Molecular evolution in the Drosophila melanogaster species subgroup: frequent parameter fluctuations on the timescale of molecular divergence

Although mutation, genetic drift, and natural selection are well established as determinants of genome evolution, the importance (frequency and magnitude) of parameter fluctuations in molecular evolution is less understood. DNA sequence comparisons among closely related species allow specific substitutions to be assigned to lineages on a phylogenetic tree. In this study, we compare patterns of codon usage and protein evolution in 22 genes (>11,000 codons) among Drosophila melanogaster and five relatives within the D. melanogaster subgroup. We assign changes to eight lineages using a maximum-likelihood approach to infer ancestral states. Uncertainty in ancestral reconstructions is taken into account, at least to some extent, by weighting reconstructions by their posterior probabilities. Four of the eight lineages show potentially genomewide departures from equilibrium synonymous codon usage; three are decreasing and one is increasing in major codon usage. Several of these departures are consistent with lineage-specific changes in selection intensity (selection coefficients scaled to effective population size) at silent sites. Intron base composition and rates and patterns of protein evolution are also heterogeneous among these lineages. The magnitude of forces governing silent, intron, and protein evolution appears to have varied frequently, and in a lineage-specific manner, within the D. melanogaster subgroup.     

The role of the Ser/Thr cluster in the phosphorylation of PPPSP motifs in Wnt coreceptors

Wnt/β-catenin signaling controls a variety of cellular processes, including cell growth, oncogenesis, and development. Upon Wnt stimulation, the intracellular region of the coreceptor, LRP6 or 5, is phosphorylated by the membrane-recruited GSK3β and CK1. The cytoplasmic domain of LRP6/5 contains one Ser/Thr cluster and the PPPSP motifs, both of which are essential for propagation of the signal. While the phosphorylated PPPSP motifs are known to directly inhibit GSK3β, the biochemical role of the phosphorylated Ser/Thr cluster remains to be elucidated. Herein, we reveal that the Ser/Thr cluster plays an important role in the phosphorylation of the PPPSP motif. Interestingly, we observe that GSK3β activity on the PPPSP motif requires a high ATP concentration, close to that of the physiological condition. Taken together, these data suggest that the phosphorylated Ser/Thr cluster serves as a docking site for GSK3β to promote the phosphorylation of the PPPSP motif. Our results provide insight into the molecular mechanism for the initial events of the Wnt/β-catenin signaling.     

Crystal Structure of the Periplasmic Component of a Tripartite Macrolide-Specific Efflux Pump

In Gram-negative bacteria, type I protein secretion systems and tripartite drug efflux pumps have a periplasmic membrane fusion protein (MFP) as an essential component. MFPs bridge the outer membrane factor and an inner membrane transporter, although the oligomeric state of MFPs remains unclear. The most characterized MFP AcrA connects the outer membrane factor TolC and the resistance-nodulation-division-type efflux transporter AcrB, which is a major multidrug efflux pump in Escherichia coli. MacA is the periplasmic MFP in the MacAB-TolC pump, where MacB was characterized as a macrolide-specific ATP-binding-cassette-type efflux transporter. Here, we report the crystal structure of E. coli MacA and the experimentally phased map of Actinobacillus actinomycetemcomitans MacA, which reveal a domain orientation of MacA different from that of AcrA. Notably, a hexameric assembly of MacA was found in both crystals, exhibiting a funnel-like structure with a central channel and a conical mouth. The hexameric MacA assembly was further confirmed by electron microscopy and functional studies in vitro and in vivo. The hexameric structure of MacA provides insight into the oligomeric state in the functional complex of the drug efflux pump and type I secretion system.     

VEGF165对血管内皮细胞内Mg^2＋浓度调节机制的研究

目的：探讨血管内皮生长因子165（VEGF165）对人脐带静脉内皮细胞（HLNECs）内游离镁离子浓度（[Mg^2＋]i）的调节机制.方法：采用荧光指示剂mag-fura-2及运用PTi阳离子测定系统动态检测HUVECs的[Mg^2＋].结果：经酪氨酸激酶阻断剂（tryrphostin A23和genistein）,磷脂酰3激酶阻断剂（wortmannin和LY294002）,磷脂酶Cγ阻断剂（U73122）预处理,均显著阻断VEGF165诱导的[Mg^2＋]i增加.但经磷脂酶C阻断剂无活性的类似物（U73343）和增殖激活蛋白激酶阻断剂（SB202190和PD9S059）预处理,不能阻断VEGF165诱导的[Mg^2＋]i增加：结论：VEGF165通过酪氨酸激酶／磷脂酰3激酶／磷脂酶口信号转导途径使细胞内的Mg^2＋库释和Mg^2＋,从而增加HUVECs的[Mg^2＋]i.     

转基因技术在玉米遗传育种中的应用

玉米转基因育种是通过基因转移方法创造玉米新种质或新品种。将转基因技术与玉米常规育种技术相结合,能尽快地培育出符合育种目标的新品种,带来了育种水平的提高、创新和突破,加快了玉米育种进程。论述了转基因技术在玉米育种中的主要应用方法、研究进展及应用现状。随着转基因技术的飞速发展及其研究的日趋成熟,转基因技术在拓宽玉米种质资源、提高杂交种的抗逆性、抗病虫性、提高产量和品质等方面将发挥更大的作用,应用前景广阔。     

Synthesis of 2-(4-substituted benzyl-1,4-diazepan-1-yl)-N-(3,4-dihydro-3-oxo-2H-benzo[b][1,4]oxazin-7-yl)acetamides and their positive inotropic evaluation

Herein we describe the discovery of compound 3g, a potent positive inotropic agent compared with the standard drug, milrinone. Compound 3g was developed from a series of 2-(4-substitutedbenzyl-1,4-diazepan-1-yl)-N-(3,4-dihydro-3-oxo-2H-benzo[b][1,4]oxazin-7-yl) acetamides found in an evaluation of inotropic activity by measuring left atrium stroke volume on isolated rabbit heart preparations. Several compounds showed favorable activities, but 3g was the most potent, with 7.68 ± 0.14% increased stroke volume (milrinone 2.38 ± 0.05%) at 1 × 10^?5 M in our in vitro study. The chronotropic effects of compounds having significant inotropic effects were also evaluated.     

Fine mapping and candidate gene analysis of the floury endosperm gene, FLO(a), in rice

In addition to its role as an energy source for plants, animals and humans, starch is also an environmentally friendly alternative to fossil fuels. In rice, the eating and cooking quality of the grain is determined by its starch properties. The floury endosperm of rice has been explored as an agronomical trait in breeding and genetics studies. In the present study, we characterized a floury endosperm mutant, flo(a), derived from treatment of Oryza sativa ssp. japonica cultivar Hwacheong with MNU. The innermost endosperm of the flo(a) mutant exhibited floury characteristics while the outer layer of the endosperm appeared normal. Starch granules in the flo(a) mutant formed a loosely-packed crystalline structure and X-ray diffraction revealed that the overall crystallinity of the starch was decreased compared to wild-type. The FLO(a) gene was isolated via a map-based cloning approach and predicted to encode the tetratricopeptide repeat domaincontaining protein, OsTPR. Three mutant alleles contain a nucleotide substitution that generated one stop codon or one splice site, respectively, which presumably disrupts the interaction of the functionally conserved TPR motifs. Taken together, our map-based cloning approach pinpointed an OsTPR as a strong candidate of FLO(a), and the proteins that contain TPR motifs might play a significant role in rice starch biosynthetic pathways.     

Biomass carbon stocks in China’s forests between 2000 and 2050: A prediction based on forest biomass-age relationships

China’s forests are characterized by young forest age, low carbon density and a large area of planted forests, and thus have high potential to act as carbon sinks in the future. Using China’s national forest inventory data during 1994–1998 and 1999–2003, and direct field measurements, we investigated the relationships between forest biomass density and forest age for 36 major forest types. Statistical approaches and the predicted future forest area from the national forestry development plan were applied to estimate the potential of forest biomass carbon storage in China during 2000–2050. Under an assumption of continuous natural forest growth, China’s existing forest biomass carbon (C) stock would increase from 5.86 Pg C (1 Pg=10¹⁵ g) in 1999–2003 to 10.23 Pg C in 2050, resulting in a total increase of 4.37 Pg C. Newly planted forests through afforestation and reforestation will sequestrate an additional 2.86 Pg C in biomass. Overall, China’s forests will potentially act as a carbon sink for 7.23 Pg C during the period 2000–2050, with an average carbon sink of 0.14 Pg C yr⁻¹. This suggests that China’s forests will be a significant carbon sink in the next 50 years.     

Dkk4 and Eda Regulate Distinctive Developmental Mechanisms for Subtypes of Mouse Hair

The mouse hair coat comprises protective “primary” and thermo-regulatory “secondary” hairs. Primary hair formation is ectodysplasin (Eda) dependent, but it has been puzzling that Tabby (Eda ^-/y) mice still make secondary hair. We report that Dickkopf 4 (Dkk4), a Wnt antagonist, affects an auxiliary pathway for Eda-independent development of secondary hair. A Dkk4 transgene in wild-type mice had no effect on primary hair, but secondary hairs were severely malformed. Dkk4 action on secondary hair was further demonstrated when the transgene was introduced into Tabby mice: the usual secondary follicle induction was completely blocked. The Dkk4-regulated secondary hair pathway, like the Eda-dependent primary hair pathway, is further mediated by selective activation of Shh. The results thus reveal two complex molecular pathways that distinctly regulate subtype-based morphogenesis of hair follicles, and provide a resolution for the longstanding puzzle of hair formation in Tabby mice lacking Eda.