Department of Life Sciences, Tunghai University, Taichung, Taiwan.
J Exp Biol. 2010 Nov 15;213(Pt 22):3906-10. doi: 10.1242/jeb.046730.
The chemical and mechanical properties of spider major ampullate (MA) silks vary in response to different prey, mostly via differential expression of two genes - MaSp1 and MaSp2 - although the spinning process exerts additional influence over the mechanical properties of silk. The prey cues that initiate differential gene expression are unknown. Prey nutrients, vibratory stimuli and handling have been suggested to be influential. We performed experiments to decouple the vibratory stimuli and handling associated with high and low kinetic energy prey (crickets vs flies) from their prey nutrients to test the relative influence of each as inducers of silk protein expression in the orb web spider Nephila pilipes. We found that the MA silks from spiders feeding on live crickets had greater percentages of glutamine, serine, alanine and glycine than those from spiders feeding on live flies. Proline composition of the silks was unaffected by feeding treatment. Increases in alanine and glycine in the MA silks of the live-cricket-feeding spiders indicate a probable increase in MaSp1 gene expression. The amino acid compositions of N. pilipes feeding on crickets with fly stimuli and N. pilipes feeding on flies with cricket stimuli did not differ from each other or from pre-treatment responses, so these feeding treatments did not induce differential MaSp expression. Our results indicate that cricket vibratory stimuli and handling interact with nutrients to induce N. pilipes to adjust their gene expression to produce webs with mechanical properties appropriate for the retention of this prey. This shows that spiders can genetically alter their silk chemical compositions and, presumably, mechanical properties upon exposure to different prey types. The lack of any change in proline composition with feeding treatment in N. pilipes suggests that the MaSp model determined for Nephila clavipes is not universally applicable to all Nephila.
蜘蛛主要壶腹（MA）丝的化学和机械性能会因不同的猎物而变化，主要是通过两种基因 - MaSp1 和 MaSp2 - 的差异表达来实现，尽管纺丝过程对丝的机械性能有额外的影响。触发差异基因表达的猎物线索尚不清楚。有人认为猎物的营养物质、振动刺激和处理对其有影响。我们进行了实验，将与高、低动能猎物（蟋蟀与苍蝇）相关的振动刺激和处理与其猎物的营养物质分离开来，以测试它们作为蜘蛛 Nephila pilipes 网丝蛋白表达诱导物的相对影响。我们发现，以活蟋蟀为食的蜘蛛的 MA 丝中，谷氨酰胺、丝氨酸、丙氨酸和甘氨酸的百分比高于以活苍蝇为食的蜘蛛。丝中脯氨酸的组成不受饲养处理的影响。活蟋蟀喂养的 MA 丝中丙氨酸和甘氨酸的增加表明 MaSp1 基因表达可能增加。用苍蝇刺激喂养蟋蟀和用蟋蟀刺激喂养苍蝇的 N. pilipes 的 MA 丝的氨基酸组成彼此之间以及与预处理反应没有差异，因此这些饲养处理没有诱导差异的 MaSp 表达。我们的结果表明，蟋蟀的振动刺激和处理与营养物质相互作用，促使 N. pilipes 调整其基因表达，以产生适合保留这种猎物的具有机械性能的网。这表明蜘蛛可以在暴露于不同的猎物类型时，通过遗传改变其丝的化学成分，大概还有机械性能。N. pilipes 中喂食处理对脯氨酸组成没有任何变化，这表明针对 Nephila clavipes 确定的 MaSp 模型并不普遍适用于所有 Nephila。
