物种形成基因及其功能

什么是物种?新物种是如何形成的？这些问题是生命科学研究的重大问题.物种的形成是在生殖隔离的基础上某些新的生物学性状的形成和保留,是生物进化的最基本过程,其实质是基因结构突变的积累与功能的分化. 地理隔离使群体中的基因不能交流,基因突变也会影响个体间交配趣向,从而造成交配隔离或者交配后杂合体的基因组不亲和、杂交不育甚至杂交不活,使不同的群体逐渐分化为新物种. 随着分子生物学与基因组学的飞速发展,进化生物学家已经发现一些与物种形成有关的基因-物种形成基因（speciation genes）,鉴定并了解这些基因的功能,不仅能使我们在分子水平上理解新物种形成的实质和规律、而且对于我们突破种间屏障进行远缘杂交育种也有重要的理论指导意义.本文综述了目前对几个物种形成基因及其功能的研究进展,为该领域的进一步研究提供资料.     

Sucrose-induced Autolysis and Development of Protoplast-like Cells of Clostridium saccharoperbutylacetonicum

A growing culture of Clostridium saccharoperbutylacetonicum partially lost its turbidity in the presence of 0.3 to 0.6 m sucrose without any extraneous supplements for cell wall degradation. The maximum effect was shown at 0.35 m of sucrose and the culture lost 40 to 50% of initial turbidity. The rate of lysis depended on the age of culture. The most rapid lysis occurred in the organisms of early exponential growing cultures, but no lysis was observed on those of late exponential and stationary phase cultures. The optimal pH was 5.5 to 6.0, and the optimal temperature 30 to 35°C. The sucrose-induced lysis was inhibited by bivalent cations (such as Ca²⁺, Mg²⁺), heavy metal cations (such as Cu²⁺, Pb²⁺), enzymic inhibitors (such as PCMB) and fixative agents (such as formalin, glutaraldehyde), while organisms whose growth had been inhibited by antibiotics (such as chloramphenicol, tetracycline) were also resistant to sucrose-induced lysis. The sucrose-induced lysis was accompanied by striking morphological conversion from original rod cells (3.0~6.0}0.4~0.6 μ) to spherical cells (1.0~ 1.2 μ diameter). The sucrose-induced lysis was also observed on the relative strains of C. saccharoperbutylacetonicum and C. sporogenes, but not observed on many other species of Clostridium and aerobic bacteria tested. It was suggested that sucrose-induced lysis was a kind of bacterial autolysis which was induced by sucrose treatment. The bacterial spheres developed during the lysis may be the protoplasts.     

利用放射杂交克隆板进行猪FMR1等5个基因间的连锁分析

放射杂交技术在人类图谱（包括ESTs、STSs和微卫星）的构建中已证明是一种非常有效的方法。根据人类基因组X染色体上FMR1、IDS、FATE、BGN、F8A等5个基因的信息资源,用已构建的猪/仓鼠96个放射杂交细胞系分析猪染色体该5个基因间的连锁关系。结果显示：当LOD值为4时,FMR1、IDS、FATE、BGN、F8A都处于同一个连锁群内;当LOD值为5时,FMR1、IDS处于同一个连锁群,FATE和BGN在同一个连锁群内,而F8A单独处于一个连锁群中。     

应用RH技术定位人胎肝的7个新基因

辐射杂交细胞系（RH）技术是一种体细胞遗传学技术,是继荧光原位杂交技术（FISH）后新建立的染色体定位方法。本文应用该技术将发现于22周孕龄人胎肝的7个新基因进行了染色体定位：肝细胞生成素（hepatopoietin,HPO）定位于Chr.16q22.1～22.3,HQ0508定位于Chr.22q13.31～13.32,HQ0750定位于Chr.11q24.3,HQ0915定位于Chr.16p13.3,HQ1880定位于Chr.11q13.2～13.4,HQ2180定位于Chr.19q13.2～13.3,HQ3091定位于Chr.12q21.33。 Abstract：Seven novel genes, which were isolated from human fetal liver (22weeks) cDNA library, were successfully mapped to their appropriate chromosomal positions by using radiation hybrid (RH) panel. The novel gene HPO was mapped to Chr.16q22.1～22.3, HQ0508 to Chr.22q13.31～13.32, HQ0750 to Chr.11q24.3, HQ0915 to Chr.16p13.3, HQ1880 to Chr.11q13.2～13.4, HQ2180 to Chr.19q13.2～13.3, and HQ3091 to Chr.12q21.33, respectively.     

Hybrid Ia antigens: Genetic,serologic, and biochemical analyses

Ia specificities 22 and 23 were found to be determinants on hybrid Ia molecules, formed by the noncovalent binding of a 26,000–28,000 dalton beta polypeptide chain (A_e) coded by the I-A subregion and a 32,000–35,000 dalton alpha chain (E_α) coded by the I-E subregion. For expression of Ia. 23 the A_e chain, coded by the I-A subregion, must be derived from the H-2^d haplotype, while A^b, A^s, or A^k can provide the complementing beta chain for the expression of Ia. 22. For expression of Ia. 22 and Ia. 23, most Ia. 7 positive strains can provide the complementing alpha chain (E_α), with the one exception of B 10. PL (E^u), which is Ia. 7 positive but will not complement with A^d to express Ia. 23. Antisera were also produced against hybrid Ia antigens by immunizing with F₁ cells expressing Ia. 22 or Ia. 23 generated by transcomplementation. These antisera detect the same specificities as conventional anti-Ia. 22 and anti-Ia. 23 sera produced against cis-complementing Ia antigens. It is postulated that hybrid Ia determinants are involved in recognition and generation of immune response to antigens under dual Ir gene control. It is also suggested that there are 2 types of Ia specificities: (1) allotypic Ia specificities expressed on the alpha or beta chains (for example, Ia. 7 on the E_α chain) and (2) hybrid Ia specificities, which are unique interaction determinants formed by the association of alpha and beta chains (for example, Ia. 22 and Ia. 23). These interaction gene products may be involved in antigen recognition and presentation.     

人细胞生长相关5个新基因的染色体定位及其基因结构

基因的染色体定位对我们研究基因相互关系、基因的组织与进化及理解基因与疾病关系具有重要的意义。本文采用RH-PCR方法及生物信息学方法对PP3898、PP1158、PP753、SP260、HC56等5条人细胞生长相关新基因进行染色体定位,并分析了其基因结构。PP3898及PP1158定位于19p13.3,PP753及SP260定位于1q21.1,HC56定位于17p13.3。PP3898含有19个外显子和18个内含子,可读框为2565bp;PP1158含有7个外显子和6个内含子,可读框为1218bp;SP260含有10个外显子和9个内含子,可读框为690bp;HC56为单外显子,可读框为3141bp。另外,对染色体定位获得的信息进行了分析。 Abstract:Five novel human genes related to cell growth control were newly isolated and identified by high-throughput functional screening.In this paper,the chromosomal localization of these five genes is reported.Radiation hybrid mapping and in silico mapping,and their genomic organization were analyzed respectively.PP3898 and PP1158 were assigned to chromosome 19p13.3,SP260 and PP753 to chromosome 1q21.1,and HC56 to chromosome 17p13.3.PP3898 contains nineteen exons and eighteen introns,PP1158 seven exons and six introns,SP260 ten exons and nine introns,and HC56 only one exon.The implications of chromosomal localization are discussed.     

New gene assignments using a complete, characterized sheep-hamster somatic cell hybrid panel

The generation and characterization of new sheep-hamster cell hybrids is reported from the fusion of sheep white blood cells with six different hamster auxotrophs. Selection from these and previously generated cell hybrids has led to the production of a panel of 30 hybrids covering the complete sheep genome of 28 chromosomes. Over half of the cell hybrids in this panel contain single sheep chromosomes. By complementation, the following new assignments have been made using the panel: phosphoribosyl N-formylglycinamide amidotransferase (PRFGA) to sheep chromosome (chr) 11; adenylosuccinate synthetase (ADSS) to sheep chr 12; adenylosuccinate lyase (ADSL) to sheep chr 3q; 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGCS) to sheep chr 16; dihydrofolate reductase (DHFR) to sheep chr 5; and adenine phosphoribosyltransferase (APRT) to sheep chr 14. The gene phosphoribosylaminoinidazole-carboxamide formyltransferase/Inosinicase (PRACFT) has now been regionally assigned to chr 2q. By isozyme analysis, phosphogluconate dehydrogenase (PGD) was assigned to sheep chr 12, anchoring the sheep syntenic group U1 to this chromosome, and mannose phosphate isomerase (MPI) was assigned to sheep chr 18. Furthermore, the chromosomal assignment of 110 microsatellites was confirmed using this cell panel.     

Sheep gene mapping: assignment of ALDOB, CYP19, WT and SOX2 by somatic cell hybrid analysis

Twenty-four hamster-sheep hybrid cell lines representing eleven ovine synteny groups were used to make syntenic assignments for seven loci ALDOB (aldolase B, fructose biphosphate); AMH (anti-Müllerian hormone); CYP19 [cytochrome P₄₅₀ aromatase, subfamily XIX (aromatization of androgens)]; WT (Wilms' tumour gene); SOX2 (SRY-related HMG-box gene 2); FSHB (follicle-stimulating hormone, beta polypeptide); and SRY (sex region of Y chromosome). These loci were assigned to synteny groups U11(chr2) ( ALDOB ); U19 ( AMH ); U3(chr7) ( CYP19 ); and to chromosomes 15 ( WT ) and 1 ( SOX2 ). SRY defines the hybrids containing the Y chromosome.     

Recombinant hybrids retain heterozygosity at many loci: new insights into the genomics of reproductive isolation in Populus

The maintenance of species barriers in the face of gene flow is often thought to result from strong selection against intermediate genotypes, thereby preserving genetic differentiation. Most speciation genomic studies thus aim to identify exceptionally divergent loci between populations, but divergence will be affected by many processes other than reproductive isolation (RI) and speciation. Through genomic studies of recombinant hybrids sampled in the wild, genetic variation associated with RI can be observed in situ, because selection against incompatible genotypes will leave detectable patterns of variation in the hybrid genomes. To better understand the mechanisms directly involved in RI, we investigated three natural ‘replicate’ hybrid zones between two divergent Populus species via locus‐specific patterns of ancestry across recombinant hybrid genomes. As expected, genomic patterns in hybrids and their parental species were consistent with the presence of underdominant selection at several genomic regions. Surprisingly, many loci displayed greatly increased between‐species heterozygosity in recombinant hybrids despite striking genetic differentiation between the parental genomes, the opposite of what would be expected with selection against intermediate genotypes. Only a limited, reproducible set of genotypic combinations was present in hybrid genomes across localities. In the absence of clearly delimited ‘hybrid habitats’, our results suggest that complex epistatic interactions within genomes play an important role in advanced stages of RI between these ecologically divergent forest trees. This calls for more genomic studies that test for unusual patterns of genomic ancestry in hybridizing species.     

A novel thiolase-reductase gene fusion promotes the production of polyhydroxybutyrate in Arabidopsis

The production of polyhydroxybutyrate (PHB) involves a multigene pathway consisting of thiolase, reductase and synthase genes. In order to simplify this pathway for plant-based expression, a library of thiolase and reductase gene fusions was generated by randomly ligating a short core linker DNA sequence to create in-frame fusions between the thiolase and reductase genes. The resulting fusion constructs were screened for PHB formation in Escherichia coli. This screen identified a polymer-producing candidate in which the thiolase and reductase genes were fused via a 26-amino-acid linker. This gene fusion, designated phaA-phaB, represents an active gene fusion of two homotetrameric enzymes. Expression of phaA-phaB in E. coli and Arabidopsis yielded a fusion protein observed to be the expected size by Western blotting techniques. The fusion protein exhibited thiolase and reductase enzyme activities in crude extracts of recombinant E. coli that were three-fold and nine-fold less than those of the individually expressed thiolase and reductase enzymes, respectively. When targeted to the plastid, and coexpressed with a plastid-targeted polyhydroxyalkanoate (PHA) synthase, the fusion protein enabled PHB formation in Arabidopsis, yielding roughly half the PHB formed in plants expressing individual thiolase, reductase and synthase enzymes. This work represents a first step towards simplifying the expression of the PHB biosynthetic pathway in plants.     

蛙皮素-蜂毒素杂合肽基因在大肠杆菌中的克隆与诱导表达

抗菌肽 (Ａｎｔｉｂａｃｔｅｒｉａｌｐｅｐｔｉｄｅｓ)原指昆虫体内经诱导产生的一类分子量在 4ｋＤ左右 ,具有抗菌活性的碱性多肽物质[2 ] 。这类抗菌剂最初是从昆虫、哺乳动物、两栖动物等的防御系统中分离得到的。抗菌肽对革兰氏阳性及阴性细菌、病毒、原虫和发生病变的真核细胞等有杀伤作用 ,具有很强的广谱抑菌作用 ,但对正常哺乳动物细胞无杀伤作用[3 ] 。蛙皮素还具有抗肿瘤活性而没有溶血活性[4 ] ,虽然蜂毒素具有溶血活性 ,但其溶血功能区位于Ｃ端的亲水区域[5] ,两者的极性区域正好相反。据研究表明抗菌肽都会形成两亲螺旋结构的…     

Application of radiation hybrid in gene mapping

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Sheep gene mapping: additional DNA markers included (CASB, CASK, LALBA, IGF-1 and AMH).

DNA extracted from 25 hamster-sheep hybrid cell lines was subjected, after Southern blotting, to hybridization with CASB, CASK, LALBA, IGF-1 and AMH cDNA probes. CASB and CASK segregated together and IGF-1 and LALBA were found syntenic with the LDHB-PEPB-TPI-GAPD-SHMT-KRTB group. No other synteny was observed with any of the previously described groups using the same hybrid cell panel. Gene nomenclature: ACO 1: aconitase 1 (soluble); ADA: adenosine deaminase; AMH: antiMüllerian hormone; ARA 1: murine sarcoma 3611 viral (v-raf) oncogene homologue 1; CASB: beta-casein; CASK: kappa-casein; ENO 1: enolase 1 (alpha); G6PD: glucose-6-phosphate dehydrogenase; GALA (or GLA): glactosidase (alpha); GAPD: glyceraldehyde -3- phosphate dehydrogenase; GPI: glucose phosphate isomerase; GSR: glutathione reductase; HBG: haemoglobin gamma; HPRT: hypoxanthine phosphoribosyl transferase; IDH 1: isocitrate dehydrogenase 1 (soluble); IGF-1: insulin growth factor 1; ITPA: inosine triphosphatase; KRTA: keratin (acid); KRTB: keratin (basic); LALBA: alpha-lactalbumin; LDHA: lactate dehydrogenase A; LDHB: lactate dehydrogenase B; MDH 2: malate dehydrogenase NAD (soluble); ME 1: malic enzyme (soluble); MPI: mannose phosphate isomerase; NP: nucleoside phosphorylase; OLA: ovine leucocyte antigen; OTC: ornitine carbamoyltransferase; PAIS: phosphoribosyl amino imidazole synthetase; PEPA, PEPB, PEPC: peptidase A, B, C; PGD: phospho gluconate dehydrogenase; PGK: phosphoglycerate kinase; PGM 3: phospho glucomutase 3; PKM 2: pyruvate kinase (muscle); PLP: proteolipid protein; PRGS: phosphoribosyl glycinamide synthetase; RCP: red cone pigment; SHMT: serine hydroxymethyl transferase; SOD 1: superoxide dismutase 1 (soluble); SYN 1: synapsin 1; TPI l: triose phosphate isomerase 1.     

Two sequence alterations,a 136 bp InDel and an A/C polymorphic site,in the S5 locus are associated with spikelet fertility of indica-japonica hybrid in rice

The rice indica/japonica hybrid shows strong heterosis.However,such inter-subspecific hybrid can't be directly used in rice production due to its low spikelet fertility.The S5 locus was proved to be associated with fertility of indica/japonica hybrid and its S5n allele from wide-compatibility variety(WCV)is capable to overcome fertility barrier.In the present study,we reported the causal sites in the S5 locus responsible for compatibility of indica/japonica hybrid.Fine-mapping of the S5 locus using the 11 test-cross families pinpoints a candidate S5 locus encoding aspartic protease(Asp).Intragenic recombination within the Asp gene happened in a number of recombinants,resulting in chimeric S5j-S5n alleles.Just like S5n,the chimeric s5j-S5n allele displayed higher spikelet fertility when combined with the S5i allele.In the complementary test,however,the S5n allele from WCVs failed to enhance fertilities of the indica/japonica hybrids.Compared to both indica and japonica varieties.all nine WCVs from different resources are characterized with a 136 bp deletion in the Asp N-terminus.which probably renders the S5n allele non-functional.Furthermore,an A/C polymorphic site is detected 1,233 bp downstream of the Asp start codon.The heterozygous A/C site of the Asp gene in indica/japonica hybrid is believed to be the casual factorto causc partial sterility.The functional makers based on the two polymorphic sites will be broadly used in developing wide-compatibility rice varieties.     

杂交兰ChCAO基因的克隆及其在叶艺品系中的表达特征

【目的】叶绿素酸酯a加氧酶（CAO）是叶绿素b形成过程中的关键酶,为探究CAO基因在杂交兰叶艺形成中的调控作用,并为进一步研究杂交兰叶艺形成机理提供重要依据。【方法】该研究以杂交兰‘紫妍氏’（K21）及其叶艺品系‘中透紫妍氏’（K21-3）为试验材料,运用RT-PCR和RACE技术从叶片中克隆获得ChCAO基因;对ChCAO进行结构特征、理化性质、序列比对以及系统进化关系等分析;并利用qRT-PCR法对ChCAO在不同组织及叶艺品系叶片中的表达特性进行分析。【结果】结果表明,ChCAO基因编码区长1 608 bp,编码535个氨基酸,ChCAO与墨兰CAO亲缘关系最近,并与其他兰科植物CAO聚为一类。qRT-PCR结果显示,ChCAO基因表达具有组织特异性,在叶中相对表达量最高,根中相对表达量最低;此外,ChCAO在K21绿叶和K21-3绿叶区域叶片中的相对表达量显著高于K21-3叶艺区域叶片中的相对表达量。构建该基因的VIGS沉默载体转化烟草,发现沉默ChCAO后烟草叶片呈黄化状态,叶片中的叶绿素含量及ChCAO基因的相对表达量也显著降低,由此推测ChCAO基因的沉默表达可能导致叶绿素含量降低,叶片黄化,初步明确了杂交兰ChCAO基因的功能。     

Genetic analysis of a contact zone between two lineages of the ocellated lizard (Lacerta lepida Daudin 1802) in south‐eastern Iberia reveal a steep and narrow hybrid zone

Measuring the diffusion of genes between diverging taxa through zones of secondary contact is an essential step to understand the extent and nature of the reproductive isolation that has been achieved. Previous studies have shown that the ocellated lizard (Lacerta lepida Daudin, 1802) has endured repeated range fragmentation associated with the climatic oscillations of the Plio‐Pleistocene that promoted diversification of many different evolutionary units within the species. However, the oldest divergence within the group is estimated to have occurred much earlier, during the Miocene, around 9 Ma and corresponds to the split between the subspecies Lacerta lepida nevadensis Buchholz (1963) and Lacerta lepida lepida Daudin (1802). Although these two evolutionary units have documented genetic and morphological differentiation, most probably accumulated during periods of allopatry, little is known about patterns of gene flow between them. In this study, we performed a population genetic analysis of a putative area of secondary contact between these two taxa, using mtDNA and microsatellite data. We assessed levels of gene flow across the contact zone to clarify to what extent gene flow may be occurring. Hybridization between the subspecies was observed by the presence of genetically introgressed individuals. However, the overall coincidence of mitochondrial and multilocus nuclear clines and generally steep clines support the idea that this contact zone is acting as a barrier to gene flow. Taken together, these results suggest that L. l. lepida and L. l. nevadensis are in independent evolutionary trajectories and should be considered as two different species.     

Hybridization in headwater regions,and the role of rivers as drivers of speciation in Amazonian birds

Many understory birds and other groups form genetically differentiated subspecies or closely related species on opposite sides of major rivers of Amazonia, but are proposed to come into geographic contact in headwater regions where narrower river widths may present less of a dispersal barrier. Whether such forms hybridize in headwater regions is generally unknown, but has important implications to our understanding of the role of rivers as drivers of speciation. We used a dataset of several thousand single nucleotide polymorphisms to show that seven taxon pairs that differentiate across a major Amazonian river come into geographic contact and hybridize in headwater regions. All taxon pairs possessed hybrids with low numbers of loci in which alleles were inherited from both parental species, suggesting they are backcrossed with parentals, and indicating gene flow between parental populations. Ongoing gene flow challenges rivers as the sole cause of in situ speciation, but is compatible with the view that the wide river courses in the heart of Amazonia may have driven interfluvial divergence during episodes of wet forest retraction away from headwater regions. Taxa as old as 4 Ma in our Amazonian dataset continue to hybridize at contact zones, suggesting reproductive isolation evolves at a slow pace.     

Molecular characters and morphological genetics of CAL gene in Chinese cabbage

BepCAL,the homologous gene of CAL,was isolated from Chinese cabbage.Unlike BobCAL of cauliflower,BcpCAL did not hold the terninating mutation in the fifth exon.After crosses of cauliflower with Chinese cabbage,the resultant hybrids failed to form curd,which implicates the genetic complement of BcpCAL to the mutated BobCAL in the function of curd formation.One of CAL gene isolated from the hybrid apparently comes from the female parent(Chinese cabbage) even though there are a few of the bases substituted and deleted.The result offers the molecular and genetic evidences for the study of biological function of CAL in morphological genetics of curd.     

野败型杂交水稻恢复基因的AFLP标记研究

选择汕优６３Ｆ２的高可育株和高不育株分别建立２个基因池,利用ＡＦＬＰ标记技术对２池间的多态性进行了研究,分析表明,６４组引物在两池间全部扩增出了稳定,清晰的带纹,共计３４７７条带。多数引物在基因池间未呈现多态性,只有引物组合Ｅ－ＡＧＣ／Ｍ－ＣＡＡ在基因池间表现多态,用双亲、Ｆ１、Ｆ２单株以及生产和育种上的骨干不育系与恢复系验证均表明这组引物所揭示的多态性片段与恢复基因有关（命名为ＡＰ１）。ＡＰ１为     

Chromosomal assignment of porcine microsatellites by use of a somatic cell hybrid mapping panel

A well-established and characterized somatic cell hybrid panel was used to map three polymorphic microsatellites. Microsatellite S0072, representing the linkage group S0007-S0072, was assigned to porcine chromosome 14. Micro-satellite S0009, representing the unassigned linkage group EAM-S0009-S0071, was assigned tentatively to porcine chromosome 11. Finally, S0062 was tentatively mapped to chromosome 18. S0062 may represent the first marker for porcine chromosome 18.