不同虫态烟粉虱诱导植物防御反应差异性研究

The mechanism of plant defense to phloem feeding insects such as aphids and whiteflies is largely unknown. Previous studies show that phloem feeding insect often induce different plant defense, however, little is known whether infestation by different developmental stages of the same species would induce similar defense response or not. Previous studies showed that performance of solid feeding nymphs and free feeding adults of an invasive whitefly, Bemisia tabaci, were significantly different on tobacco plants, indicating that plants may activate different defense upon their infestation. Here we use whitefly and tobacco plants as model system, using Digital Gene Expression (DGE) which based on next-generation high throughout sequencing technology to compare defense-related gene expression profiles of plants infested by nymphs and adults, to reveal the reason why nymphs and adults perform differently on the same host plant. Furthermore, it has been shown that infestation of whitefly nymphs activate SA pathway but suppress JA pathway, which resulted in better performance of nymphs on the host plants although it is not clear whether adults also benefit from it or not. We will study the effect of nymph infestation on the performance of adults on host plant to verify whether such intraspecies mutualism relationship exist or not and its role in the invasion process of this whitefly.

植物对以蚜虫、粉虱为代表的韧皮部取食昆虫的防御机制还不清楚。不同韧皮部取食昆虫诱导的植物防御反应往往存在较大差异，目前还不清楚同种昆虫不同发育阶段侵染诱导的植物防御反应是否相同。研究发现固定取食的烟粉虱若虫和自由取食成虫在烟草上的适合性明显不同，暗示植物对成、若虫的防御反应可能存在较大差异。本项目试图以烟粉虱-烟草为研究对象，应用基于下一代高通量测序技术的数字化基因表达（Digital Gene Expression, DGE）技术比较烟粉虱若虫和成虫侵染植物防御相关基因表达差异，从分子层面解释烟草对烟粉虱成虫和若虫适合度存在差异的现象。此外，有研究表明烟粉虱若虫侵染可导致植物SA途径上调和JA途径下调，从而导致其在植物上的适合性提高，目前还不清楚这种调控作用是否会对成虫产生有利影响。本项目拟通过研究烟粉虱若虫侵染对成虫适合度的影响来探讨是否存在种内互惠关系及其在生物入侵中所起作用。

烟粉虱是全球范围内危害最为严重的入侵生物之一。尽管人们对其开展了大量研究，但目前仍未完全清楚其入侵机制。本研究发现烟粉虱成虫在不适合寄主植物烟草上（品种为NC89）上的寿命和产卵量均很低，而若虫在该植物上的发育历期和存活率却很高，表明若虫和成虫在烟草上的适合性明显不同，暗示植物对成、若虫的防御反应可能存在较大差异。进一步研究发现，烟粉虱成虫在若虫取食后烟草上的寿命和产卵量分别是其在对照烟草上的3.7倍和6.4倍，表明烟粉虱若虫取食显著提高了烟粉虱成虫对烟草的适合度，即烟粉虱若虫和成虫在不适合寄主植物烟草上存在“种内互惠共生”现象。烟粉虱若虫对不适合寄主植物的改造能力很可能是烟粉虱具有极广的寄主范围的重要原因，也是烟粉虱在全球范围内广泛入侵的重要机制。为揭示“种内互惠共生”现象的生理机制，我们应用基于下一代高通量测序技术的数字化基因表达（Digital Gene Expression, DGE）技术分析了烟粉虱若虫侵染导致的烟草基因表达谱变化，共鉴定出上调基因1149个，下调基因1072个，进一步分析发现差异表达基因多为植物抗逆、抗病相关基因而非抗虫相关基因，表明烟粉虱若虫侵染诱导的植物防御反应与病原菌和逆境胁迫类似。烟粉虱若虫侵染有效避免了植物抗虫相关防御基因的启动，推测这可能是其在不适合寄主上顺利发育和存活的内在机制。总之，本研究首次发现 “种内互惠共生”这一重要生态学现象并从分子层面初步揭示了该现象的内在机制，为揭示烟粉虱生物入侵机制提供了新的思路。