Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex
Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex
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DOI：
10.1046/j.1365-313x.2003.01968.x
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发表时间：
2004-02-01
期刊：
影响因子：
7.2
通讯作者：
Kohno, K
中科院分区：
文献类型：
--
作者：
Konno, K;Hirayama, C;Kohno, K
许多植物含有当叶子受损时会渗出的乳胶，并且在其中发现了许多蛋白质和酶。这些乳胶蛋白和酶的作用目前还知之甚少。我们发现木瓜蛋白酶是木瓜树（Carica papaya，Caricaceae）乳胶中的一种半胱氨酸蛋白酶，是木瓜树防御鳞翅目幼虫的关键因素，例如寡食性蓖麻子（Saturniidae）和两种臭名昭著的多食性害虫，马梅斯特拉（Mamestra brasicae）（Noctuidae）和斜纹夜蛾（Spodoptera litura） （夜蛾科）。许多乳胶植物的叶子，包括木瓜和野生无花果榕（桑科），对鳞翅目幼虫表现出强烈的毒性和生长抑制作用，尽管这些物种没有明显的毒性因素的报道。当乳胶被洗掉后，这些乳汁植物的叶子就失去了毒性。木瓜和野生无花果的乳胶都富含半胱氨酸蛋白酶活性。 E-64是一种半胱氨酸蛋白酶特异性抑制剂，涂在木瓜和无花果叶表面后，完全消除了叶子的毒性。半胱氨酸蛋白酶，如木瓜蛋白酶、无花果蛋白酶和菠萝蛋白酶，都显示出毒性。结果表明，植物乳胶及其中的蛋白质，特别是半胱氨酸蛋白酶，为植物提供了针对草食性昆虫的一般防御机制。
Many plants contain latex that exudes when leaves are damaged, and a number of proteins and enzymes have been found in it. The roles of those latex proteins and enzymes are as yet poorly understood. We found that papain, a cysteine protease in latex of the Papaya tree (Carica papaya, Caricaceae), is a crucial factor in the defense of the papaya tree against lepidopteran larvae such as oligophagous Samia ricini (Saturniidae) and two notorious polyphagous pests, Mamestra brassicae (Noctuidae) and Spodoptera litura (Noctuidae). Leaves of a number of laticiferous plants, including papaya and a wild fig, Ficus virgata (Moraceae), showed strong toxicity and growth inhibition against lepidopteran larvae, though no apparent toxic factors from these species have been reported. When the latex was washed off, the leaves of these lactiferous plants lost toxicity. Latexes of both papaya and the wild fig were rich in cysteine-protease activity. E-64, a cysteine protease-specific inhibitor, completely deprived the leaves of toxicity when painted on the surface of papaya and fig leaves. Cysteine proteases, such as papain, ficin, and bromelain, all showed toxicity. The results suggest that plant latex and the proteins in it, cysteine proteases in particular, provide plants with a general defense mechanism against herbivorous insects.