Cloning and Characterization of a Balsam Pear Class I Chitinase Gene (Mcchit1) and Its Ectopic Expression Enhances Fungal Resistance in Transgenic Plants

Abstract

A balsam pear (Momordica charantia L.) chitinase (Mcchit1) was purified and sequenced at the N-terminal. The genomic and cDNA coding sequences of Mcchit1 were cloned by rapid amplification of 3′ cDNA ends (3′-RACE) and the Y-shaped adaptor dependent extension (YADE) method. Sequence analysis showed that the Mcchit1 protein is a class I chitinase containing a chitin-binding domain and a catalytic domain, but no C-terminal extension. Northern blot indicated that the Mcchit1 transcription is wound-inducible. Overexpression of Mcchit1 dramatically increased intercellular and intracellular endochitinase activities, suggesting that the Mcchit1 gene encodes a secretory endochitinase. It was also found that overexpression of Mcchit1 significantly enhanced resistance to the plant pathogenic fungus Phytophthora nicotianae in transgenic N. benthamiana plants and against Verticillium wilt in transgenic cottons, indicating that the Mcchit1 gene can be a useful gene in plant engineering against fungal diseases.