生物谷報道：美國科研人員最近發(fā)現了兩種與美洲王蝶的生物鐘和遷徙有關的基因,，其中一種基因是此前科研人員從未見過的。這一發(fā)現有助于專家深入了解王蝶的奇特本能,。
生物鐘是生物生命活動的周期性節(jié)律,。這種節(jié)律與晝夜變化或四季變化等自然界的節(jié)律相一致。每年10月底,，上億只美洲王蝶從美國東北部和加拿大南部飛越數千公里來到溫暖的墨西哥中部林區(qū)繁衍,，爾后自然死亡。來年3月,，這些王蝶的后代會飛回原來的棲息地,。這一現象讓生物學家感到費解。
馬薩諸塞大學醫(yī)學院教授史蒂文·里珀特等人在8日出版的美國《公共科學圖書館》雜志上發(fā)表了兩篇論文說,，他們此前在研究果蠅時發(fā)現,，一種名為“CRY”的基因指導合成的“CRY”晶狀體蛋白大約以24小時為周期不斷地生成、降解,，“CRY”蛋白的這種周期性節(jié)律對果蠅生理節(jié)律體系的影響至關重要,。科研人員據此推測,，美洲王蝶體內可能也有“CRY”蛋白,，并發(fā)揮類似的作用。
然而進一步的研究顯示,，美洲王蝶體內不僅有“CRY”蛋白,，還有另一種此前不為人知的晶狀體蛋白和負責其合成的基因，該蛋白也是王蝶的“生理節(jié)律分子”,，里珀特等人將其稱為“CRY2”蛋白,，負責合成這種蛋白的基因被稱作“CRY2”基因。
里珀特指出,，“CRY2”蛋白的結構更像脊椎動物的晶狀體蛋白,，“CRY2”蛋白的節(jié)律作用，可使美洲王蝶的生物鐘節(jié)律和其根據太陽辨認遷徙方向的本能之間建立起神經聯(lián)系,。由此可見,，上述兩種蛋白的指導合成者——“CRY”基因和“CRY2”基因是王蝶開始遷徙和辨認方向所必需的基因。
目前,，里珀特等研究人員已發(fā)現了這兩種基因控制王蝶遷徙的過程,，這一發(fā)現可能有助于專家找到不遷徙的一些美洲王蝶的腦部結構差異,。（來源：新華網）
（《公共科學圖書館·綜合》（PLoS ONE），doi:10.1371/journal.pone.0001345,，Haisun Zhu, Steven M. Reppert）
（《公共科學圖書館·生物學》（PLoS Biology）,，doi:10.1371/journal.pbio.0060004，Haisun Zhu, Steven M. Reppert）
生物谷推薦英文原文：
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.
