Development of Tapet urn and Microspores in Canna L.: an Example of an Invasive but Non-syncytial Tapetum

An investigation of microsporogenesis in Canna L. revealed thatthe tapetum is invasive but non-plasmodial. Tapetal cell protoplastsare released as individuals. In the loculus they are at firstmore or less spherical but can produce amoeboid processes inlate stages of microsporogenesis. They do not fuse with oneanother. Meiosis is normal and cytokinesis is successive. Theimplications of the novel type of tapetum are discussed. canna, Canna, invasive non-syncytial tapetum, tapetum, microsporogenesis     

Alterations and Abnormal Mitosis of Wheat Chromosomes Induced by Wheat-Rye Monosomic Addition Lines

Background

Wheat-rye addition lines are an old topic. However, the alterations and abnormal mitotic behaviours of wheat chromosomes caused by wheat-rye monosomic addition lines are seldom reported.

Methodology/Principal Findings

Octoploid triticale was derived from common wheat T. aestivum L. ‘Mianyang11’×rye S. cereale L. ‘Kustro’ and some progeny were obtained by the controlled backcrossing of triticale with ‘Mianyang11’ followed by self-fertilization. Genomic in situ hybridization (GISH) using rye genomic DNA and fluorescence in situ hybridization (FISH) using repetitive sequences pAs1 and pSc119.2 as probes were used to analyze the mitotic chromosomes of these progeny. Strong pSc119.2 FISH signals could be observed at the telomeric regions of 3DS arms in ‘Mianyang11’. However, the pSc119.2 FISH signals were disappeared from the selfed progeny of 4R monosomic addition line and the changed 3D chromosomes could be transmitted to next generation stably. In one of the selfed progeny of 7R monosomic addition line, one 2D chromosome was broken and three 4A chromosomes were observed. In the selfed progeny of 6R monosomic addition line, structural variation and abnormal mitotic behaviour of 3D chromosome were detected. Additionally, 1A and 4B chromosomes were eliminated from some of the progeny of 6R monosomic addition line.

Conclusions/Significance

These results indicated that single rye chromosome added to wheat might cause alterations and abnormal mitotic behaviours of wheat chromosomes and it is possible that the stress caused by single alien chromosome might be one of the factors that induced karyotype alteration of wheat.     

用抑制差减杂交法分离小麦幼苗水分胁迫诱导表达的cDNA

小麦种子水培 ,幼苗长至一叶一心后 ,在 2 0℃生长箱中水培 4 8h作为对照组 (Driver) ,PEG 6 0 0 0水溶液胁迫培养 4 8h作为处理组 (Tester)。进行抑制差减杂交 ,构建包含 15 0 0个独立克隆的SSH文库。以正向和反向差减杂交后的cDNA为探针 ,筛选SSH文库 ,得到 181个阳性克隆 ,测序后获不重复EST 10 1个。     

Abnormal Sporogenesis in Wheat (Triticum aestivum L.) Induced by Short Periods of High Temperature

Plants of Triticum aestivum L. cv. Gabo, grown at 20 °C,were exposed to 30 °C for short periods during the timebetween the beginning of meiosis in the pollen mother cellsand anthesis. Plant water deficit at this temperature was avoidedby maintaining a high atmospheric relative humidity and tissuewater potential did not change. This temperature treatment appliedfor 3 days, at the time of reduction division and tetrad breakup in the male tissue, lowered grain yield through a drasticreduction in grain set, but was without effect at other stagesof development. Grain set was also reduced by exposing plantsto 30 °C for 1 day only or to a 30 °C day, 20 °Cnight (16 h photoperiod) regime for 3 days during the sensitiveperiod. A reduction in grain set did not result in a compensatoryincrease in the weight of remaining grains. The female fertility of previously heat-stressed plants wasassessed by pollinating with pollen from plants grown at a lowertemperature (20 °C). Grain set in such plants was less thanthat in plants grown at the lower temperature and hand pollinatedwith similar pollen, indicating that female fertility was reducedby high temperature. This was not the sole reason for reducedgrain set, however, as some anthers on heat-stressed plantswere small and neither extruded nor dehisced normally. Suchanthers contained pollen grains that were mostly shrivelled,had abnormal cytoplasm and showed no reaction to 2, 3, 5-triphenyltetrazolium chloride. Similar effects were also noted in pollenfrom apparently normal anthers on heat-stressed plants. Triticum aestivum, wheat, heat stress, pollen, sporogenesis, grain set, male sterility, female sterility     

Development of the Tapetum in Pinus banksiana Preceding Sporogenesis

Early in sporangial ontogeny, the cells destined to become thesporogenous and tapetal tissue differentiate in a strikinglysimilar manner. The first conspicuous step in development isa contraction of the protoplasts, beginning at the centre ofthe microsporangium and moving radially to its periphery. Similardevelopment of the two groups of cells ceases as the callosewall is formed around the meiocytes. At this point the originalwalls investing the tapetal cells become gelatinous, and lipidsynthesis commences within the contracted protoplasts. The bulkof this lipid is secreted from the cells, and becomes lodgedin the loculus, either as globules in the expanded radial andinner cell walls, or as a continuous layer on the inside ofthe middle lamella separating the loculus from the wall of themicrosporangium. This lipoidal layer forms the basement of aperitapetal membrane, believed to serve as a container for thefluid in which the young sporogenous cells are immersed. Examination of protein levels and ribosome numbers in the tapetalcells reveals that protein synthesis proceeds at an increasingrate throughout the development preceding meiosis, but apparentlyceases as the pollen mother cells become enveloped in callose.     

利用荧光原位杂交技术检测导入普通小麦的大赖草染色质

利用以大赖草基因组ＤＮＡ为探针的荧光原位杂交技术对导入普通小麦的大赖草染色质进行检测。结果：９１）根尖体中花粉母细胞时期均可用于检测大赖草染色质。间期核中杂交信号点数与所含大赖草染色体数目之间的对应关系依染色体显强Ｃ－带末端数不同而不同;（２）利用荧光原位杂交,从普通小麦－大赖草单体异附加系的减数分裂前植株＾６０Ｃｏ－γ射线辐射后代中检测到一批大赖草端着丝粒染色体和小麦－大赖草染色体易位等结构变异     

Analysis of Differential Proteins Induced by Forchlorfenuron in Wheat

To identify differential proteins induced by N-(2-chloro-4-pyridy)-N??-phenylurea or forchlorfenuron (CPPU), two-dimensional electrophoresis was used to study the variations in protein expression of wheat seedlings induced with CPPU. The expressed protein spots were identified by matrix-assisted laser desorption/ionization?Ctime of flight mass spectrometry and protein data bank query. About 800 spots were reproducibly detected in three replicates of each sample. A total of 10 differential proteins were identified, including tRNA delta (2)-isopentenylpyrophosphate transferase (S1), probable peptide ABC transporter ATP-binding protein y4tS (S2), ribosomal RNA large subunit methyltransferase N (S3), microtubule-associated protein 6 (S4), actin-66 (Fragment) (S5), mitochondrial ATP synthase subunit alpha (S6), S-adenosylmethionine synthase 1 (S7), flavin-containing monooxygenase YUCCA4 (S8), GTPase obg (S9), and ribosomal RNA small subunit methyltransferase G (S10). These proteins were closely related to phytohormone synthesis, plant stress response, energy metabolism, protein synthesis, cytoskeleton, and transport. All of these processes may play important roles in wheat seedling development. These findings could provide valuable information for the further study of the functions and underlying mechanism of the action of CPPU. Thus, proteomic analysis revealed that CPPU treatment induces variations in many proteins involved in plant growth and development.     

Immune Focusing and Enhanced Neutralization Induced by HIV-1 gp140 Chemical Cross-Linking

Experimental vaccine antigens based upon the HIV-1 envelope glycoproteins (Env) have failed to induce neutralizing antibodies (NAbs) against the majority of circulating viral strains as a result of antibody evasion mechanisms, including amino acid variability and conformational instability. A potential vaccine design strategy is to stabilize Env, thereby focusing antibody responses on constitutively exposed, conserved surfaces, such as the CD4 binding site (CD4bs). Here, we show that a largely trimeric form of soluble Env can be stably cross-linked with glutaraldehyde (GLA) without global modification of antigenicity. Cross-linking largely conserved binding of all potent broadly neutralizing antibodies (bNAbs) tested, including CD4bs-specific VRC01 and HJ16, but reduced binding of several non- or weakly neutralizing antibodies and soluble CD4 (sCD4). Adjuvanted administration of cross-linked or unmodified gp140 to rabbits generated indistinguishable total gp140-specific serum IgG binding titers. However, sera from animals receiving cross-linked gp140 showed significantly increased CD4bs-specific antibody binding compared to animals receiving unmodified gp140. Moreover, peptide mapping of sera from animals receiving cross-linked gp140 revealed increased binding to gp120 C1 and V1V2 regions. Finally, neutralization titers were significantly elevated in sera from animals receiving cross-linked gp140 rather than unmodified gp140. We conclude that cross-linking favors antigen stability, imparts antigenic modifications that selectively refocus antibody specificity and improves induction of NAbs, and might be a useful strategy for future vaccine design.     

Perfect Absorption of Light by Coherently Induced Plasmon Hybridization in Ultrathin Metamaterial Film

We demonstrated numerically that light can be totally absorbed by an ultrathin metamaterial film through coherently induced plasmon hybridization. Two fundamental modes, namely symmetrical and antisymmetrical modes, are observed in the metal–insulator–metal structure and attributed to the electric and magnetic resonance, respectively. Each kind of resonance is related to a distinct absorption peak for the corresponding coherent inputs. In particular, it is found that the antisymmetrical absorption is almost omnidirectional and suitable for divergent beams with arbitrary polarization and angle of incidence. To interpret the interaction of magnetic and electric fields with the structure, effective material parameters of the metamaterial are also retrieved, showing good agreement with the intuitive discussion. Furthermore, the general condition of coherent perfect absorption in a metamaterial thin film is given, which could be helpful for the design and understanding of such absorbers.     

濒危植物红花木莲小孢子发生及雄配子体发育的研究

首次报道了木莲属胚胎学特性,研究了红花木莲Manglietia insignis(Wall.)Bl.的小孢子发生、雄配子体的发育以及花粉萌发情况,红花木莲花药具有４个小孢子囊。花药壁５－６层,腺质绒毡层具有２－层细胞,小孢减数分裂后胞质分裂为修性同时型;四个分体排列方式为交叉型或左右对称型,偶为直线型;成熟花粉为二细胞型花粉粒,同时报道了化粉木莲在小孢子发生过程中的特有的现象,花粉萌发率为１４．７％－２５．３％。联系红花木莲花粉粒数目和胚珠数目进行探讨,认为雄配子体发育不是影响红花木莲结籽率低的主要因素。     

Identification by Suppression Subtractive Hybridization of Frankia Genes Induced under Nitrogen-Fixing Conditions

Frankia is an actinobacterium that fixes nitrogen under both symbiotic and free-living conditions. We identified genes upregulated in free-living nitrogen-fixing cells by using suppression subtractive hybridization. They included genes with predicted functions related to nitrogen fixation, as well as with unknown function. Their upregulation was a novel finding in Frankia.Frankia is a Gram-positive actinobacterium that establishes symbiosis with several angiosperms termed actinorhizal plants and forms nitrogen-fixing nodules on their roots (20). Frankia also fixes nitrogen in free-living culture under nitrogen-free conditions (19). Induction of the nitrogen-fixing ability is accompanied by differentiation of vesicles (19). Vesicles are spherical cells specialized to nitrogen fixation and are surrounded by multilayered lipid envelopes by which nitrogenase is protected from oxygen (3). Frankia plays an important role in the global nitrogen cycle, yet little is known about the genes involved in the induction of nitrogen-fixing activity. Recently, three Frankia genome sequences were determined (15), which facilitates the genetic dissection of Frankia biology. In this study, we identified Frankia genes induced in nitrogen-fixing cells under free-living conditions by using suppression subtractive hybridization (SSH) (4).     

ST273是拟南芥绒毡层和小孢子发育的必需基因

绒毡层在拟南芥花药花粉发育过程中具有重要作用,包括分泌降解胼胝质的胼胝质酶、为花粉壁的形成提供原料以及为小孢子发育提供营养物质.本文通过对拟南芥雄性不育突变体st273的分析,研究了ST273基因在花药花粉发育过程中的功能.st273是通过T-DNA插入诱变野生型拟南芥得到的一株突变体,遗传分析表明st273是单隐性核基因控制的.利用图位克隆的方法对不育基因ST273进行了定位,结果表明ST273基因与拟南芥第三条染色体上分子标记CIW11连锁.生物信息学分析发现该分子标记附近有一个调控花粉发育的基因TDF1.测序分析结果表明在st273突变体中,TDF1基因第三个外显子上459位的碱基发生了由G459变成了A459的单碱基变化,导致ST273基因该位点提前终止突变.等位分析结果表明st273与tdf1是等位突变体.st273突变体营养生长期发育正常,但生殖生长发育出现异常.亚历山大染色结果显示st273突变体花药中没有花粉.组织切片观察结果表明,突变体花药绒毡层异常肥大且空泡化,四分体不能正常释放小孢子,最终无法形成花粉.这些结果揭示了ST273蛋白质参与调控了绒毡层和小孢子发育过程.     

渗透胁迫诱导的小麦叶片细胞程序性死亡

用20%PEG6000（-0.63MPa）溶液对小麦（Triticumaestivum）根系进行渗透胁迫,在DNA琼脂糖凝胶电泳图谱上观察到明显的梯状DNA条带,表明PEG处理诱发了DNA核小体间的断裂,从而表现出典型的细胞程序性死亡的生化特征;末端脱氧核糖核酸转移酶介导的3′-OH末端标记法（terminal deoxynucleotidyl transferase(TdT)-mediated dUTP nick end     

用RAPD和染色体原位杂交检测Elymus rectisetus染色体附加到普通小麦中

报道小麦×Elymusrectisetus属间杂种BC2F236个衍生系,通过染色体原位杂交和RAPD分析,检测Elymusrectisetus染色体及其特异染色体DNA标记。原位杂交结果表明,36个衍生系中大多数系含1对异源Erectisetus染色体,少数系含3条以上Ereclisetus染色体;RAPD结果表明,有13个随机引物（OPBA-08、OPB－14OPEA-09、OPF-05、OPF－09、OPJ-05、OPK-03、OPN-12、OPP-20、OPS－12、OPT-20、OPZ-09、OPZ-11）能够在这36个衍生系中分别扩增出普通小麦所没有的Erectisetus特异的染色体DNA片段。其中Erectisetus特异染色体DNA片段OPF－05480bp、OPF－09650bp和OPZ-11350bp只能够在“1048”系统的全部8个株系中扩增出;OPN-12350bp只能够在“1057”系统的全部6个株系中扩增出;OPB-14900bp和OPM-05420bp只能够在“1034”、“1026”2个系统的全部22个株系和“1057”－5－3株系中扩增出。直接获得了3个类型不同的异附加系,省去常规通过测配和附加系两两杂交F1PMCMI细胞学鉴定来确证异附加系之间的异同。由此说明染色体原位杂交和RAPD分析有机结合是鉴定异附加系（异代换系）快速有效的方法,且方法简单、易行．     

宁夏枸杞异型绒毡层发育的超微结构特点

采用半薄和超薄切片技术对宁夏枸杞(Lycium barbarum L.)异型绒毡层的来源、结构及发育特点进行了研究,结果表明:(1)枸杞异型绒毡层由药隔绒毡层和药壁绒毡层组成,两种绒毡层除了来源、形态及分布位置不同外,其分化、成熟和降解时间,以及细胞质组成、分泌物成分等均有差异.(2)小孢子母细胞期间,药隔绒毡层细胞电子密度大,具有很强的脂质性质,光滑内质网和脂质小泡很丰富;而药壁绒毡层细胞中的核糖体和粗糙内质网较多.四分体后期,两种绒毡层细胞均含有很丰富的核糖体、粗糙内质网和分泌团.减数分裂前,两种绒毡层的细胞壁出现松散并呈絮状.之后,由于不同发育时期绒毡层细胞的不同分泌物在絮状细胞壁中的分布,致使二者的细胞壁都出现了一系列变化.(3)从小孢子早期开始,两种绒毡层细胞的质膜都发生了局部解体.分析推测,在母细胞期间药隔绒毡层具有较高的糖和脂类合成率,药壁绒毡层具有较高的蛋白质类合成率;在四分体后期,药隔绒毡层具有加强胼胝质酶合成和分泌的功能;而两种绒毡层絮状松散的细胞壁和局部解体的质膜有利于绒毡层的较大颗粒分泌物大量、顺利地分泌出绒毡层细胞.     

抑制消减杂交法分离紫花苜蓿幼苗铝胁迫诱导表达的cDNA

利用抑制消减杂交(SSH)技术分离铝胁迫诱导紫花苜蓿差异表达的基因,以水培试验获取的中苜一号幼苗为材料,以80μmol/L铝离子胁迫的紫花苜蓿作为试验组,未胁迫的为驱动组,构建了一个包含456个克隆的SSH文库。对构建的文库进行鉴定,随机选取20个阳性克隆测序,共获得15条有效EST序列,然后将测序结果提交到GenBank进行Blastn比对,获得了3条未知基因的序列,推测它们可能与植物的抗铝作用有关。检测结果表明,构建的文库质量较好,可以进行进一步深入研究,为揭示植物耐铝性的分子机理提供理论基础。