Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 1999
Publication Date: N/A
Technical Abstract: Chitinases degrade a major component of fungal cell walls and are involved in the defense mechanisms of plants against pathogens. Here we report the isolation and characterization of a cDNA and a gene encoding a basic chitinase in alfalfa. The structural gene consists of a single open reading frame encoding a polypeptide of 327 amino acids with a 23 amino acid N- terminal signal peptide, and a 39 amino acid cysteine-rich domain. Alfalfa basic class I chitinase is encoded by a small gene family and is expressed in an age-dependent and tissue-specific manner. Transcripts accumulated to a high level in roots, were less abundant in stems, nodules, and flowers, and non-detectable in a mixture of leaves of different ages. However, separation of leaves showed an age-dependent accumulation of chitinase transcripts: highest in old leaves, less in middle-aged leaves, and non- detectable in the youngest leaves. Fungal infection of alfalfa plants resulted in increased levels of the basic chitinase mRNA in leaves of all ages. The increase of chitinase transcript level in infected leaves paralleled development of disease symptoms. The 5' flanking region of the chitinase gene confers induction of reporter gene activity in root tips and leaves of transgenic plants in response to nematode and fungal infections. The reporter gene activity pattern in infected leaves of transgenic plants was consistent with that observed for the native gene.