ARS | Publication request: CHARACTERIZATION OF ACIDIC CHITINASES FROM CULTURE MEDIUM OF SWEET ORANGE CALLUS TISSUE

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 31, 1998
Publication Date: N/A

Interpretive Summary: Plants have proteins and enzymes (pathogenesis-related proteins) that aid in resisting insects and diseases. Citrus pathogenesis-related proteins have been studied by our laboratory for the last few years to determine which of these may be useful in developing improved varieties. Chitinases are a part of the plant's resistance mechanisms and act to breakdown chitin which makes up a large part of the fungal cell walls and insect skeletons. Chitinases can either be secreted outside of the plant cell or be held in reserve inside of the cell until used to ward off pests. It is important to identify those proteins secreted outside of the cell because these proteins are thought of as a first-line defense and enhance the plants resistance response. The research reported here describes two chitinases that are thought to be secreted outside of the cell. Information on the chemistry of the proteins and the amino acid sequences is presented for comparison with other plant chitinases.

Technical Abstract: Two acidic proteins (ACHCM-1 and ACHCM-2) that exhibited chitinase (E.C. 3.2.1.14) and chitosanase (EC 3.2.1.99) activity were purified from media obtained from embryogenic Citrus sinensis L. Osbeck cv. Hamlin' callus suspension tissue cultures. ACHCM-1 had a Mr of 28,000 and a pI of 5.8 whereas ACHCM-2 was characterized by a Mr of 25,000 and a pI of 5. The N-terminal sequences of both proteins were similar and showed homology to class III phytochitinases.