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Open Access Highly Accessed Research article

Two chitinase-like proteins abundantly accumulated in latex of mulberry show insecticidal activity

Sakihito Kitajima*, Kaeko Kamei, Shigeru Taketani, Masamitsu Yamaguchi, Fumiko Kawai, Aino Komatsu and Yoshihiro Inukai

Author Affiliations

Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki Sakyo-ku, Kyoto 606-8585, Japan

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BMC Biochemistry 2010, 11:6  doi:10.1186/1471-2091-11-6

Published: 28 January 2010

Abstract

Background

Plant latex is the cytoplasm of highly specialized cells known as laticifers, and is thought to have a critical role in defense against herbivorous insects. Proteins abundantly accumulated in latex might therefore be involved in the defense system.

Results

We purified latex abundant protein a and b (LA-a and LA-b) from mulberry (Morus sp.) and analyzed their properties. LA-a and LA-b have molecular masses of approximately 50 and 46 kDa, respectively, and are abundant in the soluble fraction of latex. Western blotting analysis suggested that they share sequence similarity with each other. The sequences of LA-a and LA-b, as determined by Edman degradation, showed chitin-binding domains of plant chitinases at the N termini. These proteins showed small but significant chitinase and chitosanase activities. Lectin RCA120 indicated that, unlike common plant chitinases, LA-a and LA-b are glycosylated. LA-a and LA-b showed insecticidal activities when fed to larvae of the model insect Drosophila melanogaster.

Conclusions

Our results suggest that the two LA proteins have a crucial role in defense against herbivorous insects, possibly by hydrolyzing their chitin.