海藻糖代谢及其调控昆虫几丁质合成研究进展
摘要：摘要：海藻糖为一种非还原性糖，广泛存在于细菌、藻类、真菌、植物和无脊椎动物中。海藻糖被称为昆虫“血糖”，源于该糖为昆虫血淋巴中的主要糖类物质，在昆虫生长、发育、蜕皮等正常生理活动中有着重要的作用。昆虫的海藻糖先由海藻糖合成酶（trehalose-6-phosphate synthase，TPS）生成海藻糖-6-磷酸，然后通过海藻糖磷酸脂酶（trehalose-6-phosphate phosphatase，TPP）最终合成海藻糖，在能量需求时通过海藻糖酶（trehalase，TRE）降解为葡萄糖，用于能量供给。几丁质为昆虫表皮、中肠围食膜和气管系统的主要组成成分，昆虫在发育过程中需要蜕掉旧表皮，形成新的表皮，该过程一直是害虫控制的重要靶标途径。海藻糖酶为昆虫几丁质合成途径的第一个酶，在几丁质合成通路中有着重要的功能。那么海藻糖代谢又是如何调控几丁质合成途径来控制昆虫的蜕皮及几丁质代谢的呢？随着国内外海藻糖代谢相关基因功能研究的深入开展，研究结果表明昆虫海藻糖供给在几丁质合成中具有重要的作用，海藻糖酶分为可溶性和膜结合型两类，可溶性TRE和TPS在不同昆虫种类中具有多个同源基因，表明昆虫海藻糖代谢进化途径多样化。其次，海藻糖代谢直接调控几丁质合成途径，不论是海藻糖合成酶还是海藻糖酶基因的低表达，均能控制海藻糖使其供给不平衡，从而导致几丁质合成途径受阻，特别是几丁质合成酶基因表达降低而造成几丁质含量下降，该调控作用可进一步引起昆虫蜕皮困难、翅发育畸形等，甚至是大量死亡。再次，海藻糖酶抑制剂能够抑制可溶性和膜结合型两类海藻糖酶活性、引起几丁质合成通路相关基因及几丁质酶基因表达的显著下降，导致几丁质含量显著降低，产生高比例的昆虫个体死亡。这些结果充分表明，一旦昆虫海藻糖代谢的供给平衡被打破，会直接影响到昆虫的几丁质合成乃至昆虫的蜕皮与发育过程。本文综述前人在海藻糖代谢调控几丁质合成方面的最新研究成果，为将来开发和利用海藻糖酶抑制剂及海藻糖合成酶抑制剂等绿色农药防治害虫提供理论依据。
关键词：海藻糖代谢；海藻糖合成酶；海藻糖酶；几丁质合成；RNA干扰
Advances in Trehalose Metabolism and its Regulation of insect chitin Synthesis
Abstract: Trehalose as a non-reducing disaccharide is widely found in bacteria, algae, fungi, plants, and invertebrates. Moreover, trehalose is regarded as lsquo;blood sugarrsquo;, since it is the primary carbohydrate substances in insects, which plays a key role in normal physiological processes, such as growth, development, moulting and so on. The trehalose in insects is synthesized by trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphatase (TPP). Trehalase (TRE) can hydrolyze trehalose into glucose rapidly and provide energy when energy is needed. Chitin is the main component of insect epidermis, midgut peritrophic membrane and tracheal system. During developmental stages, insects need to shed old epidermis for forming new epidermis. This process has always been an important target for pest control. TRE is the first enzyme in the chitin biosynthesis pathway, which has significant functions of influencing the chitin metabolism by regulating chitin synthesis pathway. So how does trehalose metabolism regulate chitin synthesis pathways to control insect molt and chitin metabolism? With further research on the function of trehalose metabolism related genes over the world, these results showed that the providing of trehalose in insects plays a pivotal role in chitin synthesis. In addition, trehalase can be divided into soluble and membrane-bound types. The soluble TRE and TPS have multiple homologous genes in different insect species, indicating that the trehalose metabolic evolution of insects is diversified. Second, trehalose metabolism can regulate the chitin synthesis directly. Whether the low expression of TPS or TRE can break the supply balance of trehalose, resulting in chitin synthesis pathway blocked, especially the expression of chitin synthase gene decreased which lead to low chitin content, and further cause molting difficulties, developmental deformities, even death. Furthermore, trehalase inhibitors can inhibite the activities between soluble and membrane-bound TRE, resulting in a significant decrease in chitin synthesis pathway-related genes and chitinase gene expression, low chitin content and high proportion of death. These results indicate that once the supply balance of insect trehalose metabolism is broken, it will directly affect the chitin synthesis of insects which related to the process of molting and development. In this report, the research progress on trehalose metabolism and the regulation of chitin biosynthesis are introduced and summarized, in the desire to provide a theoretical basis for the development of green pesticides represented by trehalase inhibitor and trehalose-6-phosphate synthase pathway inhibitor aimed at pest control.
Key words: trehalose metabolism; trehalose-6-phosphate synthase (TPS); trehalase; chitin biosynthesis; RNA interference
海藻糖为一种非还原性糖，广泛存在于细菌、真菌、植物和无脊椎动物中，海藻糖不仅是昆虫血淋巴中的重要糖类和能量物质，而且在昆虫的生长、发育、蜕皮变态等一系列生命活动活动中具有重要作用，因此被称为昆虫的“血糖”[1-3]。昆虫通过海藻糖合成酶及海藻糖酶来合成和降解海藻糖，为其进行的一系列生命活动提供能源。海藻糖不仅是能量来源物质，而且是一种重要的抗逆物质，在各种环境压力条件下保护机体免受损伤[4-7]。昆虫的外骨骼主要由几丁质构成，其幼虫每生长到一定的阶段都需要蜕掉旧的表皮，形成新的表皮，这个过程由几丁质合成通路及几丁质降解途径来共同完成[8]。海藻糖酶是昆虫几丁质合成通路的第一个酶，研究表明海藻糖的合成和降解都能通过控制几丁质合成通路从而影响昆虫发育[9-11]。而海藻糖合成酶为海藻糖合成的限速酶，同时考虑到包括人类在内的高等哺乳动物不能自身合成海藻糖[12]，海藻糖合成途径具有作为相对安全的控制靶标的潜力[13]。然而，昆虫海藻糖代谢能否且又是如何调控几丁质合成途径的？通过昆虫海藻糖代谢相关基因的功能研究，越来越多的研究结果表明当海藻糖供给平衡被打破会导致昆虫几丁质合成受阻，通路相关基因的表达显著降低、几丁质含量显著下降并产生高死亡率[9,14-16]，这表明海藻糖代谢途径适合作为害虫的控制靶标[17-18]。
昆虫几丁质合成与海藻糖代谢
1.1 昆虫几丁质
