两种几丁质酶样蛋白在桑树乳胶中大量积累，表现出杀虫活性。

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

机构信息

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

出版信息

BMC Biochem. 2010 Jan 28;11:6. doi: 10.1186/1471-2091-11-6.

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.

背景

植物乳胶原液是一种高度特化细胞的细胞质，被认为在抵御草食性昆虫方面起着关键作用。因此，大量积累在乳胶原液中的蛋白质可能参与了防御系统。

结果

我们从桑树（Morus sp.）中纯化了乳胶原液丰富蛋白 a 和 b（LA-a 和 LA-b），并分析了它们的性质。LA-a 和 LA-b 的分子量分别约为 50 和 46 kDa，在乳胶原液的可溶性部分中含量丰富。Western blot 分析表明它们彼此之间具有序列相似性。通过 Edman 降解法确定的 LA-a 和 LA-b 的序列，在 N 端显示出植物几丁质酶的几丁质结合结构域。这些蛋白质表现出较小但显著的几丁质酶和壳聚糖酶活性。凝集素 RCA120 表明，与常见的植物几丁质酶不同，LA-a 和 LA-b 是糖基化的。当喂食模式昆虫黑腹果蝇（Drosophila melanogaster）的幼虫时，LA-a 和 LA-b 表现出杀虫活性。