The protein import pore Tom40 in the microsporidian Nosema bombycis

Microsporidia, an unusual group of unicellular parasites related to fungi, possess a highly reduced mitochondrion known as the mitosome. Since mitosomes lack an organellar genome, their proteins must be translated in the cytosol before being imported into the mitosome via translocases. We have identified a Tom40 gene (NbTom40), the main component of the translocase of the outer mitochondrial membrane, in the genome of the microsporidian Nosema bombycis. NbTom40 is reduced in size, but it is predicted to form a β-barrel structure composed of 19 β-strands. Phylogenetic analysis confirms that NbTom40 forms a clade with Tom40 sequences from other species, distinct from a related clade of voltage-dependent anion channels (VDACs). The NbTom40 contains a β-signal motif that the polar residue is substituted by glycine. Furthermore, we show that expression of NbTom40, as a GFP fusion protein within yeast cells, directs GFP to mitochondria of yeast. These findings suggest that NbTom40 may serve as an import channel of the microsporidian mitosome and facilitate protein translocation into this organelle.     

湖南宏门冲溪鱼类多样性研究初报

2002年9～10月,我院生物系对湖南省通道县国家阔叶林采种基地宏门冲溪鱼类多样性进行了初步研究,共采集到标本鱼10种,分属于2目5科9属。通过对其多样性分析,结果表明：宏门冲鱼类多样性复杂,群落结构稳定。     

Experiencing winter for spring flowering: A molecular epigenetic perspective on vernalization

Many over-wintering plants, through vernalization, overcome a block to flowering and thus acquire competence to flower in the following spring after experiencing prolonged cold exposure or winter cold. The vernalization pathways in different angiosperm lineages appear to have convergently evolved to adapt to temperate climates. Molecular and epigenetic mechanisms for vernalization regulation have been well studied in the crucifer model plant Arabidopsis thaliana.Here, we review recent progresses on the vernalization pathway in Arabidopsis. In addition, we summarize current molecular and genetic understandings of vernalization regulation in temperate grasses including wheat and Brachypodium, two monocots from Pooideae, followed by a brief discussion on divergence of the vernalization pathways between Brassicaceae and Pooideae.     

Selective cytotoxicity of scFv-TNF fusion protein on the tumor cells

A fusion protein of single-chain, Fv-tumor necrosis factor , scFv-TNF, was constructed and expressed in the Pichia pastoris expression system. There was 67-fold less toxicity of the fusion protein when compared with TNF- alone in cells expressing CA125. Furthermore, scFv-TNF was 10-fold more selective in cell killing directed by anti-CA125 scFv in a CA125-positive cell line than the CA125-negative line.     

Polymorphisms of the DNA repair gene MGMT and risk and progression of head and neck cancer

Methylating agents are involved in carcinogenesis, and the DNA repair protein O⁶-methylguanine-DNA methyltransferase (MGMT) removes methyl group from O⁶-methylguanine. Genetic variation in DNA repair genes has been shown to contribute to susceptibility to squamous cell carcinoma of the head and neck (SCCHN). We hypothesize that MGMT polymorphisms are associated with risk of SCCHN. In a hospital-based case–control study of 721 patients with SCCHN and 1234 cancer-free controls frequency-matched by age, sex and ethnicity, we genotyped four MGMT polymorphisms, two in exon 3, 16195C > T and 16286C > T and two in the promoter region, 45996G > T and 46346C > A. We found that none of these polymorphisms alone had a significant effect on risk of SCCHN. However, when these four polymorphisms were evaluated together by the number of putative risk genotypes (i.e. 16195CC, 16286CC, 45996GT + TT, and 46346CA + AA), a statistically significantly increased risk of SCCHN was associated with the combined genotypes with three to four risk genotypes, compared with those with zero to two risk genotypes (adjusted odds ratio (OR) = 1.27; 95% confidence interval (CI) = 1.05–1.53). This increased risk was also more pronounced among young subjects (OR = 1.81; 95% CI = 1.11–2.96), men (OR = 1.24; 95% CI = 1.00–1.55), ever smokers (OR = 1.25; 95% = 1.01–1.56), ever drinkers (OR = 1.29; 95% CI = 1.04–1.60), patients with oropharyngeal cancer (OR = 1.45; 95% CI = 1.12–1.87), and oropharyngeal cancer with regional lymph node metastasis (OR = 1.52; 95% CI = 1.16–1.89). In conclusion, our results suggest that any one of MGMT variants may not have a substantial effect on SCCHN risk, but a joint effect of several MGMT variants may contribute to risk and progression of SCCHN, particularly for oropharyngeal cancer, in non-Hispanic whites.     

Generation of GGTA1 biallelic knockout pigs via zinc-finger nucleases and somatic cell nuclear transfer

Genetically modified pigs are valuable models of human disease and donors of xenotransplanted organs.Conventional gene targeting in pig somatic cells is extremely inefficient.Zinc-finger nuclease(ZFN)technology has been shown to be a powerful tool for efficiently inducing mutations in the genome.However,ZFN-mediated targeting in pigs has rarely been achieved.Here,we used ZFNs to knock out the porcineα-1,3-galactosyl-transferase(GGTA1)gene,which generates Gal epitopes that trigger hyperacute immune rejection in pig-to-human transplantation.Primary pig fibroblasts were transfected with ZFNs targeting the coding region of GGTA1.Eighteen mono-allelic and four biallelic knockout cell clones were obtained after drug selection with efficiencies of 23.4%and 5.2%,respectively.The biallelic cells were used to produce cloned pigs via somatic cell nuclear transfer(SCNT).Three GGTA1 null piglets were born,and one knockout primary fibroblast cell line was established from a cloned fetus.Gal epitopes on GGTA1 null pig cells were completely eliminated from the cell membrane.Functionally,GGTA1 knockout cells were protected from complement-mediated immune attacks when incubated with human serum.This study demonstrated that ZFN is an efficient tool in creating gene-modified pigs.GGTA1 null pigs and GGTA1 null fetal fibroblasts would benefit research and pig-to-human transplantation.     

Synergistic Effects of GhSOD1 and GhCAT1 Overexpression in Cotton Chloroplasts on Enhancing Tolerance to Methyl Viologen and Salt Stresses

In plants, CuZn superoxide dismutase (CuZnSOD, EC l.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), and catalase (CAT, EC l.11.1.6) are important scavengers of reactive oxygen species (ROS) to protect the cell from damage. In the present study, we isolated three homologous genes (GhSOD1, GhAPX1, and GhCAT1) from Gossypium hirsutum. Overexpressing cassettes containing chimeric GhSOD1, GhAPX1, or GhCAT1 were introduced into cotton plants by Agrobacterium transformation, and overexpressed products of these genes were transported into the chloroplasts by transit peptide, as expected. The five types of transgenic cotton plants that overexpressed GhSOD1, GhAPX1, GhCAT1, GhSOD1 and GhAPX1 stack (SAT), and GhSOD1 and GhCAT1 stack (SCT) were developed. Analyses in the greenhouse showed that the transgenic plants had higher tolerance to methyl viologen (MV) and salinity than WT plants. Interestingly, SCT plants suffered no damage under stress conditions. Based on analyses of enzyme activities, electrolyte leakage, chlorophyll content, photochemical yield (Fv/Fm), and biomass accumulation under stresses, the SCT plants that simultaneously overexpressed GhSOD1 and GhCAT1 appeared to benefit from synergistic effects of two genes and exhibited the highest tolerance to MV and salt stress among the transgenic lines, while the SAT plants simultaneously overexpressing GhSOD1 and GhAPX1 did not. In addition, transgenic plants overexpressing antioxidant enzymes in their chloroplasts had higher tolerance to salt stress than those expressing the genes in their cytoplasms, although overall enzyme activities were almost the same. Therefore, the synergistic effects of GhSOD1 and GhCAT1 in chloroplasts provide a new strategy for enhancing stress tolerance to avoid yield loss.     

When did the ancestor of true bugs become stinky? Disentangling the phylogenomics of Hemiptera–Heteroptera

The phylogeny of true bugs (Hemiptera: Heteroptera), one of the most diverse insect groups in terms of morphology and ecology, has been the focus of attention for decades with respect to several deep nodes between the suborders of Hemiptera and the infraorders of Heteroptera. Here, we assembled a phylogenomic data set of 53 taxa and 3102 orthologous genes to investigate the phylogeny of Hemiptera–Heteroptera, and both concatenation and coalescent methods were used. A binode-control approach for data filtering was introduced to reduce the incongruence between different genes, which can improve the performance of phylogenetic reconstruction. Both hypotheses (Coleorrhyncha + Heteroptera) and (Coleorrhyncha + Auchenorrhyncha) received support from various analyses, in which the former is more consistent with the morphological evidence. Based on a divergence time estimation performed on genes with a strong phylogenetic signal, the origin of true bugs was dated to 290–268 Ma in the Permian, the time in Earth's history with the highest concentration of atmospheric oxygen. During this time interval, at least 1007 apomorphic amino acids were retained in the common ancestor of the extant true bugs. These molecular apomorphies are located in 553 orthologous genes, which suggests the common ancestor of the extant true bugs may have experienced large-scale evolution at the genome level.     

Epidemiological,Clinical and Serological Characteristics of Children with Coronavirus Disease 2019 in Wuhan: A Single-centered,Retrospective Study

In December 2019, SARS-CoV-2 was first detected in the samples obtained from three adult patients who suffered from an unknown viral pneumonia in Wuhan (Li et al. 2020). This unknown viral pneumonia is further named as coronavirus disease 2019 (COVID-19) by the World Health Organization. To date, the number of new COVID-19 cases has continued to skyrocket and the impact of SARS-CoV-2 on humans is far greater than any pathogen of this century in both breadth and depth. Previous studies have shown that adults with COVID-19 have symptoms of fever, dry cough, dyspnea, fatigue and lymphocytopenia. Moreover, COVID-19 is more likely to cause death in the elderly, especially those with chronic comorbidities (Huang et al. 2020). In Wuhan, more than 50, 000 COVID-19 cases have been confirmed, including over 780 pediatric patients, and only one child death case (Lu et al. 2020). Although the number of children cases was far fewer than that of adults, COVID-19 might endanger children's health and the information on children remains limited, especially in serological study. In the retrospective study, the investigators analyzed the epidemiological, clinical and serological characteristics of children with COVID-19 in Wuhan in the early stages of the outbreak, which might provide theoretical and practical help in controlling COVID-19 and similar emerging infectious diseases in the future.