生物谷报道:美国科研人员最近发现了两种与美洲王蝶的生物钟和迁徙有关的基因,其中一种基因是此前科研人员从未见过的。这一发现有助于专家深入了解王蝶的奇特本能。
生物钟是生物生命活动的周期性节律。这种节律与昼夜变化或四季变化等自然界的节律相一致。每年10月底,上亿只美洲王蝶从美国东北部和加拿大南部飞越数千公里来到温暖的墨西哥中部林区繁衍,尔后自然死亡。来年3月,这些王蝶的后代会飞回原来的栖息地。这一现象让生物学家感到费解。
马萨诸塞大学医学院教授史蒂文·里珀特等人在8日出版的美国《公共科学图书馆》杂志上发表了两篇论文说,他们此前在研究果蝇时发现,一种名为“CRY”的基因指导合成的“CRY”晶状体蛋白大约以24小时为周期不断地生成、降解,“CRY”蛋白的这种周期性节律对果蝇生理节律体系的影响至关重要。科研人员据此推测,美洲王蝶体内可能也有“CRY”蛋白,并发挥类似的作用。
然而进一步的研究显示,美洲王蝶体内不仅有“CRY”蛋白,还有另一种此前不为人知的晶状体蛋白和负责其合成的基因,该蛋白也是王蝶的“生理节律分子”,里珀特等人将其称为“CRY2”蛋白,负责合成这种蛋白的基因被称作“CRY2”基因。
里珀特指出,“CRY2”蛋白的结构更像脊椎动物的晶状体蛋白,“CRY2”蛋白的节律作用,可使美洲王蝶的生物钟节律和其根据太阳辨认迁徙方向的本能之间建立起神经联系。由此可见,上述两种蛋白的指导合成者——“CRY”基因和“CRY2”基因是王蝶开始迁徙和辨认方向所必需的基因。
目前,里珀特等研究人员已发现了这两种基因控制王蝶迁徙的过程,这一发现可能有助于专家找到不迁徙的一些美洲王蝶的脑部结构差异。(来源:新华网)
(《公共科学图书馆·综合》(PLoS ONE),doi:10.1371/journal.pone.0001345,Haisun Zhu, Steven M. Reppert)
(《公共科学图书馆·生物学》(PLoS Biology),doi:10.1371/journal.pbio.0060004,Haisun Zhu, Steven M. Reppert)
生物谷推荐英文原文:
Received: October 20, 2007; Accepted: November 23, 2007; Published: January 9, 2008
Chasing Migration Genes: A Brain Expressed Sequence Tag Resource for Summer and Migratory Monarch Butterflies (Danaus plexippus)
Haisun Zhu, Amy Casselman, Steven M. Reppert*
Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
Abstract
North American monarch butterflies (Danaus plexippus) undergo a spectacular fall migration. In contrast to summer butterflies, migrants are juvenile hormone (JH) deficient, which leads to reproductive diapause and increased longevity. Migrants also utilize time-compensated sun compass orientation to help them navigate to their overwintering grounds. Here, we describe a brain expressed sequence tag (EST) resource to identify genes involved in migratory behaviors. A brain EST library was constructed from summer and migrating butterflies. Of 9,484 unique sequences, 6068 had positive hits with the non-redundant protein database; the EST database likely represents ~52% of the gene-encoding potential of the monarch genome. The brain transcriptome was cataloged using Gene Ontology and compared to Drosophila. Monarch genes were well represented, including those implicated in behavior. Three genes involved in increased JH activity (allatotropin, juvenile hormone acid methyltransfersase, and takeout) were upregulated in summer butterflies, compared to migrants. The locomotion-relevant turtle gene was marginally upregulated in migrants, while the foraging and single-minded genes were not differentially regulated. Many of the genes important for the monarch circadian clock mechanism (involved in sun compass orientation) were in the EST resource, including the newly identified cryptochrome 2. The EST database also revealed a novel Na+/K+ ATPase allele predicted to be more resistant to the toxic effects of milkweed than that reported previously. Potential genetic markers were identified from 3,486 EST contigs and included 1599 double-hit single nucleotide polymorphisms (SNPs) and 98 microsatellite polymorphisms. These data provide a template of the brain transcriptome for the monarch butterfly. Our “snap-shot” analysis of the differential regulation of candidate genes between summer and migratory butterflies suggests that unbiased, comprehensive transcriptional profiling will inform the molecular basis of migration. The identified SNPs and microsatellite polymorphisms can be used as genetic markers to address questions of population and subspecies structure.