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2012年  第33卷  第E5-6期

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Laurasiatheria is one of the richest and most diverse superorders of placental mammals. Because this group had a rapid evolutionary radiation, the phylogenetic relationships among the six orders of Laurasiatheria remain a subject of heated debate and several issues related to its phylogeny remain open. Reconstructing the true phylogenetic relationships of Laurasiatheria is a significant case study in evolutionary biology due to the diversity of this suborder and such research will have significant implications for biodiversity conservation. We review the higher-level (inter-ordinal) phylogenies of Laurasiatheria based on previous cytogenetic, morphological and molecular data, and discuss the controversies of its phylogenetic relationship. This review aims to outline future researches on Laurasiatheria phylogeny and adaptive evolution.
Gamma-aminobutyric acid (GABA) and glutamate are two important amino acid neurotransmitters widely present in the nervous systems of mammals, insects, round worm, and platyhelminths, while their receptors are quite diversified across different animal phyla. However, the evolutionary mechanisms between the two conserved neurotransmitters and their diversified receptors remain elusive, and antagonistic interactions between GABA and glutamate signal transduction systems, in particular, have begun to attract significant attention. In this review, we summarize the extant results on the origin and evolution of GABA and glutamate, as well as their receptors, and analyze possible evolutionary processes and phylogenetic relationships of various GABAs and glutamate receptors. We further discuss the evolutionary history of Excitatory/Neutral Amino Acid Transporter (EAAT), a transport protein, which plays an important role in the GABA-glutamate “yin and yang” balanced regulation. Finally, based on current advances, we propose several potential directions of future research.
Xenopus ZFP36L1 (zinc finger protein 36, C3H type-like 1) belongs to the ZFP36 family of RNA-binding proteins, which contains two characteristic tandem CCCH-type zinc-finger domains. The ZFP36 proteins can bind AU-rich elements in 3' untranslated regions of target mRNAs and promote their turnover. However, the expression and role of ZFP36 genes during neural development in Xenopus embryos remains largely unknown. The present study showed that Xenopus ZFP36L1 was expressed at the dorsal part of the forebrain, forebrain-midbrain boundary, and midbrain-hindbrain boundary from late neurula stages to tadpole stages of embryonic development. Overexpression of XZFP36L1 in Xenopus embryos inhibited neural induction and differentiation, leading to severe neural tube defects. The function of XZP36L1 requires both its zinc finger and C terminal domains, which also affect its subcellular localization. These results suggest that XZFP36L1 is likely involved in neural development in Xenopus and might play an important role in post-transcriptional regulation.
Though Yunnan province contains some 562 known species of fish, no cell lines from any of these have been made available to date. To protect germplasm resources and provide an effective tool in solving problems at cellular level of Anabarilius grahami, a fish endemic to Fuxian Lake, Yunnan, China, we established and characterized the major features of a continuous cell line (AGF II) from the caudal fin tissue of A. grahami. This AGF II cell line consists of fibroblast-like cells and has been subcultured more than 60 times over the course of a year. The cell line was maintained in DMEM/F12 supplemented with 10% FBS, with a cellular doubling time of 51.1 h. We continued with more experiments to optimize the culture and storage conditions, and found a variety of interesting results: cells could grow at temperature between 24 癈 and 28 癈, with the optimal temperature of 28 癈. Likewise, the growth rate of A. grahami fin cells increased when the FBS proportion increased from 5% to 20%, with the optimal growth at the concentrations of 20% FBS; cells were able to grow in L-15 and DMEM/F12 with optimal growth at L-15; DMSO is a better cryoprotectant than Glycerol, EG and MeOH for AGFII cells with optimal concentration of 5% DMSO. Chromosome analysis also showed that the distribution of chromosome number varies from 38 to 52, with a modal peak at 48 chromosomes, accounting for 39.8% of all cells. Using the same primer pairs specific to mtDNA, the AGF II cell sequences obtained by PCR were identical to those from muscle tissues of A. grahami. Both chromosome analysis and PCR amplification confirmed the AGF II cells were from A. grahami, also indicating that that current long-term artificial propagation of A. grahami has been successful. Finally, we noted that when cells were transfected with pEYFP-N1 and pECFP-N1 plasmid, bright fluorescent signals were observed, suggesting that this cell line may be suitable for use in transfection and future gene expression studies.
There are six micronuclear divisions during conjugation of Paramecium caudatum: three prezygotic and three postzygotic divisions. Four haploid nuclei are formed during the first two meiotic prezygotic divisions. Usually only one meiotic product is located in the paroral cone (PC) region at the completion of meiosis, which survives and divides mitotically to complete the third prezygotic division to yield a stationary and a migratory pronucleus. The remaining three located outside of the PC degenerate. The migratory pronuclei are then exchanged between two conjugants and fuse with the stationary pronuclei to form synkarya, which undergo three successive divisions (postzygotic divisions). However, little is known about the surviving mechanism of the PC nuclei. In the current study, stage-specific appearance of cytoplasmic microtubules (cMTs) was indicated during the third prezygotic division by immunofluorescence labeling with anti-alpha tubulin antibodies surrounding the surviving nuclei, including the PC nuclei and the two types of prospective pronuclei. This suggested that cMTs were involved in the formation of a physical barrier, whose function may relate to sequestering and protecting the surviving nuclei from the major cytoplasm, where degeneration of extra-meiotic products occurs, another important nuclear event during the third prezygotic division.
The genus Trachypithecus is the most diverse langur taxon, distributed in southwestern China, south and southeastern Asia. In this study, we include 16 recognized Trachypithecus species to reconstruct the phylogeny with particular concern to the taxonomy of the three subspecies of T. phayrei using multiple genes. Our results support a sister-relationship between T. p. phayrei and T. p. shanicus. However, the mitochondrial CYT B gene supported T. p. crepuscula as a distinct species, but the nuclear PRM1 gene suggested a closer relationship between T. p. crepuscula and T. p. phayrei. The incongruence between nuclear and mitochondrial genes suggests that hybridization may have occurred, a fact that would benefit from re-examination using multiple unlinked nuclear genes.
In the present study, we report the first complete mitochondrial genome (mitogenome) of the Painted Jezebel, Delias hyparete. The mitogenome of Delias hyparete is 15 186 bp in length, and has typical sets of 37 genes: 13 protein-coding genes (PCGs), 2 ribosomal RNAs, 22 transfer RNAs and a non-coding A+T-rich region. All protein-coding genes are initiated by ATN codons, except for COI, which is tentatively designated by the CGA codon, as observed in other butterfly species. A total of 10 PCGs harbored the complete termination codon TAA or TAG, while the COI, COII and ND5 genes ended at a single T residue. All 22 tRNA genes show typical clover structures, with the exception of the tRNASer(AGN) which lacks the dihydrouridine (DHU) stem and is instead replaced by a simple loop. Thirteen intergenic spacers totaling 153 bp, and 13 overlapping regions totaling 46 bp are scattered throughout the whole genome. The 377 bp long of D. hyparete A+T-rich region is not comprised of large repetitive sequences, but harbors several features characteristic of the lepidopteran insects, including the motif ATAGA followed by an 18 bp poly-T stretch, a microsatellite-like (AT)5 element preceded by the ATTTA motif, an 10 bp polyA-like stretch (AAAAATAAAA) present immediately upstream tRNAMet.
Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is increasingly being used for genome-wide profiling of transcriptional regulation, as this technique enables dissection of the gene regulatory networks. With input as control, a variety of statistical methods have been proposed for identifying the enriched regions in the genome, i.e., the transcriptional factor binding sites and chromatin modifications. However, when there are no controls, whether peak calling is still reliable awaits systematic evaluations. To address this question, we used a Bayesian framework approach to show the effectiveness of peak calling without controls (PCWC). Using several different types of ChIP-seq data, we demonstrated the relatively high accuracy of PCWC with less than a 5% false discovery rate (FDR). Compared with previously published methods, e.g., the model-based analysis of ChIP-seq (MACS), PCWC is reliable with lower FDR. Furthermore, to interpret the biological significance of the called peaks, in combination with microarray gene expression data, gene ontology annotation and subsequent motif discovery, our results indicate PCWC possesses a high efficiency. Additionally, using in silico data, only a small number of peaks were identified, suggesting the significantly low FDR for PCWC.