草莓的秘密性生活
Woman and man, hen and rooster, cow and bull—separate sexes may seem fundamental to nature, but they’re an oddity for most plants.
男人和女人，母鸡和公鸡，母牛和公牛——分离的两性在自然界是很常见的，不过对大多数植物来说这还是件稀奇事。
Now, scientists have figured out how strawberries, which have the youngest known sex chromosomes of any plant or animal, made their recent transition to male and female.
如今，科学家们已经发现了草莓是怎样最初区分出雄性和雌性的，草莓在已知所有的植物和动物中拥有最新才破解的性染色体。
The unusual “jumping” genes responsible could mean sex differences can change faster in plants than anyone realized.
这种不同寻常的“跳跃”基因可能意味着，在植物中，性别差异的变化比任何人意识到的都要快。
晚上吃水果好不好
“For the first time, we now have a view of sex chromosome evolution over space and time,” says Alex Harkess, an evolutionary biologist at Donald Danforth Plant Science Center in St. Louis, Missouri, who was not involved in the study.
“现在这是首次，让我们认识到性染色体是如何是在时间和空间上进化的，”艾利克斯.哈吉斯说道，他是密苏里州圣路易市的唐纳德.丹佛斯植物科学中心的一名进化生物学家，并未参与此次研究。
“It’s not just about the establishment of sex chromosomes, it’s how the sex-determining regions continue to evolve.”
“这不仅仅是关于性染色是如何建立的，而且涉及性别决定区域是如何后续进化的。”
Animals have ancient sex chromosomes with a common origin.
动物们的染色体非常古老而且拥有共同的起源。
But in plants, sex chromosomes have arisen only recently (in the last few million years), and most plants are generally hermaphrodites—which contain both male and female sex organs.
不过在植物当中，性染色出现较晚（最近几百万年时间才出现），而且大部分植物的一般都是两性体—既有雌性又有雄性器官。
Only about 6% have split into different sexes, including garden asparagus, papaya, hops, and marijuana.
只有6%是两性分离的，包括芦笋，木瓜，啤酒花和烟草等。
Strawberries, as one uneducated Ohio farmer discovered in the 1840s, come in three flavors: male, female, and combo.
而草莓，是1840年代俄亥俄州一名没文化的农民发现的，它有三种性别：雄性，雌性和双性。
To find out how those flavors evolved, ecologist Tia-Lynn Ashman at the University of Pittsburgh in Pennsylvania has spent nearly 20 years showing that different locations on the strawberry genome can control sex.
为了找出这些性别是如何进化的，宾夕法尼亚州的匹兹堡大学的生态学家蒂亚-琳.阿希曼花了将近20年的时间来证实草莓基因组的不同区块都可以控制性别。
But figuring out where those genes were located was like finding a treasure in a hall of mirrors: Unlike humans, which have just two copies of each of our 23 chromosomes, strawberries have a whopping eight copies of seven chromosomes, for a grand total of 56.
不过要找到这些基因位于何处就好比在一个装满镜子的大厅里寻宝一样：跟人类不同，人类有23对染色体，而草莓则拥有7个染色体的八倍复制体，总共是56个染色体。
Ashman’s first stroke of luck came when she and her team found the first evidence of male- and female-determining regions in an East Coast variety of a common North American wild strawberry (Fragaria virginiana) some 10 years ago.
阿希曼的第一次幸运发现是在大约十年前，她和她的团队在普通的北美野生草莓一种东海岸品种(Fragaria virginiana)中找到了雄性和雌性决定区域的时候。
But when they found the same sex region in a closely related Oregon beach wild strawberry, F. chiloensis, it was in an entirely different place on an entirely different chromosome.
不过他们在一种亲缘关系很近的俄勒冈海岸野生草莓 F. chiloensis中发现同一的性别区域，则是在全然不同的染色体的完全不同的位点。
The same was true of a third variety of strawberry.
在第三个草莓品种中也有同样的发现。
What were these regions doing in different places?
为什么这些区域会在不同的位点出现呢？
Ashman says the obvious answer was that the strawberries had developed different sexes independently.
阿希曼说答案明显是因为不同草莓品种各自进化出了不同的性别。
But another, less probable, explanation was that a region of DNA had arisen once and was moving around the genome.
不过另一种，概率更小的解释是某个DNA的区域曾出现过，然后在基因组中进行了移动。
When the first strawberry genome project came to fruition in 2011, allowing for more detailed genetic studies, evolutionary biologist Aaron Liston of Oregon State University in Corvallis and evolutionary geneticist Jacob Tennessen, now at the Harvard T.H. Chan School of Public Health in Boston, teamed up with Ashman to take a closer look.
当2011年首个草莓金银组项目取得成果后，为进一步研究带来了条件，科瓦利斯市的俄勒冈州立大学的进化生物学家艾伦.里斯顿还有如今在波士顿市的哈佛的陈振聪公共卫生学院的进化遗传学家雅各布.滕乐森跟阿希曼一起组队来进行研究。
In a brute force approach, they sequenced 60 F. virginiana and F. chiloensis plants, evenly divided between males and females, to see whether any DNA was unique to the females.
用蛮力的方法，他们对六十株F. virginiana和 F. chiloensis 品种的草莓，雌雄各半，进行了基因测序，以此来探究是否有DNA是雌性特有的。
They asked what genetic sequence was present in all females, but absent in all males.
他们想问是否有某些基因序列在所有雌性中出现，而在雄性中缺失。
Sure enough, all females shared a short sequence that had jumped at least twice as the plants reproduced over many generations, the researchers reported late last month in PLOS Biology.
研究人员在上个月末的《公共科学图书馆·生物学》(PLOS Biology)杂志上报道说，果然，所有的雌性都有一个短序列，这个序列在多代繁殖中至少跳跃了两次。
What’s more, with each jump, the number of female-specific genes on the sequence increased.
另外，每跳跃一次，序列中的雌性特有基因的数目就会增加一次。
Those traveling “souvenirs” increased the difference between the sex chromosomes, the researchers speculate.
研究员们估计，这些旅行的“纪念品基因”增加了性染色体之间的不同。
In humans and other animals, such sex-specific differences eventually became extreme.
在人类和其他动物中，这种性别特定的区别最后变得极端化。
In strawberries, the short jumping sequence contained two genes with potential roles in pollen and fruit development.
在草莓中，这种短的跳跃的序列包含了可能在花粉和果实发育中相关的两个基因。
“This study provides the first observations suggesting that a sex determining region in a plant can 'jump’ from an initial location to a new one,” wrote The University of Edinburgh evolutionary biologist Deborah Charlesworth—a pioneer in the evolution of sex chromosomes—in an email.
“这项研究提供的一手观察表明一种植物中的性别决定区域是可以从最初的位点跳跃到新位点的，”爱丁堡大学的进化生物学家黛博拉.查尔斯沃斯—性染色体进化研究的先锋学者—在邮件中写道。
“The study does a heroic job of trying to sort this out.”
“这些研究在理清这个问题方面做出了杰出贡献。”
The researchers caution that the functions of the two genes and details of how they “jump” still need to be confirmed.
研究员们提醒道这两个基因的功能以及它们具体是如何“跳跃”的仍有待证实。
And Ashman says the findings set the stage for an even bigger question: Why do these regions bother jumping in the first place?
而阿希曼说这项发现又引出了另一个更大的问题：这些区域最初为什么会跳跃呢 ？
Ashman and Liston will be following up.
阿希曼和里斯顿会进行后续的研究。
But don’t look for the special male and female strawberries at your grocery stores or farmers’ markets any time soon.
不过先别急着在杂货店或者农场集市中寻找特别的雄性或者雌性的草莓。
In a final plot twist, the hybrid descendants of the wild strawberries in the study have all had the sex differences bred out of them.
在最后一个情节转折中，研究中野生草莓的杂交后代都继承了从它们身上培育出的性别差异。
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