
Botanisches Institut, Universitat Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland
Three chitinase isoenzymes, PvChiE, PvChiF, and PvChiG (molecular masses
29, 28, and 27 kD, respectively), were purified from bean (Phaseolus
vulgaris L. cv Saxa) roots infected with the fungal pathogen Fusarium
solani f. sp. phaseoli, and their amino acid sequence was partially
determined. All sequences from all three isoenzymes exactly matched deduced
amino acid sequences of the bean class IV chitinase PvChi4, formerly called
PR4. The N terminus of PvChiF mapped to the hinge region, and the N
terminus of PvChiG mapped to the catalytic domain of PvChi4. The N terminus
of PvChiE was blocked. The appearance of PvChiE, PvChiF, and PvChiG
correlated with an increase in protease activity in infected roots, and
they could be generated in vitro by mixing extracts with high protease
activity with extracts containing high amounts of PvChi4. Extracts from
infected roots prepared in the presence of protease inhibitors also
contained the processed forms of PvChi4, indicating that processing
occurred in planta and not as an artifact of extraction. Processing of
PvChi4 was not detected in incompatible interactions with a nonhost strain
of F. solani and in symbiotic interactions with Glomus mosseae, and thus
may be important only in compatible interactions with F. solani.
