Two chitinase-like proteins abundantly accumulated in latex of mulberry show insecticidal activity.
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.
Kitajima
Sakihito
S
Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan. sakito@kit.ac.jp
Kamei
Kaeko
K
Taketani
Shigeru
S
Yamaguchi
Masamitsu
M
Kawai
Fumiko
F
Komatsu
Aino
A
Inukai
Yoshihiro
Y
D000595:Amino Acid Sequence; D000818:Animals; D004331:Drosophila melanogaster / Q000187:drug effects; D006031:Glycosylation; D007306:Insecticides / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D007840:Latex / Q000378:metabolism*; D008969:Molecular Sequence Data; D031625:Morus / Q000378:metabolism*; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*
D007306:Insecticides; D007840:Latex; D010940:Plant Proteins