水稻ＣＭＳ—ＷＡ育性恢复基因的定位

在由227个组合组成的珍汕97A×（珍汕97B×密阳46）F     

Lipid modulation of ion channels through specific binding sites

Ion channel conformational changes within the lipid membrane are a key requirement to control ion passage. Thus, it seems reasonable to assume that lipid composition should modulate ion channel function. There is increasing evidence that this implicates not just an indirect consequence of the lipid influence on the physical properties of the membrane, but also specific binding of selected lipids to certain protein domains. The result is that channel function and its consequences on excitability, contractility, intracellular signaling or any other process mediated by such channel proteins, could be subjected to modulation by membrane lipids. From this it follows that development, age, diet or diseases that alter lipid composition should also have an influence on those cellular properties. The wealth of data on the non-annular lipid binding sites in potassium channel from Streptomyces lividans (KcsA) makes this protein a good model to study the modulation of ion channel structure and function by lipids. The fact that this protein is able to assemble into clusters through the same non-annular sites, resulting in large changes in channel activity, makes these sites even more interesting as a potential target to develop lead compounds able to disrupt such interactions and hopefully, to modulate ion channel function. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.     

多胺对水稻CMS系及其保持系幼穗蛋白质、核酸和活性氧代谢的影响

用ＤＡｒｇ＋ ＭＧＢＧ 处理保持系, 降低花粉可育度, 并使其幼穗中蛋白质、ＤＮＡ 和ＲＮＡ含量以及蛋白酶、ＲＮＡ 酶和ＤＮＡ 酶活性下降,使Ｏ－·２ 生成速率和ＭＤＡ 含量上升。Ｐｕｔ＋ Ｓｐｄ ＋ Ｓｐｍ 可消除或部分消除ＤＡｒｇ ＋ＭＧＢＧ的上述效应（ 对酶活性的影响除外） 。ＤＡｒｇ ＋ ＭＧＢＧ 也使ＰＯＤ、ＳＯＤ 和ＣＡＴ活性上升, 但是,多胺只能降低抑制剂对ＰＯＤ 的刺激作用。用Ｐｕｔ＋ Ｓｐｄ ＋ Ｓｐｍ 处理不育系, 使花粉可育度轻度提高, 并使其幼穗蛋白质、ＤＮＡ和ＲＮＡ 含量略有上升,使蛋白酶、ＤＮＡ酶和ＲＮＡ 酶活性、Ｏ－·２ 生成速率、ＭＤＡ 含量、ＳＯＤ 和ＣＡＴ活性下降, 使ＰＯＤ 活性上升     

Design, synthesis, expression, and characterization of the genes for mouse Fc gamma RIIb1 and Fc gamma RIIb2 cytoplasmic regions.

The cytoplasmic regions of the mouse low-affinity Fc gamma RII isoforms, mFc gamma RIIb1, and mFc gamma RIIb2, play a key role in signal transduction by mediating different cellular functions. mFc gamma RIIb1 has a 94-residue cytoplasmic region, whereas mFc gamma RIIb2 has a 47-residue cytoplasmic region. Genes encoding the cytoplasmic regions of mFc gamma RIIb1 (b1-94) and mFc gamma RIIb2 (b2-47) were designed, synthesized, and expressed as fusion proteins in Escherichia coli. A sequence-specific protease, thrombin, was used to release the b1-94 peptide, which was purified by using HPLC. The b2-47 peptide was synthesized chemically. CD spectropolarimetry was employed to examine the secondary structures of b1-94 and b2-47. These studies were conducted in aqueous solution, in mixtures of water and trifluoroethanol or methanol, and as a function of temperature. The results indicate that the b1-94 and b2-47 structures are sensitive functions of the solvent environment, and that nonaqueous solvents induce significant alpha-helical structure.     

Hemagglutinin of Influenza Virus Partitions into the Nonraft Domain of Model Membranes

The HA of influenza virus is a paradigm for a transmembrane protein thought to be associated with membrane-rafts, liquid-ordered like nanodomains of the plasma membrane enriched in cholesterol, glycosphingolipids, and saturated phospholipids. Due to their submicron size in cells, rafts can not be visualized directly and raft-association of HA was hitherto analyzed by indirect methods. In this study, we have used GUVs and GPMVs, showing liquid disordered and liquid ordered domains, to directly visualize partition of HA by fluorescence microscopy. We show that HA is exclusively (GUVs) or predominantly (GPMVs) present in the liquid disordered domain, regardless of whether authentic HA or domains containing its raft targeting signals were reconstituted into model membranes. The preferential partition of HA into ld domains and the difference between lo partition in GUV and GPMV are discussed with respect to differences in packaging of lipids in membranes of model systems and living cells suggesting that physical properties of lipid domains in biological membranes are tightly regulated by protein-lipid interactions.     

洋葱花粉母细胞中胞间连丝和胞质通道内的胞质骨架

用DGD包埋去包埋方法,观察了洋葱花粉母细胞中胞间连丝和胞质通道内的胞质骨架分布。结果发现,在花粉母细胞的胞间连丝内有胞质骨加分布,这些骨架纤维集结成束,穿过胞间连丝。在胞质通道内也有胞质骨架分布,但与胸间连丝内的骨困分布有所不同,主要表现为两种形式;骨架纤维致密或稀少。研究讨论了胞质骨架在胞间连丝和胞质通道内的作用。     

Cybrids and tetrad sterility for developing true potato seed hybrids

Potato cybrids result from the fusion between cytoplasm and nuclear gene donors. Such genetic materials are an alternative means to broaden the breeding pool by non‐sexual gene transfer. Tetrad pollen sterility provides also another source of male sterility with some potential for true potato seed breeding. The objective of this research was to investigate cybrid‐derived offspring for both agronomic and reproductive characteristics in two contrasting Peruvian locations, and to examine new exotic germplasm for tetrad sterility, with the aim of broadening the breeding pool available at the Centro Internacional de la Papa (CIP). The cybrids were derived from fusions between Y‐245.7, a clone with tetrad sterility, and Atzimba. These cybrids were crossed with selected male parents from the CIP breeding population, and their hybrid offspring were tested in La Molina (coastal desert) and Huancayo (cool highlands). In addition, other clones with tetrad sterility were also crossed with selected testers to determine their breeding value. There were significant differences for tuber yield, style length, and berry number among the hybrid offspring, and the genotype by environment interaction was significant for tuber yield and berry number. The top 25% highest yielding cybrid‐derived offspring across both locations showed the same tuber yield although they were significantly different for some of the reproductive characteristics. With the exception of one cybrid, the others did not exhibit segregation for tetrad sterility in their hybrid offspring, which were male fertile. However, the offspring derived from crosses between other sources of tetrad sterility and the same testers all showed tetrad sterility, and some of them had outstanding tuber yield at La Molina. The lack of segregation for tetrad sterility in these new crosses suggests that the non‐cybrid, male sterile, female parents are triplex or quadriplex for the Tr nuclear locus, which interacts with a sensitive cytoplasm (e.g. Trs from S. verrucosum or S. stoloniferum) to produce tetrad sterility in potato.     

Unilateral and bilateral hybridization barriers in inter-series crosses of 4x 2EBN Solanum stoloniferum, S. pinnatisectum, S. cardiophyllum, and 2x 2EBN S. tuberosum haploids and haploid-species hybrids

Wild Mexican potato species are an important untapped source of useful variation for potato improvement. Introgression methods such as 2n gametes, chromosome doubling, and crossing with disomic 4x 2 endosperm balance number (EBN) bridge species have been used to overcome post-zygotic endosperm failure according to the EBN hypothesis. Stylar barriers can prevent zygote formation, bilaterally when zygote formation is blocked in both directions of the cross or unilaterally when zygote formation is blocked in self incompatible (SI) × self compatible (SC) crosses. In several Solanaceae species, the S-locus for SI has been implicated in interspecific incompatibility. The objectives of this research were to determine if: (1) disomic 4x 2EBN Solanum stoloniferum can be used as a bridge species for introgression of the Mexican 2x 1EBN species Solanum cardiophyllum and Solanum pinnatisectum, (2) pre- and/or post-zygotic barriers limit hybridization among EBN compatible Solanum inter-series crosses, and (3) reproductive barriers act unilaterally or bilaterally. Fruit formation and seed set was recorded for inter-pollinations of S. stoloniferum, 4x 2EBN chromosome doubled S. cardiophyllum and S. pinnatisectum, and 2x 2EBN S. tuberosum haploids (HAP) or haploid-species hybrids (H-S). In vivo pollen tube growth was analyzed for each cross combination with fluorescence microscopy. Attempts to create bridge hybrids between S. stoloniferum, and S. cardiophyllum or S. pinnatisectum were not successful. Pre- and post-zygotic barriers prevented seed formation in crosses involving S. cardiophyllum and S. pinnatisectum. Self compatibility in S. stoloniferum and S. pinnatisectum suggests that the S-locus does not contribute to the stylar barriers observed with these species. Alternatively, the presence of functional and nonfunctional (SC) S-alleles may explain interspecific incompatibility in intra- and inter-ploidy crosses. A non-stylar unilateral incongruity was discovered in H-S/HAP × S. stoloniferum crosses, indicating either a post-zygotic barrier, or a pre-zygotic barrier acting at or within the ovary. Furthermore, lack of S. stoloniferum pollen rejection may occur through absence of S. stoloniferum pollen-active genes needed to initiate pollen rejection, or through competitive interaction in S-locus heterozygous S. stoloniferum pollen. Introgression strategies using these species would benefit potato breeding by introducing genetic diversity for several traits simultaneously through co-current introgression.     

The transmission and effects of Wolbachia bacteria in parasitoids

Wolbachia bacteria are obligatory intracellular parasites of arthropods and have been detected in about 70 species of parasitic wasps and three parasitoid flies. Wolbachia are transmitted cytoplasmically (maternally) and modify host reproduction in different ways to enhance their own transmission: parthenogenesis induction (PI), cytoplasmic incompatibility (CI), or feminization (F) of genetic males. Only PI and CI are known in parasitoids. PI-Wolbachia cause thelytoky in otherwise arrhenotokous parasitoids by generating diploid (rather than haploid) unfertilized wasp eggs. CI-Wolbachia cause incompatibility of crosses between infected males and uninfected females because the paternally derived chromosomes fail to decondense and are destroyed after syngamy. More complex situations arise when hosts harbor multiple infections, which can lead to bidirectional incompatibility and may be involved in parasitoid speciation. The relative fitness of infected and uninfected hosts is important to the population dynamics of Wolbachia, and more data are needed. Evolutionary conflict should be common between host genes, Wolbachia genes, and other "selfish" genetic elements. Wolbachia-specific PCR primers are now available for several genes with different rates of evolution. These primers will permit rapid screening in future studies of spatial and temporal patterns of single and multiple infection. Molecular phylogenies show that CI- and PI-Wolbachia do not form discrete clades. In combination with experimental transfection data, this result suggests that host reproductive alterations depend on the interaction between attributes of both Wolbachia and host. Moreover, Wolbachia isolates from closely related hosts do not usually cluster together, and phylogenies suggest that Wolbachia may have radiated after their arthropod hosts. Both results support considerable horizontal transmission of Wolbachia between host species over evolutionary time. Natural horizontal transmisson between parasitoids and their hosts, or with entomoparasitic nematodes or ectoparasitic mites, remains a tantalizing but equivocal possibility. Received: November 27, 1998 / Accepted: January 15, 1999