Epigenetic aspects of X-chromosome dosage compensation

The X chromosomes of mammals and fruit flies exhibit unusual properties that have evolved to deal with the different dosages of X-linked genes in males (XY) and females (XX). The X chromosome dosage-compensation mechanisms discovered in these species are evolutionarily unrelated, but exhibit surprising parallels in their regulatory strategies. These features include the importance of noncoding RNAs, and epigenetic spreading of chromatin-modifying activities. Sex chromosomes have posed a fascinating puzzle for biologists. The dissimilar organization, gene content, and regulation of the X and Y chromosomes are thought to reflect selective forces acting on original pairs of identical chromosomes (1-3). The result in many organisms is a male-specific Y chromosome that has lost most of its original genetic content, and a difference in dosage of the X chromosome in males (XY) and females (XX).     

内蒙古白绒山羊染色体核型初步分析

本文采用外周血淋巴细胞短期培养方法,对内蒙古白绒山羊染色体进行了核型分析。分析结果表明,内蒙古白绒山羊的二倍体细胞染色体数目为2n=60。其中有29对常染色体和1对性染色体(xy 型)。所有的染色体均为端部着丝点染色体。     

芦笋性染色体的细胞学研究

采用去壁低渗法,对芦笋的茎尖的核型进行了研究,结果表明,芦笋的性别决定方式为XY型,雄株为XY,其核型公式为2n=2x=20=13m(2SAT)+7sm(SAT);雌株为XX,其核型公式2n=2x=20=12m(2SAT)+8sm;核型类型为2B型,属于较原始的类型。对芦笋花粉母细胞的减数分裂过程进行观察,发现存在1对不能完全配对的二价体,并且染色体在由前Ⅰ期向中Ⅰ期转变过程中,可以看到1对提前分离的染色体。确定了芦笋的性别决定方式属于异型XY型性别决定方式。     

蒙古马染色体核型初步分析

本文采用外周血淋巴细胞短期培养方法,对蒙古马染色体进行了核型分析。分析结果表明,蒙古马的二倍体细胞染色体数为2n=64。其中有31对常染色体和1对性染色体(XY型)。31对常染色体中有13对为中部着丝点染色体和18对为端都着丝点染色体。X为近中着丝点染色体,Y为端部着丝点染色体。     

双峰驼染色体核型初步分析

我们采用双峰驼的外周血液淋巴细胞培养方法,对其染色体进行了分析研究。研究结果表明,双峰驼的染色体数目为 2n=74。并初步摸索出一个比较易行的培养操作过程,为进一步开展骆驼遗传结构研究提供了参考材料.     

Water rights, gender, and poverty alleviation. Inclusion and exclusion of women and men smallholders in public irrigation infrastructure development

Governmental and non-governmentalagencies worldwide have devoted considerablefinancial, technical, and organizational efforts toconstruct or rehabilitate irrigation infrastructure inthe last three decades. Although rural povertyalleviation was often one of their aims, evidenceshows that rights to irrigated land and water wererarely vested in poor men, and even less in poorwomen. In spite of the strong role of irrigationagencies in vesting rights to irrigated land and waterin some people and not in others, the importance ofagencies targeting practices is still ignored.This article disentangles how public irrigationagencies either included or excluded women and mensmallholders as right holders to irrigated land andwater. This is done on the basis of significant casestudies from Africa, Asia, and Latin America thatpoint in both positive and negative directions. Thegeneral conclusions are the following. Rights toirrigated land are related to the site-selection andphysical design of land-bound irrigationinfrastructure. These rights are vested in the pooreither by implementing a localized land reform or bydirectly selecting poor peoples land forimprovement. Among all potential land users in aselected site, water rights have to be defined. Thepoor are included as title holders if water rights arevested in land users rather than land owners, and inboth women and men, rather than in male householdheads. A common condition to get water rights is thatone has to participate in construction investments.Agencies need, firstly, to open up this condition forthe poor, also for women, and, secondly, ensure thatpoor peoples investments are linked to rights.Parallel to vesting land and water rights, externalagencies influence the composition of the local forumsin which decisions on land and water rights arerefined, endorsed, and implemented, and they influencethe order in which project activities are planned andundertaken. Early inclusion of the poor in theseforums and crystallization of expropriation andallocation criteria and procedures before constructionstarts are pivotal for poverty alleviation.     

滩羊染色体组型的研究

应用血液白细胞培养法对滩羊的核型进行研究,结果证实滩羊染色体数2n=54,其中有26对常染色体和1对性染色体(xx/xy型)。26对常染色体中有3对为最大的中部着丝点染色体和23对端部着丝点染色体;x为最大的端部着丝点染色体,y为最小的中部着丝点染色体。我们初步认为湖羊、滩羊和蒙古羊的起源相同。     

关中马的染色体核型分析

采用外周血淋巴细胞培养法 ,对关中马的染色体核型进行了研究。结果表明 ,关中马的二倍体染色体数目为 2 n=6 4,公马核型为 6 4,XY;母马核型为 6 4,XX,包括 31对常染色体和 1对性染色体。 31对常染色体中 ,13对为中部或亚中部着丝点染色体 ,18对为端部着丝点染色体 ;1对性染色体中 ,X染色体为 1条第二大的亚中部着丝点染色体 ,Y染色体为最小的端部着丝点染色体。     

双峰驼染色体组型分析

我们采用外周血淋巴细胞培养方法对双峰驼的染色体进行了分析。结果初步证实染色体数为2n=74,常染色体36对,臂数NF=132;性染色体一对,组成为xx/xy型。36对常染色体中有15对为亚端着丝点,9对为亚中着丝点,6对端部着丝点和6对中部着丝点。x染色体为中部着丝点,y染色体为端部着丝点。     

海门白山羊染色体核型研究及C-带分析

采用外周血淋巴细胞培养及染色体分带技术,分析了海门白山羊的染色体核型与C-带。结果表明,海门白山羊二倍体染色体数为2n=60,常染色体和X染色体均为端部着丝粒染色体,X染色体的大小介于1号和2号染色体之间,Y染色体最小,为中部着丝粒染色体,公羊核型为60,XY,母羊为60,XX。大部分常染色体和X,Y染色体着丝粒部位显示阳性C-带,但不同染色体的阳性C-带区域大小不同。     

Sexual selection can resolve sex-linked sexual antagonism

Sexual selection is a potent evolutionary force. However, very few models have considered the evolution of female preferences for traits expressed in both sexes. Here we explore how female preferences coevolve with sexually antagonistic traits, which involve alleles that are beneficial to one sex but harmful to the other. We show that with a sexually antagonistic trait on the X chromosome (males XY, females XX), females evolve to prefer mates carrying alleles beneficial to daughters. In contrast, with a Z-linked trait (males ZZ, females ZW), females more often evolve mating preferences for mates carrying alleles beneficial to sons (that is, flashy displays).     

小单孢菌属X46马唐致病菌的筛选

[目的]研究小单孢菌属X46马唐致病菌的筛选方法及致病作用。[方法]采用改良的高氏I号培养基从马唐、稗草根际土壤中分离出1株马唐致病菌X46,对其最优化产毒素条件进行测定并对其安全性进行评估。[结果]经鉴定,马唐致病菌X46为小单孢菌属;其最优化培养条件为：在高氏I号培养液中,300ml三角瓶装液量30ml,初始pH值6.0～6.5,采用10%接种量,180r/min28℃发酵120h即可使毒素产生量最大。该菌对玉米、番茄和黄豆具有明显的促生长作用,对小麦有轻微的抑制作用,对黄瓜生长抑制作用明显。[结论]X46是一株具有开发为中国北方用生物除草剂的潜力菌株。     

Transient homologous chromosome pairing marks the onset of X inactivation

Mammalian X inactivation turns off one female X chromosome to enact dosage compensation between XX and XY individuals. X inactivation is known to be regulated in cis by Xite, Tsix, and Xist, but in principle the two Xs must also be regulated in trans to ensure mutually exclusive silencing. Here, we demonstrate that interchromosomal pairing mediates this communication. Pairing occurs transiently at the onset of X inactivation and is specific to the X-inactivation center. Deleting Xite and Tsix perturbs pairing and counting/choice, whereas their autosomal insertion induces de novo X-autosome pairing. Ectopic X-autosome interactions inhibit endogenous X-X pairing and block the initiation of X-chromosome inactivation. Thus, Tsix and Xite function both in cis and in trans. We propose that Tsix and Xite regulate counting and mutually exclusive choice through X-X pairing.     

甘肃白猪性畸形及其对生产性能的影响

为了配合育种工作,作者采用常规染色体制备方法,对96头甘肃白猪及其杂交猪的染色体作了研究。检出核型为38,XY的雌性个体2头。染色体G—带和性染色质分析的结果表明它们具有1条Y染色体和1条X染色体。对这2头间性个体的肥育性能、胴体成绩和肉品质三项指标测定结果表明,间性个体与正常个体无显著差异。由于这2头个体均与武武品系有关,所以在这一品系的选育中应给予高度重视。     

尼罗罗非鱼X和Y染色体原位杂交探针的制备

通过染色体显微切割的方法，分别从尼罗罗非鱼XX和YY个体有丝分裂中期相染色体滴片上，割取第1对染色体，随后经简并PCR扩增，分别用生物素和地高辛标记，得到X和Y染色体探针。将探针与尼罗罗非鱼XY个体的染色体进行荧光原位杂交，在第1对染色体上得到很强的杂交信号。结果表明，染色体显微切割和简并PCR技术相结合，可以有效地制备鱼类DNA探针。     

青杨脊虎天牛对伴生真菌的触角电位反应

为了探索伴生真菌在青杨脊虎天牛寄主选择过程中的作用,利用触角电位法(EAG)测试了青杨脊虎天牛对伴生的46株真菌的触角电位反应。结果表明:有11个菌株能够引起青杨脊虎天牛雌成虫明显的EAG反应,其中6个菌株与对照相比差异极显著;雌成虫对2株腐皮镰刀菌(Fusarium solani(Mart.)Sacc.)具有较强的EAG反应,EAG最高相对均值达201.67%和199.00%,约为对照的2倍,差异极显著;有17个菌株能够引起青杨脊虎天牛雄成虫明显的触角电位反应,其中3个菌株与对照相比差异极显著。     

Regulation of X-chromosome counting by Tsix and Xite sequences

In mammals, X-inactivation establishes X-chromosome dosage parity between males and females. How X-chromosome counting regulates this process remains elusive, because neither the hypothesized inactivation "blocking factor" nor the required cis-elements have been defined. Here, a mouse knockout and transgenic analysis identified DNA sequences within the noncoding Tsix and Xite genes as numerators. Homozygous deficiency of Tsix resulted in "chaotic choice" and a variable number of inactive X's, whereas overdosage of Tsix/Xite inhibited X-inactivation. Thus, counting was affected by specific Tsix/Xite mutations, suggesting that counting is genetically separable from but molecularly coupled to choice. The mutations affect XX and XY cells differently, demonstrating that counting and choice are regulated not by one "blocking factor," but by both a "blocking" and a "competence" factor.     

河西制种基地玉米杂交种种子成熟期与种子活力的关系

【目的】研究河西制种基地玉米杂交种种子成熟度与种子活力的关系,确定高活力种子的适宜收获期,为种子企业躲避早秋霜冻提供依据。【方法】选择硬粒型先玉335、马齿型郑单958和吉祥1号3个杂交种制种田,授粉后每隔3-5 d采集果穗测定籽粒水分,实验室进行标准发芽和冷浸抗冷试验,测定种子发芽率和浸出液电导率,籽粒乳线发育按5级分类法记录：1=整个胚乳是液体状,无乳线;2=种子长度的25%充满硬化胚乳层,乳线出现在离种子顶部1/4处;3=种子长度的50%充满硬化胚乳层,乳线出现在种子1/2处;4=种子长度的3/4含硬化胚乳层,乳线下移到接近种子基部;5=整个种子是硬化的胚乳层,乳线消失。【结果】不同玉米杂交种、授粉后不同采收期对籽粒水分、脱水速率、种子发芽率和活力影响达到极显著水平,先玉335脱水早、脱水快,授粉后32 d时籽粒水分比郑单958、吉祥1号低10%-15%,授粉后32-75 d随着灌浆的进行果穗籽粒水分递减,平均生理脱水速率先玉335（0.70%/d）高于郑单958（0.62%/d）和吉祥1号（0.49%/d）,籽粒水分每减少1%,先玉335、郑单958和吉祥1号百粒重依次增加0.73 g、0.50 g、0.29 g。不同采收期种子成熟度和种子活力有较大差异,籽粒水分为70%-40%,随着水分降低,种子发芽率增加、浸出液电导率减少,水分每减少1%,先玉335、郑单958和吉祥1号发芽率依次提高3.37%、2.76%、1.67%。随着灌浆时间推后,籽粒发芽率增加、电导率降低,但杂交种之间有一定差异,授粉后32 d 3个杂交种标准发芽率为30.0%-59.0%,6℃冷浸3 d发芽率为2.5%-36.9%,授粉47 d以后先玉335冷浸芽率与标准发芽率接近,而郑单958、吉祥1号冷浸发芽率始终明显低于标准发芽率,即种子抗低温能力大小为先玉335＞郑单958＞吉祥1号。种子发育过程中籽粒水分与乳线发育明显相关,随着水分减少乳线下移,先玉335籽粒乳线出现早、消失也早,郑单958次之,吉祥1号乳线出现最迟、消失最晚,乳线发育到籽粒1/2处时,籽粒水分降到38%-40%,种子标准发芽率和冷浸发芽率均接近较高值,此时先玉335、郑单958百粒重占生理成熟时最大百粒重的76.6%和88.0%。【结论】玉米种子成熟度影响种子活力大小,发芽率和活力最大的采收期宜在乳线到籽粒中部位置,此时籽粒水分40%左右,而不是干物质达到最大的生理成熟期,甘肃武威制种基地先玉335高活力种子的适宜采收期开始于授粉后47 d,而郑单958和吉祥1号在授粉后60 d,比目前生产收获期提前10-15 d,可避免早霜冻对玉米种子质量的影响。     

Constructing “green” foods: Corporate capital, risk, and organic farming in Australia and New Zealand

Public concern over environmentalquality and food safety has culminated in thedevelopment of markets for green foods – foodsthat are variously construed as fresh, chemical-free,nutritious, natural, or produced in anenvironmentally-sustainable manner. Understanding theemergence of green foods is dependent on analysisboth of the ways in which foods are produced andprocessed, and of the meanings that are attached tothem at each stage of their production,transformation, and consumption. The notion of greenfoods is thereby understood here as a fluid andcontestable signifier that myriad actors involved inthe production/consumption cycle may attempt to shapefor their own purposes. This paper explores corporate capital's recent attempts, through certification logosand advertising, to signify the healthiness andenvironmental virtues of organically-produced foods inAustralia and New Zealand. These attempts have not,however, been universally successful either in termsof gaining consumer interest, or in gaining agreementsbetween farmers, certifying organizations, andcapitalist firms over the meaning of organic and thepractice of sustainable agriculture. The experienceof corporate involvement in the organics industry isillustrative of yet-to-be-resolved processes ofreflexive modernization. As food production andtransformation continues to produce environmental andsocial risks, the question of just what makes foodgreen will continue to be a source of social conflict.