【bio-news】深入研究蜜蜂性基因

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http://www.ns.umich.edu/htdocs/releases/story.php?id=1017
Insights into honey bee sex gene could bring
sweet success in breeding
ANN ARBOR, Mich.—What makes a bee a he or a she?

Three years ago, scientists pinpointed a gene called csd that determines gender in honey bees, and now a research team led by Uniersity of Michigan eolutionary biologist Jianzhi "George" Zhang has unraeled details of how the gene eoled. The new insights could proe useful in designing strategies for breeding honey bees, which are major pollinators of economically important crops—and notoriously tricky to breed.

The findings of Zhang and collaborators appear in a special issue of Genome Research deoted to the biology of the honey bee. The issue will be published online and in print Oct. 26, coinciding with the publication of the honey bee genome sequence in the journal Nature.

Scientists hae long known that in bees—as well as wasps, ants, ticks, mites and some 20 percent of all animals—unfertilized eggs deelop into males, while females typically result from fertilized eggs. But that's not the whole story, and the discoery in 2003 of csd (the complementary sex determination gene) helped fill in the blanks. The gene has many ersions, or alleles. Males inherit a single copy of the gene; bees that inherit two copies, each a different ersion, become female. Bees that hae the misfortune of inheriting two identical copies of csd deelop into sterile males but are quickly eaten at the laral stage by female worker bees.

The system works fine in nature, where it preents the colony from wasting precious energy and resources on abnormal males incapable of carrying out the all-important role of mating. But in bees raised for honey or for pollinating crops, the sex-determination system can cause problems. Beekeepers inbreed bees to select desirable traits, but inbreeding raises the odds of producing fertilized eggs with two copies of the same csd allele. If too many sterile males result, the colony may die out.

"If we know more details about how many alleles there are and what their frequencies are, bee breeders can design better strategies to aoid producing sterile males," Zhang said. "Our work aids in this effort by proiding a direct tool to examine alleles from different populations."

In the research, Zhang and coworkers from U-M, Michigan State Uniersity and the Uniersity of Kansas sequenced csd genes from indiiduals in three closely related species of honey bee: the familiar backyard denizen Apis mellifera and the Asian honey bees Apis dorsata and Apis cerana. The group also sequenced six so-called neutral regions of the genome which, unlike genes, do not carry codes telling cells how to make proteins. Then, the researchers constructed gene genealogies—family trees for both the csd gene and the neutral regions.

Their results showed that csd is about seen times more ariable than neutral regions of the honey bee genome. In addition, many csd ariants are shared among the three species, eidence that the many different alleles hae been presered in these lineages for a ery long time.

Such a pattern supports the idea that an eolutionary mechanism known as balancing selection has been at work. Eolution works through the process of natural selection, in which genetic mutations that offer some adantage are faored, and those that hae harmful effects are weeded out. Typically, this results in one ersion of a gene becoming ery common and other ersions becoming rare or disappearing altogether. When balancing selection operates, howeer, natural selection faors a dierse mix of alleles, as seen with csd in honey bees.

The research also showed just how long the csd alleles hae been around.

"We estimated the age of the alleles at about 14 million years," said Zhang. "We don't know for sure when the species formed, but it's thought to be about six to eight million years ago, so the alleles are een older than the species."

Zhang collaborated on the research with postdoctoral fellow Soochin Cho and undergraduate student Daniel Green of the Uniersity of Michigan, Zachary Huang of Michigan State Uniersity and Deborah Smith of the Uniersity of Kansas. The researchers receied financial support from the U-M Office of the ice President for Research, the National Institutes of Health and the Uniersity of Kansas General Research Fund.

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Insights into honey bee sex gene could bring sweet success in breeding
性别基因的深入研究能使蜜蜂培育获得成功
Three years ago, scientists pinpointed a gene called csd that determines gender in honey bees, and now a research team led by Uniersity of Michigan eolutionary biologist has unraeled details of how the gene eoled. The new insights could proe useful in designing strategies for breeding honey bees, which are major pollinators of economically important crops—and notoriously tricky to breed.
三年前，科学家找到一个决定蜜蜂性别的称之为CDS的基因。现在以密西根州立大学发育生物学家Jianzhi "George" Zhang为首的研究小组阐明了该基因进化的具体细节。这项新的研究成果有益于设计蜜蜂培育方案。蜜蜂是重要经济作物的主要授粉者并且十分难以培育。
The findings of Zhang and collaborators appear in a special issue of Genome Research deoted to the biology of the honey bee. The issue will be published online and in print Oct. 26, coinciding with the publication of the honey bee genome sequence in the journal Nature.
张和同事的研究结果出现在致力于蜜蜂生物学研究的基因组研究的一个专题报告。该报告将在10月26日的电子版和印刷版《自然》杂志发表，一起发表的还有蜜蜂的基因组序列。
Scientists hae long known that in bees—as well as wasps, ants, ticks, mites and some 20 percent of all animals—unfertilized eggs deelop into males, while females typically result from fertilized eggs. But that's not the whole story, and the discoery in 2003 of csd (the complementary sex determination gene) helped fill in the blanks. The gene has many ersions, or alleles. Males inherit a single copy of the gene; bees that inherit two copies, each a different ersion, become female. Bees that hae the misfortune of inheriting two identical copies of csd deelop into sterile males but are quickly eaten at the laral stage by female worker bees.
长期以来科学家就认识到在蜜蜂种群里（还有黄蜂、蚂蚁、蜱、螨和约20%的动物），未受精卵发育成雄性，受精卵发育成雌性。但是该理论并不完整，2003年csd（增加的性别决定基因）填补了空白。该基因有很多等位基因。雄性继承了该基因的单拷贝，而继承了两个不同拷贝的蜜蜂发育成雌性。不幸继承了两个相同拷贝的蜜蜂发育成不育的雄性并且在幼虫时期被雌性工蜂吃掉。
The system works fine in nature, where it preents the colony from wasting precious energy and resources on abnormal males incapable of carrying out the all-important role of mating. But in bees raised for honey or for pollinating crops, the sex-determination system can cause problems. Beekeepers inbreed bees to select desirable traits, but inbreeding raises the odds of producing fertilized eggs with two copies of the same csd allele. If too many sterile males result, the colony may die out.
该机制在自然界运作良好，能够防止不正常的不能执行所有交配中的重要角色的雄蜂浪费宝贵的能量和资源。但是在培育成采蜜或者为作物授粉蜜蜂群体里，性别决定机制常常出问题。养蜂人通过蜜蜂杂交来选择所需要的性状，但是杂交也增加了产生两个相同拷贝的csd等位基因的机会。如果产生太多的不育蜂，该种群可能会灭绝。
"If we know more details about how many alleles there are and what their frequencies are, bee breeders can design better strategies to aoid producing sterile males," Zhang said. "Our work aids in this effort by proiding a direct tool to examine alleles from different populations."
“如果我们知道有关等位基因的数量和它们的序列的更多详细信息，育蜂者就可以采取更好的方法以避免产生不育的雄蜂，”张说，“我们通过提供从不同种群中检测等位基因的工具对该努力进行帮助。
In the research, Zhang and coworkers fromU-M, Michigan State Uniersity and the Uniersity of Kansas sequenced csd genes from indiiduals in three closely related species of honey bee: the familiar backyard denizen Apis mellifera and the Asian honey bees Apis dorsata and Apis cerana. The group also sequenced six so-called neutral regions of the genome which, unlike genes, do not carry codes telling cells how to make proteins. Then, the researchers constructed gene genealogies—family trees for both the csd gene and the neutral regions.
在该项研究中，张和来自U-M、密西根州和堪萨斯州立大学的同事对三个亲缘关系相近的蜜蜂品种中的个体进行csd基因的测序，该三个品种分别是喜爱后院居住的mellifera蜜蜂、亚洲蜜蜂dorsata和cerana.。
Their results showed that csd is about seen times more ariable than neutral regions of the honey bee genome. In addition, many csd ariants are shared among the three species, eidence that the many different alleles hae been presered in these lineages for a ery long time.
他们的研究结果表明csd基因比蜜蜂基因组其他的序列的变异性超过7倍。另外，在这三种蜜蜂中发现有许多的csd基因变异体，证明在这些品系中这许多的异等位基因长期被保留下来。
Such a pattern supports the idea that an eolutionary mechanism known as balancing selection has been at work. Eolution works through the process of natural selection, in which genetic mutations that offer some adantage are faored, and those that hae harmful effects are weeded out. Typically, this results in one ersion of a gene becoming ery common and other ersions becoming rare or disappearing altogether. When balancing selection operates, howeer, natural selection faors a dierse mix of alleles, as seen with csd in honey bees.
这种模式支持这样的观点：平衡选择的进化机制一直存在。进化通过自然选择的过程起作用，有益的基因突变被接受而有害的突变则被淘汰。通常这种选择导致一种基因的变异越来越普遍而其他的变异越来越少或者消失。当平衡选择起效的时候，自然选择偏向于产生多等位基因，就像蜜蜂群体中的csd等位基因。
The research also showed just how long the csd alleles hae been around.
该研究也说明了csd等位基因出现的时间。
"We estimated the age of the alleles at about 14 million years," said Zhang. "We don't know for sure when the species formed, but it's thought to be about six to eight million years ago, so the alleles are een older than the species."
张说：“我们估计该等位基因产生于1400万年前，我们不确定该品种的形成时间，但认为是600到800万年前，所以该等位基因比该品种出现的时间要早。”
Zhang collaborated on the research with postdoctoral fellow Soochin Cho and undergraduate student Daniel Green of the Uniersity of Michigan, Zachary Huang of Michigan State Uniersity and Deborah Smith of the Uniersity of Kansas. The researchers receied financial support from the U-M Office of the ice President for Research, the National Institutes of Health and the Uniersity of Kansas General Research Fund.
张和同事博士后Soochin Cho以及密西根大学的学生Daniel Green、密西根州力大学的Zachary Huang和堪萨斯州大学的Deborah Smith共同致力于该项研究。研究者得到U-M助理校长研究办公室、国立卫生研究院和堪萨斯州大学综合研究基金的资助。

编译
性别基因的深入研究能使蜜蜂培育获得成功

三年前，科学家找到一个决定蜜蜂性别的称之为CDS的基因。现在以密西根州立大学发育生物学家Jianzhi "George" Zhang为首的研究小组阐明了该基因进化的具体细节。这项新的研究成果有益于设计蜜蜂培育方案。蜜蜂是重要经济作物的主要授粉者并且十分难以培育。张和同事的研究结果出现在致力于蜜蜂生物学研究的基因组研究的一个专题报告。该报告将在10月26日的电子版和印刷版《自然》杂志发表，一起发表的还有蜜蜂的基因组序列。长期以来科学家就认识到在蜜蜂种群里（还有黄蜂、蚂蚁、蜱、螨和约20%的动物），未受精卵发育成雄性，受精卵发育成雌性。但是该理论并不完整，2003年csd（增加的性别决定基因）填补了空白。该基因有很多等位基因。雄性继承了该基因的单拷贝，而继承了两个不同拷贝的蜜蜂发育成雌性。不幸继承了两个相同拷贝的蜜蜂发育成不育的雄性并且在幼虫时期被雌性工蜂吃掉。该机制在自然界运作良好，能够防止不正常的不能执行所有交配中的重要角色的雄蜂浪费宝贵的能量和资源。但是在培育成采蜜或者为作物授粉蜜蜂群体里，性别决定机制常常出问题。养蜂人通过蜜蜂杂交来选择所需要的性状，但是杂交也增加了产生两个相同拷贝的csd等位基因的机会。如果产生太多的不育蜂，该种群可能会灭绝。“如果我们知道有关等位基因的数量和它们的序列的更多详细信息，育蜂者就可以采取更好的方法以避免产生不育的雄蜂，”张说，“我们通过提供从不同种群中检测等位基因的工具对该努力进行帮助。在该项研究中，张和来自U-M、密西根州和堪萨斯州立大学的同事对三个亲缘关系相近的蜜蜂品种中的个体进行csd基因的测序，该三个品种分别是喜爱后院居住的mellifera蜜蜂、亚洲蜜蜂dorsata和cerana.。他们的研究结果表明csd基因比蜜蜂基因组其他的序列的变异性超过7倍。另外，在这三种蜜蜂中发现有许多的csd基因变异体，证明在这些品系中这许多的异等位基因长期被保留下来。这种模式支持这样的观点：平衡选择的进化机制一直存在。进化通过自然选择的过程起作用，有益的基因突变被接受而有害的突变则被淘汰。通常这种选择导致一种基因的变异越来越普遍而其他的变异越来越少或者消失。当平衡选择起效的时候，自然选择偏向于产生多等位基因，就像蜜蜂群体中的csd等位基因。该研究也说明了csd等位基因出现的时间。张说：“我们估计该等位基因产生于1400万年前，我们不确定该品种的形成时间，但认为是600到800万年前，所以该等位基因比该品种出现的时间要早。”
张和同事博士后Soochin Cho以及密西根大学的学生Daniel Green、密西根州力大学的Zachary Huang和堪萨斯州大学的Deborah Smith共同致力于该项研究。研究者得到U-M助理校长研究办公室、国立卫生研究院和堪萨斯州大学综合研究基金的资助。

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