远缘杂交形成的二倍体鱼和多倍体鱼生殖细胞染色体研究

本文采用性腺染色体制片及组织学切片方法,系统地研究了不同发育时期的鲫鲤杂交第二代(F2) (2n=100)、异源四倍体鲫鲤(4n=200)、三倍体鲫鱼(3n=150))、雌核发育二倍体鲫鲤第二代(G2)(2n=100)及鲤鱼(Cypninus carpio L)(2n=100)(对照组)生殖细胞的染色体特征.研究结果表明,对照组中鲤鱼精原细胞染色体数与体细胞染色体数一致,为二倍体精原细胞(2n=100),而远缘杂交形成的二倍体鱼和多倍体鱼的生殖细胞中则观察到明显的染色体数加倍现象,其中,鲫鲤杂交第二代(F2)精巢生殖细胞染色体数加倍现象特别丰富,占检测的染色体分裂相的21.6%,为其产生不减半的二倍体配子提供了直接的细胞学证据,同时也说明远缘杂交是导致生殖细胞染色体数加倍的一个重要因素.该研究在探讨多倍体鱼的发生及鱼类遗传育种方面具有重要意义.     

大白菜与紫甘蓝种间杂种的获得与鉴定

以不同类型的大白菜与紫甘蓝为材料,运用蕾期授粉结合胚挽救技术获得大白菜与紫甘蓝的种间杂种,并对其进行细胞学鉴定.结果表明,大白菜与紫甘蓝杂交,获得了57株F1代幼苗;对根尖染色体数量进行观察和杂种花粉特性调查发现,其中47株具有预期的染色体数目,2n =19,鉴定为真杂种,其花粉败育;另有6株具有38条染色体,鉴定为种间异源双二倍体,应该是发生了染色体自然加倍,其花粉可育.可育的杂种F1代与大白菜回交,获得了大白菜-紫甘蓝BC1代材料.田间观测结果显示,杂种F1代植株综合性状均介于双亲之间,BC1代植株包球明显,综合性状偏向母本大白菜.     

水稻同源三倍体(149-B)×二倍体F2代稳定群体的验证及分析

14 9 B是由水稻多胚苗SAR 2中筛选出来的自然发生的同源多倍体 ,体细胞鉴定为三倍体 (2n =36 )。以14 9 B做母本与水稻恢复系蜀恢 36 3(R36 3)杂交 ,在杂交F1代中发现有非整倍体和二倍体个体产生 ,其中部分二倍体的自交后代在田间农艺性状表现稳定。对这个稳定F2群体进行微卫星验证 ,结果表明 :F1和F2 群体 4 0个单株的扩增带型整齐一致 ,在各个SSR多态位点只出现一条同父或同母带 ,丢失了来自父本或母本的等位位点 ,说明该F2 群体确系由杂交得来的一个早代稳定群体。     

百合‘Siberia’בManissa’种间杂交后代的染色体核型分析

以东方百合杂种系(Oriental hybrids group)品种‘Siberia’为母本,OT杂种系(interspecific hybrids betweenOriental and Longiflorum/OT group)品种‘Manissa’为父本杂交获得种间杂交F1代,对亲本及F1代株系的染色体数目和形态特征进行了分析。结果显示,母本东方百合‘Siberia’为二倍体即24条染色体,而父本‘Manissa’是高度杂合后代,为三倍体即36条染色体。杂交F1代的8个株系中有6个株系为二倍体即24条染色体,有2个株系为非整倍体,染色体条数分别为25和26条。母本‘Siberia’的核型为4m(1SAT)+10st(1SAT)+10t,父本‘Manis-sa’的核型为3m+18st(1SAT)+15t(1SAT),均属3B型。杂种F1代核型出现了多种类型,其中株系a、b、h为3B型,株系c、d、e、f为3A型,株系g为4B型。与亲本染色体形态相比,F1代株系出现了随体及端部着丝点染色体较多等染色体形态结构特征,而亲本没有这些特征。从染色体的形态、随体来看,子代为真杂种,在遗传上均偏向于母本。     

二倍体雌核发育鱼产生二倍体卵子的证据

二倍体雌核发育第 1代 (G1)产生的二倍体卵子经紫外线灭活的散鳞镜鲤精子诱导 ,无需染色体加倍处理 ,发育成二倍体雌核发育第 2代 (G2 ) ;G1 产生的二倍体卵子与雄性异源四倍体鲫鲤 (AT)产生的二倍体精子结合 ,形成新型两性可育的异源四倍体鲫鲤 (G1 ×AT)。对G2 和新四倍体 (G1 ×AT)的体细胞染色体数目、生殖细胞染色体行为及性腺结构、外形、生长速度等生物学特征进行了研究。结果表明 :G2 体细胞染色体数目为 2n =1 0 0。在 6～ 1 2月龄G2 中 ,没有发现性成熟的个体 ,组织学切片结果表明 ,G2 性腺处于卵原细胞增殖阶段 ,与 1龄G1 的性腺发育相似 ,性腺发育迟缓。对 6～ 8个月龄G2 性腺染色体制片进行观察 ,结果表明 ,G2 生殖细胞的染色体没有二价体的形成 ,只有有丝分裂的迹象 ,其有丝分裂中期不但有 2n =1 0 0的染色体分裂相 ,还有 4n =2 0 0的染色体分裂相 ,甚至有接近 8n(380 )的分裂相 ,说明 1龄G2 的性腺中存在 2n、4n等多种类型的生殖细胞 ,其中 4n的生殖细胞经正常的减数分裂后可产生二倍体卵子。核内复制 (pre meioticendoreduplication)学说可以较好地解释这种不减半配子产生的现象。新四倍体 (G1 ×AT)体细胞染色体数目为 4n =2 0 0 ,雌雄新四倍体 (G1 ×AT)具有正常的性腺发育 ,在繁殖季     

细胞学方法在木兰科杂交育种早期鉴定中的应用

研究了木兰科 1个属内种间杂交组合红花山玉兰 (Magnoliadelavayi) (♀ )×广玉兰(M grandiflora) (♂ )和 1个属间杂交组合红花山玉兰 (♀ )×乐东拟单性木兰 (Parakmerialotungensis) (♂ )的亲本及F1代的染色体数目和形态。结果表明 ,前者的杂交后代染色体数目为 76条 ,正好是二倍体红花山玉兰 (2n =2x =38)和六倍体广玉兰 (2n =6x =114 )的半数之和 ,且在F1代的分裂中期染色体具大小两种类型 ,可以明显看出来自红花山玉兰的染色体较大 ,而来自广玉兰的染色体较短小 ,这证明该F1为两者的杂交种 ;而后者的杂交后代染色体数仅为 38条 ,而不是二倍体山玉兰和六倍体乐东拟单性木兰 (2n =6x =114 )的半数之和 ,且所有染色体形态都与红花山玉兰相同这证明该F1代不是真正的杂交种 ,可能是无融合生殖的结果。本研究结果表明细胞学方法是木兰科植物杂交育种中早期检测的有效方法之一。     

甘蔗杂种的染色体和RAPD鉴定研究

采用体细胞染色体计数和RAPD (Random Amplified Polymorphism DNA) 分子标记的方法鉴定甘蔗与蔗茅属间杂交种F1的真实性.结果表明,杂种F1材料01/47、01/85、01/120的2n＝80～82,染色体遗传方式为n 2n.用110个随机引物进行RAPD扩增,63个引物可获得双亲的RAPD多态性,其中3个引物OPC-19、OPE-2、OPF-4可在杂种F1材料01/64和01/120的RAPD扩增标记中显示出双亲的特征谱带,分别为父本3500bp和母本1300bp、父本1350bp和母本900bp、父本550bp和母本900bp.     

不同倍性鱼的血细胞和精子DNA含量比较

我们以前的研究表明, 以红鲫 (2n=100) 为母本及湘江野鲤 (2n=100) 为父本的杂交后代的F1-F2 为二倍体 (2n= 100)。在二倍体 F2 个体中, 存在能分别产生二倍体卵子和二倍体精子的雌、雄个体, 二倍体卵子和二倍体精子结合, 形成了两性可育的四倍体鱼 (F3)。目前四倍体鲫鲤已连续繁殖了 12 代 (F3-F14), 形成了一个遗传性状稳定的四倍体鱼群体 (4n= 200) (Liu et al.,2001; 孙远东等, 2003)。雌性四倍体鲫鲤产生的二倍体卵子经紫外线照射的散鳞镜鲤精子激活后,无须染色体加倍处理, 可发育为全雌性二倍体雌核发育后代 (G1) (2n=10…     

玉米与四倍体多年生玉米代换种质的选育及其基因组原位杂交鉴定

通过对玉米与四倍体多年生玉米杂种F1采用遮光调节开花时期、喷施低浓度赤霉素等提高可杂交性措施 ,选育出一个含有四倍体多年生玉米遗传物质的、在形态特性与普通玉米相似的种质 ,并对供试材料的表型性状进行了调查 ,对玉米及其与四倍体多年生杂交后代材料的体细胞染色体进行多色基因组原位杂交 (Multi colorGenomeinsituHybridization ,McGISH)检测。结果表明 :玉米与四倍体多年生玉米种杂交后代F2 ×P1的许多表型性状已经回复到玉米的特征 ;F2 ×P1自交一代 (BC1F3 )染色体数目为 2 0 ,在原位杂交检测的植株中有 17条与玉米亲本显色相同 ,另外 3条染色体区别于玉米基因组 ,检出为红色荧光且形态上小于玉米染色体 ,表明其来源于四倍体多年生玉米染色体。可见 ,BC1F3 是玉米 四倍体多年生玉米异源代换种质。     

Ogura细胞质雄性不育紫菜苔×萝卜属间杂种F1的获得及细胞遗传学研究

以Ogura细胞质雄性不育紫菜苔(AA,2n＝20)为母本,以不同萝卜品种(RR,2n＝18)为父本进行杂交,获得了大量的属间杂种.杂种F1幼苗在低温下子叶及真叶均不缺绿.以红萝卜为父本获得的杂种F1植株叶柄、叶脉呈紫红色;以白萝卜为父本获得的杂种F1植株叶柄、叶脉不呈紫红色.所有的杂种F1植株都开白花,蜜腺正常,雄配子高度不育,但是雌配子具有部分育性.杂种F1花粉母细胞的染色体数目为预期的2n＝19,染色体平均配对构型为15.53+1.34+0.25+0.01,多数染色体以单价体的形式存在,但也有一些二价体、三价体甚至四价体,最多达到6+3+1,参加配对的染色体数达到13条,表明A染色体组和R染色体组具有一定的同源性.对该杂种的遗传及育种意义进行了讨论.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细