云南松雄配子在人工培养和自然条件下的发生

云南松(Pinus yunnanensis Fr.)花粉于三月在四细胞时期散粉。花粉在珠心顶端萌发,然后花粉管进入珠心组织,管核进入花粉管。第二年三月,休眠的花粉管在珠心内恢复活动,四月形成二个不等的雄配子。在雄配子周围有一些淀粉粒分布。花粉孵育在含蔗糖的培养基中生长要比在BKBM-WS培养基中缓慢。花粉粒及花粉管中含有大量直径4—8微米的淀粉粒,在不含蔗糖的培养基中,淀粉粒积累较少,直径约2—5微米。培养在2—5℃低温下的花粉可以缓慢地萌发,但不能形成雄配子。花粉管的伸出以及外壁的裂开总是发生在远极端薄壁区,花粉管可产生2—5条分枝或向两侧平行地生长,在萌发的早期,花粉粒以及花粉管中的细胞质十分稠密,蛋白质含量丰富。管核的蛋白质染色反应最深,生殖核次之。当生殖细胞分裂形成不育细胞及精原细胞后,管核染色反应稍有下降,花粉管中细胞质集中在顶端区域。当精原细胞分裂形成二精子时,花粉管中细胞质仅分布在二个精细胞及不育细胞和管核四周,其余部分已很少或缺乏。     

Patterns and mechanisms in instances of endosymbiont‐induced parthenogenesis

Female‐producing parthenogenesis can be induced by endosymbionts that increase their transmission by manipulating host reproduction. Our literature survey indicates that such endosymbiont‐induced parthenogenesis is known or suspected in 124 host species from seven different arthropod taxa, with Wolbachia as the most frequent endosymbiont (in 56–75% of host species). Most host species (81%, 100 out of 124) are characterized by haplo‐diploid sex determination, but a strong ascertainment bias likely underestimates the frequency of endosymbiont‐induced parthenogenesis in hosts with other sex determination systems. In at least one taxon, hymenopterans, endosymbionts are a significant driver of transitions from sexual to parthenogenetic reproduction, with one‐third of lineages being parthenogenetic as a consequence of endosymbiont infection. Endosymbiont‐induced parthenogenesis appears to facilitate the maintenance of reproductive polymorphism: at least 50% of species comprise both sexual (uninfected) and parthenogenetic (infected) strains. These strains feature distribution differences similar to the ones documented for lineages with genetically determined parthenogenesis, with endosymbiont‐induced parthenogens occurring at higher latitudes than their sexual relatives. Finally, although gamete duplication is often considered as the main mechanism for endosymbiont‐induced parthenogenesis, it underlies parthenogenesis in only half of the host species studied thus far. We point out caveats in the methods used to test for endosymbiont‐induced parthenogenesis and suggest specific approaches that allow for firm conclusions about the involvement of endosymbionts in the origin of parthenogenesis.     

我国被子植物体外受精研究—十年回顾

简要回顾了十余年来我国被子植物体外受精领域的研究历程和主要成就。我国科学家在性细胞的分离 ,尤其是生活胚囊和雌配子的分离方面走在国际前列。在一定程度上我国科学家的开拓性工作引起了国际同行的广泛兴趣和重视 ,推动了该领域的迅速发展 ,为实现被子植物真正意义的体外受精做出了独特的贡献。十年来 ,我国已建立了自己独特的被子植物离体受精实验技术系统并利用该系统与国际同行合作进行了一系列研究 ,尤其在探讨配子相互作用、卵细胞激活、避免多精入卵的机制等方面做出了创新性工作 ,为正确认识体外受精系统的优越性与局限性 ,也为深入探讨受精机制提供了有价值的新资料。目前正以体外受精操作系统结合细胞生物学和分子生物学等多种手段对受精过程中的一些重要事态与机理做进一步探讨     

VE161小麦外源染色体的传递特点

VE161小麦包括具有一对长穗偃麦草染色体的雄性不育代换系,可育附加系和杂育系,杂育系由其代换系×附加系产生,其外源染色体（E染色体）具有促进小麦部分同源染色体配对作用。本报道了VE161小麦本身含E染色体配子的传递率为VE161小麦与普通小麦杂交F2,BC1中分离出含E染色体植株的频率,发现VE161小麦本身含E染色体配子的传递率极高,而在F2和BC1代分离群体中保留或消除E染色体都较为容易,这一特点极利于E染色体促进部分同源染色体配对作用在创造易位系上的应用。     

热激蛋白在昆虫生殖中的功能及作用机制

热激蛋白(Hsp)在生殖过程中有着至关重要的作用。近年来,Hsp在昆虫生殖相关功能与机制研究方面取得了重要进展。基于此,本文主要就Hsp在昆虫精子发生和精子保护、卵成熟和卵子保护、生殖应答以及衰老进化机制等方面的研究进展进行了综述,旨在为进一步深入研究Hsp与昆虫生殖的关系提供参考,并为害虫防治和益虫利用提供新思路。     

Gamete discharge by Bryopsis plumosa (Codiales, Chlorophyta) induced by blue and UV-A light

Gamete discharge by the coenocytic green alga Bryopsis plumosa (Hudson) C. Agardh is induced by light. The mature male gametangia consist of a mass of quiescent male gametes and a large central vacuole. Within a few minutes after the onset of irradiation, breakdown of the tonoplast of the central vacuole and initiation of gamete motility occur simultaneously. This is followed by a forced discharge of moving gametes through a hole ruptured at the subapical region of the gametangium. The action spectrum for the light-induced gamete discharge was determined from a series of fluence-response curves. This action spectrum, having two major maxima at 370 and 450 nm, indicates the involvement of a blue light/UV-A-absorbing photoreceptor previously described as ‘cryptochrome’.     

Sperm cells in pollen tubes ofNicotians tabacum L.: three-dimensional reconstruction,cytoplasmic diminution,and quantitative cytology

Summary The organization of the sperm cells and vegetative nucleus (male germ unit) ofNicotiana tabacum was examined 18 h after semivivo pollination using transmission electron microscopy, computerassisted serial section reconstruction and quantitative cytology. Based on a measurement of 11 cellular parameters in nine reconstructed sperm cell pairs, there are no statistically significant differences between the two cells. The S_vn is characterized by a strapshaped cytoplasmic extension that is physically associated with the surface of the vegetative nucleus. The nucleus is located adjacent to the sperm crosswall, with sperm organelles being distributed between the nucleus and the extension. The S_ua is a tapered cell with cytoplasmic areas at both poles and deep axial invaginations near the crosswall. This cell has a centrally-located nucleus and a largely polar distribution of organelles. Three mechanisms for cytoplasmic diminution were observed that appear to contribute actively to the loss of cytoplasmic volume and organelles: (1) enucleated cytoplasmic body production in the S_ua; (2) vesiculation at the tip of the cytoplasmic projection of the S_vn; and (3) vesicle-containing body accumulation in the periplasm of both the S_vn and S_ua.Abbreviations 3-D three-dimensional - ECB enucleated cytoplasmic body - MGU male germ unit - S_vn leading sperm cell - S_ua trailing sperm cell - TEM transmission electron microscopy - VCB vesicle-containing body     

Detection of acrosome-reacted toad sperm based on specific lectin binding to the inner acrosomal membrane

When the sperm of the toad Bufo japonicus were treated with fluorescein isothiocyanate (FITC)-conjugated peanut agglutinin (PNA), soybean agglutinin (SBA), or Dolichos biflorus agglutinin (DBA), a few sperm fluoresced at the acrosomal region. The number of sperm showing this lectin binding to the acrosome increased significantly upon mild sonication of the sperm suspension. Electron microscopy revealed that ferritin-conjugated PNA bind not to the outer acrosomal and overlying plasma membranes, but specifically to the surface of the inner acrosomal membrane exposed by sonication. Both the percentage of FITC-PNA-labeled sperm and the activity of vitelline coat lysin released by sperm increased in good correlation with increasing sonication time, although the PNA-labeled sperm decreased in number upon longer sonication. These results indicate that the binding of FITC-PNA to the sperm provides a reliable measure of the acrosome reaction of Bufo sperm.     

Scanning electron microscope study of in vitro prepenetration gamete interactions

Hamster and mouse capacitated spermatozoa were interacted in vitro with hamster and mouse eggs in homologous and heterologous combinations. Also, fertilized and trypsin treated unfertilized hamster eggs, and unfertilized rat eggs were made to interact with capacitated hamster spermatozoa. The surface of the zona pellucida was then examined with the scanning electron microscope. It was found that sperm attachment, followed by sperm binding and penetration through the zona pellucida, was observed only when homologous gamete combinations were used. Binding of the spermatozoa to the zona was evidenced by the lytic effect of the acrosomal enzymes on the zona substance. When fertilized eggs and trypsin-treated unfertilized hamster eggs were mixed with capacitated hamster spermatozoa as well as in the heterologous gamete combinations, we found that the spermatozoa were able to establish attachment but not binding. Under these conditions the outer surface of the zona pellucida was never found to have penetration tracks made by the spermatozoa. Failure of heterologous spermatozoa to cross the foreign zona pellucida is believed to be associated with the inability of the foreign spermatozoa to establish binding and to the inability of their acrosomal enzymes to digest the zona. A similar mechanism is believed to work in zona-reacted and in trypsin-treated hamster eggs inseminated in vitro with homologous spermatozoa.     

Synchronization of encystment of <Emphasis Type="BoldItalic">Scrippsiella lachrymosa</Emphasis> (Dinophyta)

The encystment of Scrippsiella lachrymosa cells (strain B-10), which can be induced reliably in encystment medium, was inhibited by stirring the culture. 100 mL cultures in glass beakers were stirred at 1 rotation s⁻¹. Stirring inhibited vegetative cells from congregating (swarming) at the walls of the culture container. When stirring was stopped, a rapid induction of sexual reproduction was seen. As soon as stirring stopped (within 2 min), cells were observed swarming near the edges of the glass beaker. Four days after cessation of stirring, large percentages of the cells were mating and, after 7 days, most were zygotes. Cultures were observed after 31, 38, and, 45 days of stirring. When cultures were stirred for 45 days, cysts developed in the stirred treatments, but these cysts were attached to flocculent material that had also formed in the medium. The use of this laboratory method is advantageous for the study of the mating through cyst stages of the dinoflagellate life history. This method may also demonstrate the need for a ‘surface’ as a place for the dinoflagellate to congregate in order to successfully encyst and may help explain environmental observations of encystment at pycnoclines.