Structural and expressional analysis of a cDNA that expresses predominantly in rice stamens

The development of stamen is an important stage during the sexual reproduction in higher plants. Studying the genes that predominantly or even specifically expressed in stamens will aid in undestanding the molecular mechanism of stamen development. The structure of a rice CHS-like gene (D5) which predominantly expressed in anthers has been analysised, showing high structural similarity with two other anther-specific genes (A1 and BA42) fromBrassica napus. Northern analysis also reveals that the three genes share a similar expression pattern and that the expression of D5 may relate to the early development of pollens. It is concluded that D5, A1 and BA42 represent a group of diverged CHS-like genes which are related to stamen development.     

Roles of protein kinase C in oocyte meiotic maturation and fertilization

Protein kinase C (PKC) is a superfamily of Ser/Thr protein kinases that is distributed widely in eukaryotes. It plays key regulatory roles at multiple steps of oocyte meiotic maturation and fertilization. During the process of meiotic maturation, the activation of PKC in cumulus cells stimulates meiotic maturation, whereas the activation of PKC in oocytes results in the inhibition of germinal vesicle breakdown. PKC activity increases following the meiotic maturation, and decreases at the transition of metaphase/anaphase in meiosis I, so as to facilitate the release of the first polar body and the entry of meiosis II. In fertilization of mammalian oocytes, PKC may act as one of the downstream targets of Ca2+ to stimulate the cortical granule exocytosis, release the oocytes from MII arrest and to induce pronucleus formation. PKC is also involved in the regulation of maturation promoting factor (MPF) and mitogen-activated protein kinase (MAPK). Several PKC isoforms have been identified in mammalian oocytes, and there is evidence showing that classical PKCs may be the principal mediator of oocyte cortical reaction.     

黄牡丹花粉母细胞减数分裂过程的细胞遗传学观察

对黄牡丹花粉母细胞的减数分裂过程进行了全面的观察，发现在其减数分裂中存在诸如单价体、四价体、多价体、同源染色体联会不分离，后期Ⅰ～Ⅱ染色体桥及染色体断片、落后染色体、微核等一系列异常现象．统计了异常现象出现的频率；从细胞遗传学水平上分析了黄牡丹在野外结实率低与花粉母细胞减数分裂异常的关系．     

Function and interaction of maturation-promoting factor and mitogen-activated protein kinase during meiotic maturation and fertilization of oocyte

Mitogen-activated protein kinase (MAP kinase) cascade and maturation-promoting factor (MPF) play very important roles during meiotic maturation and fertilization of oocyte. Interaction between MAP kinase and MPF influences meiotic maturation and fertilization of oocyte throughout the animal kingdom, including stimulation of germinal vesicle breakdown (GVBD), suppression of DNA replication, control of meiotic chromosome segregation, maintenance of metaphase II arrest, and resumption and completion of second meiosis. This review focuses on the function and interaction of MAP kinase and MPF during meiotic maturation and fertilization of oocyte.     

Telomeres and meiosis in health and disease

Telomeres are important segments of chromosomes that protect chromosome ends from nucleolytic degradation and fusion. At meiosis telomeres display an unprecedented behavior which involves their attachment and motility along the nuclear envelope. The movements become restricted to a limited nuclear sector during the so-called bouquet stage, which is widely conserved among species. Recent observations suggest that telomere clustering involves actin and/or microtubules, and is altered in the presence of impaired recombinogenic and chromosome related functions. This review aims to provide an overview of what is currently known about meiotic telomere attachment, dynamics and regulation in synaptic meiosis.     

Telomeres and meiosis in health and disease

Telomeres are important segments of chromosomes that protect chromosome ends from nucleolytic degradation and fusion. At meiosis telomeres display an unprecedented behavior which involves their attachment and motility along the nuclear envelope. The movements become restricted to a limited nuclear sector during the so-called bouquet stage, which is widely conserved among species. Recent observations suggest that telomere clustering involves actin and/or microtubules, and is altered in the presence of impaired recombinogenic and chromosome related functions. This review aims to provide an overview of what is currently known about meiotic telomere attachment, dynamics and regulation in synaptic meiosis.     

褐家鼠染色体减数分裂联会复合体的研究

以界面铺张－硝酸银和磷钨酸（ＰＴＡ）染色技术，对褐家鼠（Ｒａｔｔｕｓｎｏｒｖｅｇｉｃｕｓ）减数分裂前期精母细胞联会复合体（ＳＣ）进行了显微和亚显微结构的观察．银染和ＰＴＡ染色都清楚地显示出褐家鼠ＳＣ的结构和减数分裂的行为，但ＰＴＡ染色的ＳＣ标本，着丝位区域较为明显．ＳＣｓ核型与有丝分裂染色体核型有较好的一致性．     

Abnormalities of meioses in male reciprocal hybrids between the Hiroshima and Ichinoseki populations ofRana japonica

In order to elucidate cytogenetically the cause of male sterility in intraspecific hybrids ofRana japonica, the behavior of chromosomes in the first meiosis was observed in spermatocytes from male reciprocal hybrids between two populations from Hiroshima and Ichinoseki. In the parental Hiroshima and Ichioseki populations, 2530 (96.7%) meiotic spreads had 13 bivalents and 78 (3.0%) contained 12 bivalents and two univalents, whereas in reciprocal hybrids only 337 (7.0%) contained 13 bivalents and the other 4445 (93.0%) had 2–26 univalents. A total of 31647 (93.4%) bivalents was ring-shaped and the other 2234 (6.6%) were rod-shaped in both parental populations, whereas in reciprocal hybrids 26352 (57.1%) and 19819 (42.9%) bivalents were ring- and rod-shaped, respectively. These results show that meiotic chromosomes of reciprocal hybrids are characterized by a remarkable increase in univalents and rod-shaped bivalents.     

蓬园100号锦橙少籽原因初探

蓬园100号锦橙品质好、种子少。细胞学观察染色体数目为2n=18。其少籽原因不是染色体数目异常,而是减数分裂中大量小孢子母细胞之间染色质穿壁导致遗传物质的分配不均和减数分裂异常,产生大量败育花粉粒所致。单核期是小孢子败育的主要时期。