Nature杂志要览
antigen
Nature 457: 7228
22 January 2009
===================================
[自然要览]
（选自英国Nature杂志，2009年1月22日出版）
封面故事：南极大陆的变暖速度
Warming of the Antarctic ice-sheet surface since the 1957
International
Geophysical Year
南极半岛是地球上变暖最快的地方之一，但一直难以确定整个南极大陆范围内的变化是
否与全球平均气温明显上升的趋势相似。这是因为来自冰层气象站的连续记录大多数都
是关于沿海地区的，它们所提供的关于大陆内部的信息非常少。在根据卫星数据（在短
期内有很好的空间覆盖）和来自气象站的气温数据（长时间尺度）（研究人员通过一个
用来估计缺失气候数据点的算法将这两个方面的数据融合了起来）对1957–2006年间南
极表面温度趋势所做的一项新的重建工作中，这个问题被绕开了。最后得到的记录（比
以前填补空白的数据更可靠）表明，总体上南极大陆在以大约每10年0.1 °C的速度变
暖，冬季和春季及在西南极变暖更强一些。本期封面所示为变暖的地理范围，其中“热
点”半岛和西南极为红色，被冰层覆盖的海洋为白色。（Letter p. 459）封面图片提
供：USGS/NASA/Goddard Space Flight Center
地表温度季节性变化与自然变化的关系（Seasonal adjustments）
Changes in the phase of the annual cycle of surface temperature
地球表面温度季节性周期的变化在很多研究中都有反映，但这些变化在多达程度上能够
反映自然变化却仍不清楚。Stine等人通过在陆地和海洋上描绘这些季节性变化的空间
分布，同时通过将最近(1954-2007年)的变化趋势与早先（1900-1954年）所出现的趋势
进行比较，为回答这一问题提供了新线索。假设这一温度记录的前一部分是由自然变化
所主导的，那么最近的趋势似乎高度异常：陆地上的温度向早先的季节有1.7天的偏
移，而变化周期的幅度（即夏季和冬季之间的温差）在这一时期降低了。尽管这一现象
中所涉及的机制仍不确定，但对1954–2007年间陆地上的趋势所做测试表明，它们与自
然变化不一致，因此它们有可能是人类活动造成的。（Article p. 435; News &
Views）
肌动蛋白从G到F的构形变化（The G-to-F of actin）
The nature of the globular- to fibrous-actin transition
肌动蛋白存在于几乎所有真核细胞中，其形式有两种：细丝状F-肌动蛋白，它们驱动包
括细胞运动和肌肉收缩在内的很多细胞过程；以及它们由之而产生的单体，即球形或G-
肌动蛋白。在G-肌动蛋白向F-肌动蛋白转变的过程中所发生的结构变化仍然不清楚，因
为以前关于聚合物的模型一直在很大程度上以G-肌动蛋白的结构为依据。现在，F-肌动
蛋白的结构已以高分辨被确定。该结构显示，两个主要区域（它们在G-肌动蛋白中形成
一个推进器一样的缠绕结构）没有缠绕在一起，该分子在F-肌动蛋白中是平坦的。平坦
结构与螺旋形排列相结合，可稳定链内和链间的接触。从G到F的构形变化与以前关于肌
动蛋白的生物化学研究完全一致。（Article p. 441; News & Views）
同聚环ATP酶协调ATP水解及机制功能的方式（ATPases rings the changes）
Intersubunit coordination in a homomeric ring ATPase
同聚环ATP酶见于所有生命形式中，参与很多过程，如染色体分离、蛋白解折叠和ATP合
成。这种引人注目的功能多样性是由一个高度保留的结构核产生的，该结构核负责ATP
的结合和水解。但这些酶是怎样协调ATP水解及机制功能的却基本不清楚。其中一种这
样的环ATP酶来自一种名为phi29的噬菌体，它帮助将dsDNA基因组加载到病毒壳中。
Moffitt等人发现，这一由5部分组成的运动机制将DNA包装在由10个碱基对组成的“爆
发”中，每个“爆发”由4个包含2.5个碱基对的步骤组成，每个步骤相应于每个ATP的
水解。这样一个非整步的大小是前所未有的，它提出了关于环内ATP水解及ATP环与DNA
相互作用的有趣的机制问题。（Article p. 446; News & Views）
宇宙早期巨型星系高速形成恒星的原因（Early star formation: steady progress）
Cold streams in early massive hot haloes as the main mode of galaxy
formation
最近的观测表明，在100亿年前的年轻宇宙中，处在其恒星形成活动高峰阶段的巨型星
系形成恒星的速度之快令人吃惊。虽然这样的速度通常被归因于猛烈的星系合并，但很
多这些星系都是转动的盘，其延伸的范围同今天的银河系一样大，这种结构跟这样一个
历史是不一致的。一项新的宇宙模拟表明，这些星系是所谓的“流源”（stream fed）
性的，即从星系周围延伸的暗物质晕获取一个稳定的冷气体流，将其作为推动恒星形成
所需的物质。较为罕见的亚毫米星系（它们能够甚至更猛烈地形成恒星）才是基本上由
合并诱导产生的星暴（starbursts）。（Letter p. 451; News & Views）
“表面等离子激元”理想Q-因子的获得（An ideal Q-factor）
High-Q surface-plasmon-polariton whispering-gallery microcavity
人们对“表面等离子激元”的性质有浓厚兴趣，因为它们与等离子体光子学和纳米光子
学有关。它们是在金属和电介质材料界面上激发的电子密度波，在亚波长尺度上与光发
生强烈相互作用。它们实际应用的一个很好的出发点可以是具有高品质因子或高Q-值的
一个等离子微米腔或纳米腔。高品质因子意味着， “等离子激元”被严格约束在腔
内，在逃逸之前反弹很多次，从而导致丰富的物理性质。此前，“等离子激元”共振腔
的Q-因子对于可见和近红外波长一直限于低于100的数值。现在，Min等人演示了“表面
等离子激元”的一个高-Q值“回音廊”（whispering gallery）微米腔，该微米腔是通
过在高Q-值微共振器表面上涂上一薄层贵金属做成的。这种结构使得“表面等离子激
元”模能够在近红外波长以一个1,380左右的Q-因子进行室温操作，这是一个近乎理想
的数值。这项工作还包括一个耦合方案——让一个渐细的光纤处在与微米腔几乎要接触
的位置，这样可为选择性激发和探索“表面等离子激元”模提供一个方便的途径。
（Letter p. 455）
“铁蛋白”在海洋中所起的作用（Ferritin’s role in the oceans）
Ferritin is used for iron storage in bloom-forming marine pennate
diatoms
非血红素蛋白“铁蛋白”被很多植物、动物和微生物用来以一种非毒性可溶形式存储
铁，这种形式在需要时容易被利用。现在，“铁蛋白”已在两种硅藻中被发现，它们分
别是Pseudo-nitzschia 和 Fragilariopsis。这两种硅藻主导由以自然方式和人工方式
为海洋中补充铁所诱导的浮游植物繁盛现象。这是在“金黄藻菌鞭毛菌界”
（Stramenopila）任何一个成员中关于“铁蛋白”的首次报告。“金黄藻菌鞭毛菌界”
是真核生物的一个分支，包括很多浮游植物，如单细胞藻类、硅藻和大型藻类等。系统
发育分析表明，“铁蛋白”是通过侧向基因转移在硅藻的这一小类别中出现的，它也许
是它们在铁供应为初级生产力限制因素的30-40%的海洋中能够成功生存的关键。
（Letter p. 467）
“烟曲霉”被证实进行有性生殖（A long wait for sex）
Discovery of a sexual cycle in the opportunistic fungal pathogen
Aspergillus
fumigatus
真菌“烟曲霉”（Aspergillus fumigatus）在免疫系统受损的人体内是一个机会主义
的人类病原体，与严重哮喘和鼻窦炎有关。尽管越来越多的证据表明，“烟曲霉”存在
重组和基因流动，但此前在该物种中只观察到无性生殖。现在，在该真菌被定性145年
之后，它被发现是有性生殖的。本期Nature报告了有两个互补交配类型的分离菌种。这
一研究的意义包括，人们有可能进行经典的遗传分析，而这种分析又能帮助研究这种真
菌致病作用及对抗菌剂产生抵抗力的遗传基础。（Letter p. 471）
fMRI信号与脑活动及血流的关系（The brain thinks ahead）
Anticipatory haemodynamic signals in sensory cortex not predicted by
local
neuronal activity
关于脑活动的功能性核磁共振(fMRI)依赖于以下假设：脑中局部血流增加与脑中该区域
神经活动直接相关。Yevgeniy Sirotinand Aniruddha Das利用同步直接记录及fMRI对
猴子所做研究表明，这并不是故事的全部；部分fMRI信号与实际的脑活动无关。除了脑
互动这个因素外，还有脑中不太活跃区域因预期它们不久将会被用到而增加的血流。这
些发现向人们当前关于功能性脑成像信号的认识提出了挑战，并且还指出了脑中的一个
新颖的预测机制。（Letter p. 475; News & Views）
肠道细菌与胖瘦的关系（Obese and lean microbiota）
A core gut microbiome in obese and lean twins
人肠道中的很多“友好”细菌被认为与很多健康问题相关，尤其是那些涉及消化及易感
性的健康问题。对若干对成年女性双胞胎（所选研究对象既包括瘦的人，也包括胖的
人）粪便菌落所做一项研究显示，家族成员人肠道细菌之间有一些相似性，但每个人的
肠道菌落中所存在的具体细菌类别有所不同。不同个体之间有很多共享的细菌基因，在
基因层面上、而不是在微生物物种层面上包含一个可识别的“核心微生物组”。这个核
心包含很多用于碳氢化合物代谢的新颖基因，而且这个核心的偏差与一个人的胖瘦有
关。（Letter p. 480）
痘病毒与先天免疫系统的角力（Virus versus innate immunity）
Protein kinase R reveals an evolutionary model for defeating viral
mimicry
痘病毒（如天花）通过产生一种被称为K3L的蛋白来破坏宿主防卫系统。该蛋白能够非
常像地模仿“蛋白激酶R”（PKR）的基质，后者是脊椎动物先天免疫系统的一个重要组
成部分。Elde等人发现，PKR是在灵长类引人注目的积极选择过程中、通过在K3L 和
PKR相遇处替换氨基酸形成的。这些演化性变化增加了宿主挫败模仿的机会，其中两个
对手在进行一场分子“军备竞赛” ，试图通过斗智斗勇战胜对方。（Letter p. 485）
----------------------
NEWS AND VIEWS
----------------------
Neuroscience: Pre-emptive blood flow pp387-388
Electrical signalling among brain cells summons the local delivery of
extra
blood [mdash] the basis of functional brain imaging. Yet sometimes,
blood
is sent in anticipation of neural events that never take place.
David A. Leopold
doi:10.1038/457387a
http://www.nature.com/nature/journal/v457/n7228/full/457387a.html
Astrophysics: Galaxies in from the cold pp388-389
Computer simulations of the cosmos suggest that cold streams of gas
could
underlie the unexpectedly high star-formation activity of many
massive
galaxies found to exist a few billion years after the Big Bang.
Reinhard Genzel
doi:10.1038/457388a
http://www.nature.com/nature/journal/v457/n7228/full/457388a.html
Structural biology: Actin in a twist pp389-390
How monomers of the cytoskeletal protein actin join to form the
stable
polymers crucial to muscle contraction and cellular motility has been
a
long-standing question. A state-of-the-art approach provides an
answer.
Kenneth C. Holmes
doi:10.1038/457389a
http://www.nature.com/nature/journal/v457/n7228/full/457389a.html
50 & 100 years ago p390
doi:10.1038/457390a
http://www.nature.com/nature/journal/v457/n7228/full/457390a.html
Climate change: Shifts in season pp391-392
It's cold in winter and hot in summer. But the latest analysis
illustrates
the need to put observational data at the forefront of attempts to
achieve
a more detailed understanding of the annual temperature cycle.
David J. Thomson
doi:10.1038/457391a
http://www.nature.com/nature/journal/v457/n7228/full/457391a.html
Molecular biology: Concealed enzyme coordination pp392-393
Coordination between subunits is crucial for the proper functioning
of
multi-component molecular machines. A single-molecule study now
allows
glimpses into the mechanism used by subunits of one such machine.
Elio A. Abbondanzieri and Xiaowei Zhuang
doi:10.1038/457392a
http://www.nature.com/nature/journal/v457/n7228/full/457392a.html
Obituary: Daniel Carleton Gajdusek (1923-2008) p394
The most outlandish and peripatetic of microbe hunters.
Jaap Goudsmit
doi:10.1038/457394a
http://www.nature.com/nature/journal/v457/n7228/full/457394a.html
----------------------
INSIGHT
----------------------
INTRODUCTION
RNA silencing p395
Angela K. Eggleston
doi:10.1038/457395a
http://www.nature.com/nature/journal/v457/n7228/full/457395a.html
REVIEW ARTICLE
On the road to reading the RNA-interference code pp396-404
Haruhiko Siomi and Mikiko C. Siomi
doi:10.1038/nature07754
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07754.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07754.html
A three-dimensional view of the molecular machinery of RNA
interference
pp405-412
Martin Jinek and Jennifer A. Doudna
doi:10.1038/nature07755
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07755.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07755.html
Small RNAs in transcriptional gene silencing and genome defence
pp413-420
Danesh Moazed
doi:10.1038/nature07756
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07756.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07756.html
Viral and cellular messenger RNA targets of viral microRNAs pp421-425
Bryan R. Cullen
doi:10.1038/nature07757
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07757.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07757.html
The promises and pitfalls of RNA-interference-based
therapeutics pp426-433
Daniela Castanotto and John J. Rossi
doi:10.1038/nature07758
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07758.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07758.html
----------------------
ARTICLE
----------------------
Intersubunit coordination in a homomeric ring ATPase pp446-450
A ring ATPase from a bacteriophage, [phiv]29, helps load the dsDNA
genome
into the viral shell. It is shown that this motor packages the DNA in
10
base pair (bp) bursts, which are composed of four individual 2.5 bp
steps,
each representing hydrolysis of a single ATP. Such a non-integral
step
size is unexpected, and raises intriguing mechanistic questions about
ATP hydrolysis within rings.
Jeffrey R. Moffitt et al.
doi:10.1038/nature07637
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07637.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07637.html
----------------------
LETTERS
----------------------
A simple model of bipartite cooperation for ecological and
organizational
networks pp463-466
Networks of co-operative interactions occur in both ecological and
socio-
economic situations, with plant pollination by animals and
interactions
between manufacturing and contracting companies being respective
examples.
This work proposes a parsimonious model for co-operative networks
that
predicts the specific properties of real ecological and socio-
economic
networks, demonstrating that similar principles of co-operation might
underlie both situations.
Serguei Saavedra, Felix Reed-Tsochas and Brian Uzzi
doi:10.1038/nature07532
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07532.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07532.html
Ferritin is used for iron storage in bloom-forming marine pennate
diatoms
pp467-470
Natural or artificial oceanic iron supplementation induces blooms
that
are dominated by pennate diatoms. It is shown that these diatoms
contain
the iron storage protein ferritin, which may explain their success in
iron-limited waters.
Adrian Marchetti et al.
doi:10.1038/nature07539
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07539.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07539.html
Discovery of a sexual cycle in the opportunistic fungal pathogen
Aspergillus
fumigatus
Aspergillus fumigatus is an opportunistic human pathogen in
immunocompromised
individuals and is associated with severe asthma and sinusitis, and
has only
been known to reproduce asexually. This paper now shows that it can
reproduce sexually, for which isolates of complementary mating type
are
required.
Celine M. O/'Gorman, Hubert T. Fuller and Paul S. Dyer
doi:10.1038/nature07528
Abstract:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature07528.html?lan
g=en
Article:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature07528.html
A core gut microbiome in obese and lean twins pp480-484
The human microbiota has been implicated in many health-related
issues.
In this study, the microbiota composition of monozygotic and
dizygotic
twins and their mothers is examined. Although a core microbiome could
not be defined on a phylogenetic level, the data suggests that core
functions are conserved.
Peter J. Turnbaugh et al.
doi:10.1038/nature07540
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07540.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07540.html
Protein kinase R reveals an evolutionary model for defeating viral
mimicry pp485-489
This paper documents the evolutionary interaction between the innate
immunity gene protein kinase R (PKR), its substrate elF2[alpha], and
its poxvirus mimic K3L. It is concluded that the rapid evolution of
the PKR gene may be due to viral mimicry.
Nels C. Elde, Stephanie J. Child, Adam P. Geballe and Harmit S. Malik
doi:10.1038/nature07529
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07529.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07529.html
Endochondral ossification is required for haematopoietic stem-cell
niche formation pp490-494
This paper describes an in vivo assay of haematopoietic stem cell
(HSC) niche formation. A population of progenitor cells is sorted
from fetal bones, and when transplanted under the adult mouse kidney
capsule, the cells recruit host-derived blood vessels, produce donor-
derived ectopic bones, and generate a marrow cavity populated by host-
derived long-term reconstituting haematopoeitic stem cells.
Charles K. F. Chan et al.
doi:10.1038/nature07547
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07547.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07547.html
Pulsed contractions of an actin-myosin network drive apical
constriction
pp495-499
During gastrulation in Drosophila embryo, there is apical
constriction
of ventral cells, which results in formation of a ventral furrow and
invagination of the mesoderm. This study reports a mechanism for this
process and shows that apical constriction of ventral cells is
pulsed.
These pulses are powered by the actin-myosin contractions and are
dependent on the expression of a transcription factor, Snail, whereas
the constricted state is stabilized by the transcription factor Twist.
Adam C. Martin, Matthias Kaschube and Eric F. Wieschaus
doi:10.1038/nature07522
Abstract:
http://www.nature.com/nature/journal/v457/n7228/abs/nature07522.html?lang=en
Article:
http://www.nature.com/nature/journal/v457/n7228/full/nature07522.html
Discovery of a sexual cycle in the opportunistic fungal pathogen
Aspergillus fumigatus
Aspergillus fumigatus is an opportunistic human pathogen in
immunocompromised individuals and is associated with severe asthma
and sinusitis, and has only been known to reproduce asexually. This
paper now shows that it can reproduce sexually, for which isolates of
complementary mating type are required.
Celine M. O/'Gorman, Hubert T. Fuller and Paul S. Dyer
doi:10.1038/nature07528
Abstract:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature07528.html?lan
g=en
Article:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature07528.html