Contrasting genetic variation and differentiation on Hainan Island and the Chinese mainland populations of Dacrycarpus imbricatus (Podocarpaceae)

Dacrycarpus imbricatus is a vulnerable conifer in China whose geographical distribution encompasses large island but small mainland populations, providing a framework for contrasting the patterns of population genetic composition. In this study, seven populations on Hainan Island and the Chinese mainland were sampled throughout its distribution range and assessed using ISSR. The results did not show significant differences neither in genetic variation nor in genetic differentiation between the island and the mainland populations (P > 0.05). Severe bottlenecks were identified at population, island/mainland as well as range-wide scales. A relatively high level of variation but a low degree of differentiation was revealed. Ecological and life traits were suggested to play main roles in the shaping of genetic variation pattern. Of them long generation times could have exerted a lagging effect on both the genetic variation and differentiation. Our findings may contribute to establish management practices.     

A comparative analysis of genetic diversity in medicinal Chrysanthemum morifolium based on morphology, ISSR and SRAP markers

The diversity and genetic relationship among 29 populations of Chrysanthemum morifolium, one of Chrysanthemum indicum and one of Chrysanthemum nankingense from China were analyzed using morphological traits and molecular markers. Twenty morphological traits were scored as well as 182 ISSR marker-fragments, as amplified by 22 primers [the percentage of polymorphic bands (PPB): 81.87%], and 243 SRAP marker-fragments as generated by 26 primer pairs (PPB: 75.72%). Mantel’s test indicated significant correlation (r = 0.624) of morphological trait and SRAP. By contrast, the morphological trait showed low correlation with ISSR (r = 0.246). Cluster analysis showed groupings of the accessions according to all four methods correlated well with their geographic region of origin, and most populations from the south of China were classified into one cluster and most populations from the north of China were classified into another cluster. Finally, an appropriate strategy for conserving the C. morifolium germplasm was proposed.     

CXCR6/CXCL16 functions as a regulator in metastasis and progression of cancer

Metastasis is considered the obvious mark for most aggressive cancers. However, little is known about the molecular mechanism of the regulation of cancer metastasis. Recent evidence increasingly suggests that the interaction between chemokines and chemokine receptors is pivotal in the process of metastasis. The chemokine receptor CXCR4 and its ligand CXCL12, for example, have been reported to play a vital role in cancer metastasis. Another chemokine and chemokine receptor pair, the CXCL16/CXCR6 axis, has been studied by several independent research groups. Here, we summarize recent advances in our knowledge of the function of CXC chemokine receptor CXCR6 and its ligand CXCL16 in regulating metastasis and invasion of cancer. CXCR6 and CXCL16 are up-regulated in multiple cancer tissue types and cancer cell lines relative to normal tissues and cell lines. In addition, both CXCR6 and CXCL16 levels increase as tumor malignancy increases. Trans-membranous CXCL16 chemokine reduces proliferation while soluble CXCL16 chemokine enhances proliferation and migration. TM-CXCL16 functions as an inducer for lymphocyte build-up around tumor sites. High trans-membranous CXCL16 expression correlates with a good prognosis. Moreover, the Akt/mTOR signal pathway is involved in activating the CXCR6/CXCL16 axis. These findings suggest multiple opportunities for blocking the CXCR6/CXCL16 axis and the Akt/mTOR signal pathway in novel cancer therapies.     

Fast evolution of the retroprocessed mitochondrial rps3 gene in Conifer II and further evidence for the phylogeny of gymnosperms

The popular view that plant mitochondrial genome evolves slowly in sequence has been recently challenged by the extraordinarily high substitution rates of mtDNA documented mainly from several angiosperm genera, but high substitution rate acceleration accompanied with great length variation has been very rarely reported in plant mitochondrial genes. Here, we studied evolution of the mitochondrial rps3 gene that encodes the ribosomal small subunit protein 3 and found a dramatically high variation in both length and sequence of an exon region of it in Conifer II. A sequence comparison between cDNA and genomic DNA showed that there are no RNA editing sites in the Conifer II rps3 gene. Southern blotting analyses of the total DNA and mtDNA, together with the real-time PCR analysis, showed that rps3 exists as a single mitochondrial locus in gymnosperms. It is very likely that the Conifer II rps3 gene has experienced retroprocessing, i.e., the re-integration of its cDNA into the mitochondrial genome, followed by an evolutionary acceleration due to the intron loss. In addition, the phylogenetic analysis of rps3 supports the sister relationship between conifers and Gnetales. In particular, the monophyly of conifer II is strongly supported by the shared loss of two rps3 introns. Our results also indicate that the mitochondrial gene tree would be affected in topology when the “edited” paralogs are analyzed together with their genomic sequences.     

Functional analysis of the inhibitor of apoptosis genes in <Emphasis Type="Italic">Antheraea pernyi</Emphasis> nucleopolyhedrovirus

The inhibitor of apoptosis proteins (IAP) plays an important role in cell apoptosis. We cloned two novel IAP family members, Ap-iap1 and Ap-iap2, from Antheraea pernyi nucleopolyhedrovirus (ApNPV) genome. Ap-IAP1 contains two baculoviral IAP repeat (BIR) domains followed by a RING domain, but Ap-IAP2 has only one BIR domain and RING. The result of transient expression in Spodoptera frugiperda (Sf21) showed that Ap-iap1 blocked cell apoptosis induced by actinomycin D treatment and also rescued the p35 deficient Autographa californica nucleopolyhedrovirus (AcNPV) to replicate in Sf9 cells, while Ap-iap2 does not have this function. Several Ap-IAP1 truncations were constructed to test the activity of BIRs or RING motif to inhibit cell apoptosis. The results indicated that BIRs or RING of Ap-IAP1 had equally function to inhibit cell apoptosis. Therefore deletion of above both of the above domains could not block apoptosis induced by actinomycin D or rescue the replication of AcMNPVΔp35. We also screened two phage-display peptides that might interact with Ap-IAP1.     

Development of Juglans Regia SSR Markers by Data Mining of the EST Database

Walnut (Juglans regia), an economically important woody plant, is widely cultivated in temperate regions for its timber and nutritional fruits. Despite abundant studies in germplasm, systemic molecular evaluations of walnut are sparsely reported mainly due to the limited molecular markers available. Expressed sequence tags (EST) provide a valuable resource for developing simple sequence repeat (SSR) markers. In this study, a total of 5,025 walnut ESTs (covering 16.41 Mb) were retrieved from the National Center for Biotechnology Information database. The SSR motifs were then analyzed by the SSRHunter software. In total, 398 SSRs were obtained with an average frequency of 1/4.08 kb. Dinucleotide (di-) repeat motifs accounted for 69.85% of all SSRs, followed by trinucleotide (tri-) with a frequency of 27.64%, while low frequency (2.51%) of tetranucleotide (tetra-) to hexanucleotide (hexa-) was observed. Meanwhile, GCA and TC motifs were prevalent among di- and tri- loci, respectively. Subsequently, a total of 123 primer pairs were designed from the non-redundant SSR-containing unigenes with the selection threshold of SSR length set to 10 bp or more. To examine the efficiency of candidate markers, seven DNA pools were collected from geographically different accessions. Results demonstrated that 41 SSR primer sets could generate high polymorphic amplification products (33.3%), and these polymorphic loci were mainly located in the 3′-untranslated region. Annotation analysis revealed that only two of these 41 loci were located inside open reading frames of characterized proteins (E ≤ 1E−30).     

Differences between karyotypically normal and abnormal human embryonic stem cells

Objectives: To compare different biological characteristics of human embryonic stem cells (HESCs) between those with normal and those with abnormal karyotype. Materials and methods: Culture‐adapted HESCs (chHES‐3) with abnormal karyotype were compared with karyotypically normal cells, with regard to pluripotency and differentiation capacity, ultrastructure, growth characteristics, gene expression profiles and signalling pathways. Results: We found a new abnormal karyotype of HESCs. We observed that chHES‐3 cells with normal and abnormal karyotypes shared similarities in expression markers of pluripotency; however, karyotypically abnormal chHES‐3 cells had a tendency for differentiation towards ectoderm lineages and were easily maintained in suboptimal culturing conditions. Abnormal chHES‐3 cells displayed relatively mature cell organelles compared to normal cells, and karyotypically abnormal chHES‐3 cells had increased survival and population growth. Genes related to cell proliferation and apoptosis were up‐regulated, but genes associated with genetic instability (p53, Rb, BRCA1) were down‐regulated in the karyotypically abnormal cells. Conclusion: Karyotypically abnormal chHES‐3 cells had a more developed capacity for proliferation, resistance to apoptosis and less genetic stability compared to normal chHES‐3 cells and may be an excellent model for studying and characterizing initial stages that determine transition of embryonic stem cells into cancer stem cells.