高温胁迫及其持续时间对棉蚜死亡和繁殖的影响

为探索高温胁迫对棉蚜的影响,室内采用叶子圆片培养基饲养棉蚜的方法,研究不同温度(32,34,36,38,40℃)、不同处理时间(1,2,4,6h)对棉蚜死亡和繁殖的影响.结果表明:棉蚜每日死亡率可用互补重对数模型较好地拟合.随着温度的升高和持续天数的延长,棉蚜累计死亡率呈上升趋势,38 ℃条件下其累计死亡率明显迅速上升.棉蚜半数致死温度随着每天高温处理时间的增加和高温持续天数的延长而降低,且第1-2天下降明显.棉蚜繁殖率随着温度的升高呈下降趋势,每天处理时间不同其繁殖率规律不同,但均是在38℃时下降最多.38℃可能是棉蚜耐高温能力的拐点.研究结果为提高棉蚜种群预测准确性、科学决策最佳化学防治时间提供依据.     

Demonstration of the cellular expression of genes encoding molt-inhibiting hormone and crustacean hyperglycemic hormone in the eyestalk of the shore crab Carcinus maenas

Based on the amino acid sequence of the molt-inhibiting hormone of Carcinus maenas, two degenerated oligonucleotide primers were synthesized and used in the polymerase chain reaction. By use of complementary DNA of a library constructed from medulla terminalis-X-organ RNA of C. maenas as template, the specific complementary DNA between the primers was amplified, cloned and sequenced. This strategy revealed a DNA sequence for which the deduced amino acid sequence is identical to the recently published C. maenas molt-inhibiting hormone sequence as determined by Edman degradation. Visualization of messenger RNAs encoding molt-inhibiting hormone and crustacean hyperglycemic hormone in different perikarya of the X-organ was obtained using digoxigenin-labelled complementary RNA probes. Combination of immunocytochemical staining using polyclonal antisera against the native C. maenas neuropeptides and in situ hybridization performed on alternating sections confirmed the specificity of the reaction. The results show that there is no co-localization of molt-inhibiting hormone and crustacean hyperglycemic hormone at the messenger RNA and the protein level.     

A quantitative measure of error minimization in the genetic code

Summary We have calculated the average effect of changing a codon by a single base for all possible single-base changes in the genetic code and for changes in the first, second, and third codon positions separately. Such values were calculated for an amino acid's polar requirement, hydropathy, molecular volume, and isoelectric point. For each attribute the average effect of single-base changes was also calculated for a large number of randomly generated codes that retained the same level of redundancy as the natural code. Amino acids whose codons differed by a single base in the first and third codon positions were very similar with respect to polar requirement and hydropathy. The major differences between amino acids were specified by the second codon position. Codons with U in the second position are hydrophobic, whereas most codons with A in the second position are hydrophilic. This accounts for the observation of complementary hydropathy. Single-base changes in the natural code had a smaller average effect on polar requirement than all but 0.02% of random codes. This result is most easily explained by selection to minimize deleterious effects of translation errors during the early evolution of the code.     

Cadherin 23 is a component of the transient lateral links in the developing hair bundles of cochlear sensory cells

Cadherin 23 is required for normal development of the sensory hair bundle, and recent evidence suggests it is a component of the tip links, filamentous structures thought to gate the hair cells' mechano-electrical transducer channels. Antibodies against unique peptide epitopes were used to study the properties of cadherin 23 and its spatio-temporal expression patterns in developing cochlear hair cells. In the rat, intra- and extracellular domain epitopes are readily detected in the developing hair bundle between E18 and P5, and become progressively restricted to the distal tip of the hair bundle. From P13 onwards, these epitopes are no longer detected in hair bundles, but immunoreactivity is observed in the apical, vesicle-rich, pericuticular region of the hair cell. In the P2-P3 mouse cochlea, immunogold labeling reveals cadherin 23 is associated with kinocilial links and transient lateral links located between and within stereociliary rows. At this stage, the cadherin 23 ectodomain epitope remains on the hair bundle following BAPTA or La(3+) treatment, but is lost following exposure to the protease subtilisin. In contrast, mechano-electrical transduction is abolished by BAPTA but unaffected by subtilisin. These results suggest cadherin 23 is associated with transient lateral links that have properties distinct from those of the tip-link.     

The template RNAs of RNA polymerases can have compact secondary structure, formed by long double helices with partial violations of the complementarity

A new method of contextual analysis was used to search the long non-random inverted repeats and the complementary palindromes in the genes of E. coli and T7 RNA polymerases. These genes were found to contain from 25% to 50% of all the nucleotides involved in such helices. The 5' -and 3' -ends of mRNA can be protected by neighbouring double helices from the nuclease attack. Some double helices are competing and very similar to the attenuator of E. coli trp-operon.     

Therapeutic options for triple-negative breast cancers with defective homologous recombination

Breast cancer is the most common malignancy among women in developed countries, affecting more than a million women per year worldwide. Over the last decades, our increasing understanding of breast cancer biology has led to the development of endocrine agents against hormone receptor-positive tumors and targeted therapeutics against HER2-expressing tumors. However, no targeted therapy is available for patients with triple-negative breast cancer, lacking expression of hormone receptors and HER2. Overlap between BRCA1-mutated breast cancers and triple-negative tumors suggests that an important part of the triple-negative tumors may respond to therapeutics targeting BRCA1-deficient cells. Here, we review the features shared between triple-negative, basal-like and BRCA1-related breast cancers. We also discuss the development of novel therapeutic strategies to target BRCA1-mutated tumors and triple-negative tumors with BRCA1-like features. Finally, we highlight the utility of mouse models for BRCA1-mutated breast cancer to optimize (combination) therapy and to understand drug resistance.     

CpcF-dependent regulation of pigmentation and development in Fremyella diplosiphon

Cyanobacteria harvest light for photosynthesis using photosynthetic light-harvesting complexes called phycobilisomes (PBSs). Lyases are enzymes responsible for covalent attachment of light-absorbing chromophores to the phycobiliproteins (PBPs) contained in PBSs. We isolated a pigmentation mutant in the filamentous cyanobacterium Fremyella diplosiphon and determined that it possesses an insertional mutation in cpcF, which encodes one component of a heterodimeric phycocyanin lyase. Here, we discuss the implications of the mutation in cpcF on light-dependent pigmentation and morphology responses characteristic of complementary chromatic adaptation in F. diplosiphon. Although cpcF encodes a phycocyanin lyase, significant decreases in the levels of all classes of PBPs are associated with CpcF deficiency in F. diplosiphon. Notably, CpcF deficiency has a limited effect on the shape of F. diplosiphon cells, but significantly impacts filament length. Possible mechanisms for the broad impact of CpcF deficiency on pigmentation and filament morphology are discussed.     

Molecular cloning,characterization and expression of myoglobin in Tibetan antelope (Pantholops hodgsonii), a species with hypoxic tolerance

The Tibetan antelope (Pantholops hodgsonii) is a hypoxia-tolerant species that lives at an altitude of 4000–5000 m above sea level on the Qinghai–Tibetan plateau. Myoglobin is an oxygen-binding cytoplasmic hemoprotein that is abundantly expressed in oxidative skeletal and cardiac myocytes. Numerous studies have implicated that hypoxia regulates myoglobin expression to allow adaptation to conditions of hypoxic stress. Few studies have yet looked at the effect of myoglobin on the adaptation to severe environmental stress on TA. To investigate how the Tibetan antelope (TA) has adapted to a high altitude environment at the molecular level, we cloned and analyzed the myoglobin gene from TA, compared the expression of myoglobin mRNA and protein in cardiac and skeletal muscle between TA and low altitude sheep. The results indicated that the full-length myoglobin cDNA is composed of 1154 bp with a 111 bp 5′ untranslated region (UTR), a 578 bp 3′ UTR and a 465 bp open reading frame (ORF) encoding a polypeptide of 154 amino acid residues with a predicted molecular weight of 17.05 kD. The TA myoglobin cDNA sequence and the deduced amino acid sequence were highly homologous with that of other species. When comparing the myoglobin sequence from TA with the Ovis aries myoglobin sequence, variations were observed at codons 21 (GGT → GAT) and 78 (GAA → AAG), and these variations lead to changes in the corresponding amino acids, i.e., Gly → Asp and Glu → Lys, respectively. But these amino acid substitutions are unlikely to effect the ability of binding oxygen because their location is less important, which is revealed by the secondary structure and 3D structure of TA myoglobin elaborated by homology modeling. However, the results of myoglobin expression in cardiac and skeletal muscles showed that they were both significantly higher than that in plain sheep not only in mRNA but also protein level. We speculated that the higher expression of myoglobin in TA cardiac and skeletal muscles improves their ability to obtain and store oxygen under hypoxic conditions. This study indicated that TA didn't improve the ability of carrying oxygen by changing the molecular structure of myoglobin, but through increasing the expression of myoglobin in cardiac and skeletal muscles.     

Identification of a Bombyx mori gene encoding small heat shock protein BmHsp27.4 expressed in response to high-temperature stress

Elucidating the mechanisms underlying the response and resistance to high-temperature stress in the Lepidoptera is essential for understanding the effect of high-temperature on the regulation of gene expression. A tag (CATGAACGTGAAGAGATTCAG) matching the predicted gene BGIBMGA005823-TA in SilkDB identified the most significant response to high-temperature stress in a screen of the heat-treated digital gene expression library of Bombyx mori (B. mori) (Unpublished data). BLAST and RACE showed that the gene is located on chromosome 5 and has an open reading frame (ORF) of 741 bp. Phylogenetic analysis found that B. mori small heat shock protein 27.4 (BmHSP27.4) is in an evolutionary branch separate from other small heat shock proteins. Expression analysis showed that BmHsp27.4 is highly expressed in brain, eyes and fat bodies in B. mori. Its mRNA level was elevated at high-temperature and this increase was greater in females. The ORF without the signal peptide sequence was cloned into vector pET-28a(+), transformed and over-expressed in Escherichia coli Rosetta (DE3). Western blotting and immunofluorescence analysis with a polyclonal antibody, confirmed that the level of protein BmHSP27.4 increased at a high-temperature, in accordance with its increased mRNA level. In this study, BmHsp27.4 was identified as a novel B. mori gene with an important role in response to high-temperature stress.