Chitinases are thought to play a role in plant resistance to fungal pathogens by degrading the fungal cell wall, but few have been investigated to any great extent. The gene for a maize (Zea mays) chitinase “chitinase 2” previously reported to be induced by two ear rot pathogens in infected tissues from one maize inbred, was cloned from mRNA isolated from milk stage kernels of several different inbreds reported to be susceptible or resistant to ear rot pathogens. The chitinase gene sequence of some of the susceptible inbreds had frame shifts which would result in a nonfunctional protein as the catalytic site was altered. Other susceptible inbreds, and a few resistant inbreds genes were missing regions that would contribute to chitin binding. A putative functional clone from a resistant inbred was expressed in yeast, and produced a protein with chitinase activity against a 6 carbon polymer of N-acetyl glucosamine as indicated by MALDI-TOF analysis. The yeast-produced chitinase was also resistant to degradation by proteases from maize ear rot fungi, and enhanced antifungal activity of miconazole towards Fusarium graminearum. When introduced in maize callus transgenically, the callus expressing the chitinase 2 gene as indicated by visualization of activity against glycol chitin when separated using native polyacrylamide gel electrophoresis had significantly less growth of the ear rot pathogen, F. graminearium, than callus which did not express the gene. This information suggests susceptibility and resistance to ear rot pathogens is influenced not only by chitinase gene expression levels, but also by the sequence of putative resistance genes.

Functionality of a maize chitnase potentially inivolved in ear rot pathogen resistance

254th National Meeting (2017)

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