Chitinase cDNA Cloning and mRNA Induction by Fungal Elicitor, Wounding, and Infection

Abstract

Chitinase, which catalyzes the hydrolysis of β-1,4 N-acetylglucosamine linkages of the fungal cell wall polymer chitin, is a component of the inducible defenses of plants. We show that chitinase synthesis is stimulated in bean (Phaseolus vulgaris L.) cell suspension cultures treated with fungal cell wall elicitors and in hypocotyls in response to infection with the fungus Colletotrichum lindemuthianum. Chitinase cDNA clones were isolated by antibody screening of a λgt11 cDNA library containing sequences complementary to poly A⁺ RNA from elicited cells. The identity of these clones was confirmed by nucleotide sequence analysis and comparison of the deduced amino acid sequence with that determined for the amino-terminal sequence of bean chitinase. Elicitor causes a very rapid activation of chitinase transcription with a 10-fold stimulation after 5 minutes and 30-fold increase within 20 minutes. This leads to a marked, transient accumulation of chitinase transcripts with maximum levels 2 hours after elicitor treatment, concomitant with the phase of rapid enzyme synthesis. Chitinase transcripts also markedly accumulate in wounded and infected hypocotyls. Chitinase cDNA sequences hybridize to several genomic fragments suggesting there are several chitinase genes in the bean genome.