The middle Miocene palynoflora and palaeoenvironments of Eskihisar (Yatağan basin,south‐western Anatolia): a combined LM and SEM investigation

We investigated a palynological section from middle Miocene sediments at Eskihisar (south‐western Anatolia) to establish biogeographic links of the palynoflora and to infer the palaeoenvironment. Four algal palynomorphs, nine spore taxa, eight gymnosperms, three monocots and 67 dicot pollen types were encountered and investigated using the ‘single grain method’ that combines light microscopy and scanning electron microscopy. Two pollen zones reflect different phases of basin development. Zonal vegetation remained fairly stable across the section and reflects heterogeneous environments including broad‐leaved deciduous forest, subtropical forest and sclerophyllous and semi‐evergreen oak forest. Conifers were accessory elements in the broad‐leaved deciduous forest communities and replaced these at higher elevations. Some herbaceous taxa (Plumbaginaceae) indicate scattered occurrences of sandy and/or rocky soils. Biogeographic affinities are general Northern Hemisphere, North American and East Asian, as also suggested by the macrofossil record. Only two taxa provide potential biogeographic links with the African flora. This suggests that biome shifts of plant taxa between African subtropical/tropical biomes and Anatolian (western Eurasian) temperate forests and shrublands may have been rare in the middle Miocene.     

Tyrosine phosphorylation as evidence of epididymal cauda participation in the sperm maturation process of Corynorhinus mexicanus bat

The bat Corynorhinus mexicanus provides an interesting experimental model for the study of epididymal sperm maturation because after spermatogenesis and the regression of the testes, this bat stores sperm in the epididymal cauda for several months. Earlier research conducted by our group suggested that sperm maturation in this species must be completed in the caudal region of the epididymis. One of the major signal transduction events during sperm maturation is the tyrosine phosphorylation of sperm proteins. The aim of the present study was to comparatively evaluate tyrosine phosphorylation in spermatozoa obtained from the caput, corpus and cauda of the epididymis during the sperm storage period. The maturation status of the sperm was determined by the percentage of capacitation and tyrosine phosphorylation in sperm obtained from the epididymis. The highest proportion of tyrosine phosphorylation was registered after the sperm had reached the cauda epididymis during the middle of the storage period. In conclusion, in Corynorhinus mexicanus and most likely in other chiropteran species with an asynchronous male reproductive pattern, epididymal sperm maturation ends in the caudal region of the epididymis and is related to the time that the sperm remains in the epididymis before mating activity.     

Young But Not Old Adult African Striped Mice Reduce Their Activity in the Dry Season When Food Availability is Low

An individual′s survival and fitness depend on its ability to effectively allocate its time between competing behaviors. Sex, social tactic, season and food availability are important factors influencing activity budgets. However, few field studies have tested their influences. The African striped mouse (Rhabdomys pumilio) lives in highly seasonal habitats in southern Africa, and individuals can adopt different social tactics. We investigated seasonal changes in activity budgets of different tactics and predicted that individuals will reduce their activity in the non‐breeding season to save energy when food availability is low and that young non‐breeding adults (‘philopatrics’) invest mainly in activities related to gaining body mass to increase survival probability. We predicted old adults (‘breeders’), which bred during the previous breeding season, to invest mainly in maintenance of their social status. We conducted 90 focal observations during the non‐breeding season and 73 during the breeding season. Activity budgets of striped mice were season and tactic specific, with philopatrics, but not breeders, reducing activity when food availability was low, possibly to decrease energy expenditure. Philopatrics of both sexes foraged and basked more in the breeding season than during the non‐breeding season. Male philopatrics gained body mass and female philopatrics maintained their body mass in both seasons. Sex‐specific differences occurred during the breeding season, when female breeders foraged more than male breeders, while male breeders chased other individuals more than female breeders. These findings indicate that individuals adopting different social tactics display distinct behaviors to fulfill tactic‐specific energetic needs .     

Bcl2l10, a new Tpx2 binding partner,is a master regulator of Aurora kinase A in mouse oocytes

Previously, we demonstrated that Bcl-2-like 10 (Bcl2l10) is associated with meiotic spindle assembly and that the gene that is most strongly down-regulated by Bcl2l10 RNAi is targeting protein for Xklp2 (Tpx2). Tpx2 is a well-known cofactor that controls the activity and localization of Aurora kinase A (Aurka) during mitotic spindle assembly. Therefore, this study was conducted (1) to identify the associations among Bcl2l10, Tpx2, and Aurka and (2) to understand how Bcl2l10 regulates meiotic spindle assembly in mouse oocytes. Bcl2l10, Tpx2, and Aurka co-localized on the meiotic spindles, and Bcl2l10 was present in the same complex with Tpx2. Tpx2 and Aurka expression decreased whereas phospho-Aurka increased in Bcl2l10 RNAi-treated oocytes. Counterbalancing changes in the levels of these 2 activators, Tpx2 and phospho-Aurka, resulted in decreased Aurka catalytic activity after Bcl2l10 RNAi treatment. Bcl2l10 RNAi decreased the expression of microtubule organizing center (MTOC)-related proteins, disturbed MTOC formation and disrupted meiotic spindle assembly. Our data demonstrate that Bcl2l10 is a binding partner of Tpx2 and a new regulator of the complex controlling the organization of microtubules and MTOC biogenesis in meiotic spindle assembly. The discovery of Bcl2l10 as a new effector of Aurka suggests that Bcl2l10 may have diverse functions in mitotic cells.     

The role of salinity in seed maturation of the euhalophyte Suaeda salsa

Controlled conditions were used to investigate how salinity maintains the salt tolerance of seeds and seedlings of the euhalophyte Suaeda salsa. Seeds were harvested from S. salsa plants that had been treated with 1 or 500 mM NaCl for 113 days in a glasshouse. The results showed that high salinity (500 mM NaCl) increased chlorophyll concentration and oxygen production in embryos of maturing seeds. At 500 mM NaCl, the phosphatidylglycerol and sulfoquinovosyldiacylglycerol levels and the digalactosyldiacylglycerol/monogalactosyldiacylglycerol ratio were higher in young seedlings derived from seeds whose source plants were cultured in 500 mM rather than in 1 mM NaCl. When seeds were incubated with 600 mM NaCl, the conductivity and malondialdehyde concentration in the embryos was greater if the source plants had been cultured in 1 mM rather than in 500 mM NaCl. The opposite pattern was evident for seedling survival and shoot weight. In conclusion, salinity during seed maturation may increase the salt tolerance of seeds and seedlings by increasing the oxygen production in the embryos of the maturing seeds and by changing the lipid composition of membranes in the seedlings.     

Overexpression of FAB1A-GFP recruits SNX2b on the endosome membrane in snx1–1 mutant in Arabidopsis

Phosphatidylinositol 3,5-bisphosphate [PI(3,5)P₂] is one of the phosphoinositides that controls endosomal trafficking events in eukaryotes. PtdIns(3,5)P₂ is produced from PI(3)P by phosphatidylinositol 3-phosphate 5-kinase FAB1/PIKfyve. Recently, we reported that FAB1 predominantly localizes on the SNX1-residing late endosomes and a loss-of FAB1 function causes the release of late endosomal effector proteins, ARA7/RABF2b and SORTING NEXIN 1 from the endosome membrane, indicating that FAB1 or its product PtdIns(3,5)P₂ mediates the maturation process of the late endosomes. Intriguingly, the ectopic expression of FAB1A could complement the sucrose-dependent seedling growth phenotype of snx1–1 mutant. Here, we demonstrated that the depletion of SNX1 causes the release of SNX2b-mRFP from the endosomal membrane. However, overexpression of FAB1A-GFP reassembles SNX2b-mRFP on the endosomal membrane despite the absence of SNX1. From these results, we proposed that SNX2b homodimer or SNX2a/SNX2b heterodimer might function as functional Sorting Nexin complex instead of SNX1 to attach the endosomal membrane by binding of overproduced PI(3,5)P₂ in Arabidopsis.     

长春蒲公英雄性不育株形态学观察与败育细胞学研究

在长春蒲公英(Taraxacum junpeianum Kitam.)株群中发现雄性不育现象,为研究其败育机理及特点,探寻其不育基因,采用形态观察法、石蜡切片技术和染色体压片法,对长春蒲公英野生型及其雄性不育株的花药发育过程和花粉母细胞减数分裂过程进行了观察。结果表明:(1)长春蒲公英雄性不育株花药中部发红、干瘪、无花粉散出。与野生型比较,雄性不育株雄蕊更短,子房更窄,种子形态更加狭长;(2)长春蒲公英雄性不育株败育时期为四分体到单核小孢子前期,败育方式为小孢子自身异常发育,绒毡层异常分解,互相粘连败育;(3)长春蒲公英雄性不育株花粉母细胞减数分裂二分体时期出现落后微核,随后产生极少四分体,并且四分体产生大量染色体桥,小孢子营养物质流失,彻底败育。因此,长春蒲公英雄性不育株败育彻底、稳定,并且有种的特点。小孢子自身异常发育和绒毡层异常分解是导致败育的主要原因。     

厚朴基原植物及其4个近缘种的花粉鉴定

采用扫描电镜对2种厚朴基原植物(厚朴Magnolia officinalis Rehd.et Wils.、凹叶厚朴M.officinalis Rehd.et Wils.var.biloba Rehd.et Wils.)及4种近缘植物(玉兰M.denudata Desr.、紫玉兰M.liliiflora Desr.、望春玉兰M.biondii Pampan.、荷花玉兰M.grandiflora L.)的花粉形态、表面纹饰和大小进行了观察研究。结果显示:(1)6种植物的花粉粒均为单粒,具远极单萌发沟,沟长,直达两端,左右对称,异极;侧面观均为舟形,两端较尖,赤道面观为椭圆形或近椭圆形,极面观均为近圆形;外壁均具小穴状或网状纹饰。(2)厚朴的小穴状纹饰小而浅,不明显;凹叶厚朴的小穴状纹饰小但较深,也不甚明显;相比之下,紫玉兰、玉兰、望春玉兰和荷花玉兰的花粉粒表面密布不规则隆起及深穴点,明显。(3)6种植物花粉粒由大至小依次为:荷花玉兰凹叶厚朴厚朴玉兰紫玉兰望春玉兰。3种不同的花粉处理方法中,自然干燥法能清晰地观察到花粉的扫描电镜特征,此方法优于戊二醛固定法和叔丁醇真空冷冻干燥法。本研究结果为厚朴中药资源的基原植物及其近缘种鉴定提供了新的证据,也为现代植物从种及亚种级水平分类提供了参考。     

Developmental capacity of mouse oocytes that undergo maturation in vitro: Effect of the hormonal state of the oocyte donor

In a previous study, it was shown that cumulus cell-enclosed germinal vesicle (GV)-stage oocytes, isolated from pregnant mares' serum gonadotropin (PMSG)-primed immature (22–24 day old) mice and that underwent spontaneous maturation in vitro, exhibited frequencies of embryonic development similar to oocytes stimulated to mature and ovulate in vivo by administration of gonadotropins [Schroeder AC, Eppig JJ, (1984) Dev Biol 102:493–497]. In the present study, the effect of the hormonal state of the oocyte donor on the capacity of in vitro matured oocytes to be fertilized and undergo pre- and post-implantation development was explored further. Oocytes were isolated at the GV-stage from the following groups of mice: 1) unprimed immature mice; 2) adult cycling mice; 3) unprimed Snell dwarf (dw) mice that have undetectable levels of growth hormone (GH), prolactin, and thyroid-stimulating hormone (TSH); and 4) primed and unprimed hypogonadal (hpg) mice that have undetectable levels of circulating gonadotropins. Oocytes maturing in vitro after isolation from normal unprimed immature or adult mice at all stages of the estrous cycle acquired full developmental capacity. GV-stage oocytes isolated from dwarf mice showed embryonic development equivalent to normal ( + /?) littermate controls. Therefore, GH, TSH, or prolactin are not required during oogencsis in vivo to promote the acquisition of competence to complete embryogenesis after maturation in vitro. Oocytes from hypogonadal mice had a much reduced capacity for preimplantation development when compared with normal littermates. Administration of PMSG to the hypogonadal mice significantly increased the developmental capacity of oocytes that underwent maturation in vitro. Gonadotropins, therefore, have a beneficial effect on the oocytc's capacity for embryonic development.     

Heat-shock proteins during pollen development in maize

In contrast to sporophytic tissues, mature pollen of higher plants does not synthesize the typical set of heat-shock proteins (HSPs) in response to a marked temperature upshift. Immature grains, however, seem able to do so, at least partially. We investigated the characteristics of HSP synthesis throughout the male gametophytic phase in maize and compared gametophytic and sporophytic heat-shock responses. One-dimensional Sodium dodecyl sulfate-polyacryl-amide gel electrophoresis technique (SDS-PAGE) of newly synthesized proteins revealed that immature pollen synthesizes HSPs, some of which are not induced in sporophytic tissues. The heat-shock response appeared to be related to microgametophytic developmental stages. The strongest response was found in uninucleate microspores: at this stage, in addition to the sporophytic 102, 84, 72, and 18 kD HSPs, three other polypeptides of 74, 56, and 46 kD were observed. In the binucleate and trinucleate stages, only a reduced synthesis of few HSPs could be induced, and differences between genotypes were observed. In germinating pollen, HSP synthesis was not induced under a voriety of heat-stress conditions; however, the consti-tutive synthesis of two polypeptides of the same molecular weight, 72 and 64 kD, as two HSPs was observed. The biological significance of these results is discussed.