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ARS Home » Research » Publications at this Location » Publication #62120
Title: CDNA CLONING AND EXPRESSION OF A CLASS II ACIDIC CHITINASE FROM SWEET ORANGE

Author
item NAIRN, C - UNIV. OF FLORIDA
item Niedz, Randall
item Hearn, C
item Yelenosky, George
item Mayer, Richard

Submitted to: Plant and Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: A gene was isolated from the Valencia orange that codes for an enzyme called chitinase. Certain chitinases can inhibit the growth of some fungi, including fungi that cause disease problems in plants. We obtained the nucleic acid sequence of this particular chitinase gene and showed that it is found in Valencia cell cultures as well as young bark of 2 year old Valencia trees. It also appears to have structural characteristics different from other reported plant chitinases. The purpose of this research is to identify the particular chitinase genes involved in making citrus trees more resistant to fungal diseases and insect feeding.

Technical Abstract: A novel citrus cDNA clone (pCSC 01) was isolated from a cDNA library prepared from a nonembryogenic cell line of Citrus sinensis cv 'Valencia' (Val88 1) using a tobacco cDNA clone encoding a basic chitinase (PROB3). The pCSC 01 insert contained an 876 bp open reading frame encoding a 292 amino acid polypeptide. The predicted polypeptide amino sequence is a class II chitinase because it shares >50% sequence similarity with tobacco class I chitinase but lacks an N terminal cysteine rich domain. A 44 amino acid region of the pCSC 01 polypeptide N terminal region matches the N terminal sequence of A4 AN1, a previously isolated chitinase from Val88 1. Expression studies in leaves, roots, flavedo, and young bark of 'Valencia' indicated that only mRNAs from young, green bark hybridized to the pCSC 01 probe. Although the pCSC 01 sequence is expressed in the nonembryogenic cell line Val88 1, it is not detected in a 'Valencia' embryogenic cell line (Val88 1E), even when the cells are treated with methyl jasmonate, chitosan, or yeast extract, known elicitors of chitinase in some other plant species.