EVOLUTIONARILY STABLE SIZE OF A MEGAGAMETOPHYTE: EVOLUTION OF TINY MEGAGAMETOPHYTES OF ANGIOSPERMS FROM LARGE ONES OF GYMNOSPERMS

To examine the factors favoring large megagametophytes of gymnosperms and tiny ones of angiosperms, a game model for seed production was developed in which megagametophytes growing in the same female parent compete for resources provided by the parent. In the model, megagametophytes may continue to grow until seed completion or may cease to grow at a certain time and regrow at pollination or fertilization. Autonomous abortion of unpollinated or unfertilized megagametophytes may occur either at pollination or fertilization. Those megagametophytes absorb a certain amount of resources before abortion, due to constraints in the signal process, in addition to the resources absorbed before pollination or fertilization. It was found that both growth habits can be the ESS: megagametophytes continue to grow without cessation and monopolize resources, such as gymnosperms, or cease to grow until fertilization to reduce the loss of resources due to autonomous abortion, such as angiosperms. The former and the latter are the ESS if the time interval between pollination and fertilization is long and short, respectively. Thus, the fertilization interval may be a critical factor selecting for large megagametophytes of gymnosperms or tiny ones of angiosperms.     

低能钒离子注入花生种子的深度分布

采用鼎瑟福背散射（RBS）和X射线能谱分析法（EDAX）对V元素在花生种子中的深度分布进行了测量,并用扫描电镜对注入前后花生种胚的形貌变化进行观察。结果表明,由于样品表面较粗糙以及其特殊结构,RBS方法不适于测量钒在花生肿胚中的深度分布,trim95也不适合于对注入钒离子在花生种子中的深度进行模拟,而EDAX的测量结果表明V离子的穿透深度可达到15μm。另外,注入前后花生种胚的形貌发生了显著变化。     

Comparison of NAA and 2,4-D induced somatic embryogenesis in Cassava

NAA and 2,4-D were compared for their ability to induce somatic embryogenesis in cassava (Manihot esculenta Crantz). In all seven cultivars tested, only 2,4-D had the capacity to induce primary somatic embryos from leaf explants, however, both NAA and 2,4-D were capable of inducing secondary somatic embryos. More secondary somatic embryos were formed in NAA than in 2,4-D medium. Furthermore, the maturation period for secondary somatic embryos was shorter in NAA medium than in 2,4-D medium. In some cultivars, repeated subculture of secondary somatic embryos in NAA medium resulted in a gradual shift from somatic embryogenesis to adventitious root formation. This shift could be stopped and reversed by subculture of the material in 2,4-D medium. In NAA medium the most secondary somatic embryos were formed when they were subcultured every 15 days whereas in 2,4-D a 20 day subculture interval was optimal. Subculture of secondary somatic embryos at a high inoculum density (>1.5 g jar⁻¹) in NAA medium did not result in the formation of secondary somatic embryos, whereas in 2,4-D it lead to the formation of globular secondary somatic embryos. With 2,4-D the newly induced secondary somatic embryos were connected vertically to the explant and with NAA medium horizontally. For all cultivars tested, desiccation stimulated normal germination of NAA-induced somatic embryos. However, the desiccated, secondary somatic embryos required a medium supplemented with BA for high frequency germination. The concentration of BA needed for high frequency germination was higher when the desiccated secondary somatic embryos were cultured in light instead of dark. In only one cultivar desiccation enhanced germination of 2,4-D induced secondary somatic embryos and in three other cultivars it stimulated only root formation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Xist敲降可以改善孤雄单倍体囊胚质量

单倍体胚胎干细胞研究一直以来吸引着研究者们的注意,它可以用作基因修饰的工具或是用于药物筛选。随着孤雄胚胎干细胞系的成功建立,更扩展了单倍体胚胎干细胞的应用前景。但单倍体孤雄胚胎发育率低,胚胎质量差,制约着孤雄单倍体胚胎干细胞的建系。为改善孤雄单倍体胚胎发育潜能及胚胎干细胞建系效率低的问题,我们检测了小鼠(Mus musculus domesticus)孤雄单倍体胚胎的体外发育过程和该过程中Xist基因表达情况。结果发现,孤雄单倍体胚胎囊胚发育率只有10%~14%,发育至囊胚所需时间差异较大,从3.5~5.5 d不等。通过核糖核酸荧光原位杂交实验(RNA-FISH)跟踪Xist基因表达情况,发现其在发育至囊胚阶段的胚胎中呈抑制状态,而在早期胚胎中多呈表达状态。通过si RNA扰低Xist表达,虽然没有改变孤雄单倍体胚胎发育到囊胚的比例,但显著提高了囊胚质量,并提高了接种胚胎内细胞团(ICM)后建立细胞系的效率。结果说明,Xist基因的表达可能是导致小鼠孤雄单倍体胚胎质量差、干细胞建系率低的原因之一。     

苹果渣乙醇提取物抗菌活性及防腐作用研究

为提高苹果渣资源利用率,探究苹果渣乙醇提取物的抗菌活性和防腐性能,该文采用微波辅助提取法制取苹果渣乙醇提取物,用抑菌圈实验测定其抗菌活性,并研究了其防腐作用.结果表明:(1)苹果渣乙醇提取物对酵母菌抑制作用不明显(抑菌圈直径<1 mm),对金黄色葡萄球菌和大肠杆菌的抑菌作用较明显(抑菌圈直径为6～9 mm),最佳抑菌浓...     

Factors affecting the dormancy and germination of bleeding heart [Lamprocapnos spectabilis (L.) Fukuhara] seeds

• Information on the optimal conditions to promote the germination of Lamprocapnos spectabilis (L.) Fukuhara seeds is limited; consequently, this study was conducted to establish the requirements to break seed dormancy and promote germination.
• The selected seeds had morphophysiological dormancy and had not begun embryo development. To study the dormancy breaking and embryo development processes, seeds were subjected to constant or changing temperature treatments during moist stratification.
• High temperature and humidity resulted in vigorous embryo growth, with the longest embryos occurring after 1 month of incubation at 20 °C. At 4 °C, the seeds required incubation period of at least 3 months to germinate. Embryo growth and germination were higher with changing high and low temperatures than under a constant temperature, and changing temperatures also considerably changed the endogenous hormone levels, embryo development and germination. Bioactive gibberellin (GA) content was higher in seeds incubated at 20 °C for 1 month, then at 4 °C for 2 months. The content of endogenous abscisic acid in seeds subjected to the same treatment decreased by 97.6% compared with that of the untreated seeds.
• Embryo growth and seed germination require changing high and low temperatures; however, exogenous GA₃ could substitute for high temperatures, as it also causes accelerated germination. In this study, the seeds of L. spectabilis were identified as an intermediate simple type, a sub‐level of morphophysiologically dormant seeds.

     

秦巴山区野生百合(Lilium spp.)的育种应用研究

为探索秦巴山区野生百合资源在百合育种中的应用方向及途径, 获得具有其独特遗传背景的育种材料,将秦巴山区野生百合的抗病毒及独特观赏特性等优良遗传性状逐渐渗到栽培品种中去。该研究借助切割柱头杂交及胚抢救技术,选取6种秦巴山区野生百合［岷江百合(Lilium gegale)、宜昌百合(L. leucanthum)、山丹（L. pumilum）、野百合（L. brownii）、宝兴百合（L. duchartrei）、川百合（L. davidii）］以及亚洲百合（Asiatic hybrids,AA）品种‘Elite’、东方百合（Oriental hybrids,OO）品种‘Sorbonne’、‘Siberia’和‘Marlon’、OT百合（Oriental × Trumpet hybrids,OT）品种‘Yelloween’、‘Serano’、‘Corel′door’进行了32组共计263朵花的（品）种间杂交,并针对膨大变软的果实剥离可供离体培养的胚及胚囊进行胚抢救。结果表明：（1）不同杂交组合坐果率、胚获得及萌发率呈现出较大差异,综合坐果率为11.4%,对30个膨大的果实中共计38个可供离体培养的胚及胚囊进行胚抢救,有7株最终萌发。（2）以野生百合为父母本的12组杂交组合中,6组获得了膨大果实,得到6株杂交后代。（3）栽培百合做母本,野生百合做父本的20组杂交组合中,共9组获得了膨大果实,除‘Elite’ × 山丹可直接收获种子外,共得到1株杂交后代。（4）以岷江百合及宜昌百合为亲本的远缘杂交TT × AA及回交OT × TT成功获得杂种后代。（5）秦巴山区6种野生百合在远缘杂交中获得育种后代的几率存在较大差异,宜昌百合和岷江百合获得后代几率较高,宝兴百合获得后代几率较低,野百合未获得后代。以上结果表明,岷江百合和宜昌百合为母本的TT × AA杂交和宝兴百合为父本的TT × AA杂交以及岷江百合和宜昌百合为父本的OT回交,为三种百合的育种利用提供了新途径,野百合的育种应用途径需要继续探索。     

Altered sperm tsRNAs in aged male contribute to anxiety‐like behavior in offspring

Parental age at first pregnancy is increasing worldwide. The offspring of aged father has been associated with higher risk of several neuropsychiatric disorders, such as schizophrenia and autism, but the underlying mechanism remains elusive. Here we report that advanced paternal age in mice alters the profile of transfer RNA‐derived small RNAs (tsRNAs). Injection of sperm tsRNAs from aged male mice into zygotes induced anxiety‐like behaviors in F1 males. RNA sequencing of the cerebral cortex and hippocampus of those F1 male mice altered the gene expression of dopaminergic synapse and neurotrophin. tsRNAs from aged male mice injection also altered the neuropsychiatry‐related gene expression in two‐cell and blastocyst stage embryos. More importantly, the sperm tsRNA profile changes significantly during aging in human. The up‐regulated sperm tsRNA target genes were involved in neurogenesis and nervous system development. These results suggest that aging‐related changes of sperm tsRNA may contribute to the intergenerational transmission of behavioral traits.