Plant Biochemistry Laboratory, Department of Plant Biology and Biotechnology, University of Copenhagen, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark.
BMC Genomics. 2009 Dec 2;10:574. doi: 10.1186/1471-2164-10-574.
An essential driving component in the co-evolution of plants and insects is the ability to produce and handle bioactive compounds. Plants produce bioactive natural products for defense, but some insects detoxify and/or sequester the compounds, opening up for new niches with fewer competitors. To study the molecular mechanism behind the co-adaption in plant-insect interactions, we have investigated the interactions between Lotus corniculatus and Zygaena filipendulae. They both contain cyanogenic glucosides which liberate toxic hydrogen cyanide upon breakdown. Moths belonging to the Zygaena family are the only insects known, able to carry out both de novo biosynthesis and sequestration of the same cyanogenic glucosides as those from their feed plants. The biosynthetic pathway for cyanogenic glucoside biosynthesis in Z. filipendulae proceeds using the same intermediates as in the well known pathway from plants, but none of the enzymes responsible have been identified. A genomics strategy founded on 454 pyrosequencing of the Z. filipendulae transcriptome was undertaken to identify some of these enzymes in Z. filipendulae.
Comparisons of the Z. filipendulae transcriptome with the sequenced genomes of Bombyx mori, Drosophila melanogaster, Tribolium castaneum, Apis mellifera and Anopheles gambiae indicate a high coverage of the Z. filipendulae transcriptome. 11% of the Z. filipendulae transcriptome sequences were assigned to Gene Ontology categories. Candidate genes for enzymes functioning in the biosynthesis of cyanogenic glucosides (cytochrome P450 and family 1 glycosyltransferases) were identified based on sequence length, number of copies and presence/absence of close homologs in D. melanogaster, B. mori and the cyanogenic butterfly Heliconius. Examination of biased codon usage, GC content and selection on gene candidates support the notion of cyanogenesis as an "old" trait within Ditrysia, as well as its origins being convergent between plants and insects.
Pyrosequencing is an attractive approach to gain access to genes in the biosynthesis of bio-active natural products from insects and other organisms, for which the genome sequence is not known. Based on analysis of the Z. filipendulae transcriptome, promising gene candidates for biosynthesis of cyanogenic glucosides was identified, and the suitability of Z. filipendulae as a model system for cyanogenesis in insects is evident.
植物和昆虫共同进化的一个重要驱动因素是产生和处理生物活性化合物的能力。植物产生生物活性天然产物以进行防御，但有些昆虫会解毒和/或隔离这些化合物，从而为竞争较少的新生态位开辟了道路。为了研究植物-昆虫相互作用中共同适应的分子机制，我们研究了 Lotus corniculatus 和 Zygaena filipendulae 之间的相互作用。它们都含有氰苷葡萄糖苷，在分解时会释放出有毒的氰化氢。属于 Zygaena 科的飞蛾是已知的唯一能够从头合成和隔离与它们的饲料植物相同的氰苷葡萄糖苷的昆虫。在 Z. filipendulae 中，氰苷葡萄糖苷生物合成的生物合成途径使用与植物中著名途径相同的中间体，但尚未鉴定出负责这些途径的任何酶。我们采用基于 454 焦磷酸测序的 Z. filipendulae 转录组学策略，旨在鉴定 Z. filipendulae 中的一些酶。
将 Z. filipendulae 转录组与已测序的 Bombyx mori、Drosophila melanogaster、Tribolium castaneum、Apis mellifera 和 Anopheles gambiae 基因组进行比较，表明 Z. filipendulae 转录组的覆盖率很高。Z. filipendulae 转录组序列的 11%被分配到基因本体论类别。基于序列长度、拷贝数以及在 D. melanogaster、B. mori 和氰化蝴蝶 Heliconius 中紧密同源物的存在/不存在，鉴定出参与氰苷葡萄糖苷生物合成的酶（细胞色素 P450 和家族 1 糖基转移酶）的候选基因。对偏倚密码子使用、GC 含量和基因候选物的选择的检查支持这样一种观点，即氰化作用是 Ditrysia 中的一个“古老”特征，并且它的起源在植物和昆虫之间是趋同的。
焦磷酸测序是一种很有吸引力的方法，可以获得未知基因组的昆虫和其他生物体中生物活性天然产物生物合成的基因。基于 Z. filipendulae 转录组的分析，鉴定出氰苷葡萄糖苷生物合成的有前途的候选基因，并且 Z. filipendulae 作为昆虫氰化作用的模型系统是可行的。
