Home About us Contact
|
Home About us Contact | ||
|
|
||
Functional Diversification (functional + diversification)
Selected AbstractsAn ecdysteroid-inducible insulin-like growth factor-like peptide regulates adult development of the silkmoth Bombyx moriFEBS JOURNAL, Issue 5 2009Naoki Okamoto Insulin-like growth factors (IGFs) play essential roles in fetal and postnatal growth and development of mammals. They are secreted by a wide variety of tissues, with the liver being the major source of circulating IGFs, and regulate cell growth, differentiation and survival. IGFs share some biological activities with insulin but are secreted in distinct physiological and developmental contexts, having specific functions. Although recent analyses of invertebrate genomes have revealed the presence of multiple insulin family peptide genes in each genome, little is known about functional diversification of the gene products. Here we show that a novel insulin family peptide of the silkmoth Bombyx mori, which was purified and sequenced from the hemolymph, is more like IGFs than like insulin, in contrast to bombyxins, which are previously identified insulin-like peptides in B. mori. Expression analysis reveals that this IGF-like peptide is predominantly produced by the fat body, a functional equivalent of the vertebrate liver and adipocytes, and is massively released during pupa,adult development. Studies using in vitro tissue culture systems show that secretion of the peptide is stimulated by ecdysteroid and that the secreted peptide promotes the growth of adult-specific tissues. These observations suggest that this peptide is a Bombyx counterpart of vertebrate IGFs and that functionally IGF-like peptides may be more ubiquitous in the animal kingdom than previously thought. Our results also suggest that the known effects of ecdysteroid on insect adult development may be in part mediated by IGF-like peptides. [source] Urban Polycentricity and the Costs of Commuting: Evidence from Italian Metropolitan AreasGROWTH AND CHANGE, Issue 3 2010PAOLO VENERI ABSTRACT Polycentricity at the metropolitan scale is perhaps the model of spatial organisation that needs to be investigated more thoroughly as regards its effects on travel. The aim of this paper is to test the role of polycentricity,as well as other spatial characteristics, such as compactness, functional diversification and size,in the costs of commuting, taking into account an external cost component (per-capita CO2 emissions) and a private cost component (time spent on travelling). The degree of urban polycentricity has been measured by adopting a dynamic approach based on commuting flows and on social network analysis tools. The analysis is carried out using a database of 82 Italian metropolitan areas (MAs). Results show that MAs with a higher degree of polycentricity are more virtuous both in terms of private and external costs of mobility, while the degree of compactness is associated with lower environmental costs but with higher private costs. Size is associated with both higher external and private costs, while the role of functional diversification turns out to be statistically insignificant. Socio-demographics also play a role. [source] DC characteristics and high frequency response of GaN nanowire metal-oxide-semiconductor field-effect transistorPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Jeng-Wei Yu Abstract We report selected site lateral growth of crystalline [110] GaN nanowire (NW) with high channel mobility of 1050 cm2/V-s on SiO2/p-Si. This scheme enables photolithographic fabrication of top-gated GaN NW-MOSFET of 60 nm dia. and 2 ,m gate length. Device parameters with gm of 25 ,S, saturation current of 90 ,A, and cut-off frequency fT at 14 GHz have been extracted. In an active load configuration of GaN NW-MOSFET inverter we reported voltage gain of 2 and a high current on/off ratio of 104. These observations suggest promising functional diversification of the GaN NW-MOSFET on the Si-based CMOS platform for the sub-50 nm technology nodes. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Functionally redundant SHI family genes regulate Arabidopsis gynoecium development in a dose-dependent mannerTHE PLANT JOURNAL, Issue 1 2006Sandra Kuusk Summary Gene duplication events, and the subsequent functional divergence of duplicates, are believed to be important evolutionary agents, driving morphological diversification. We have studied the structural and functional diversification of members of a plant-specific gene family in Arabidopsis thaliana by analysing mutant phenotypes, expression patterns and phylogeny. The SHI gene family comprises ten members that encode proteins with a RING finger-like zinc finger motif. We show that, despite being highly divergent in sequence, except in two conserved regions, many of the SHI -related genes are partially redundant in function and synergistically promote gynoecium, stamen and leaf development in Arabidopsis. Gynoecia of the loss-of-function sty1-1 mutant display subtle morphological defects, and, although mutations in the related STY2, SHI, SRS3, SRS4, SRS5, SRS7 and LRP1 genes have no apparent effect on gynoecium development, the sty1-1 mutant phenotype is gradually enhanced in double, triple, quadruple and quintuple mutant combinations, suggesting a remarkably extensive functional conservation within the family, which appears to be based on dosage dependency and protection against dominant negative mutations. In multiple mutant lines, all marginal tissues in the apical part of the gynoecium are dramatically reduced or missing, and our data indicate that SHI family members may promote formation of these tissues downstream of the transcriptional co-repressor LEUNIG (LUG). [source] Comparative genomics enabled the isolation of the R3a late blight resistance gene in potatoTHE PLANT JOURNAL, Issue 2 2005Sanwen Huang Summary Comparative genomics provides a tool to utilize the exponentially increasing sequence information from model plants to clone agronomically important genes from less studied crop species. Plant disease resistance (R) loci frequently lack synteny between related species of cereals and crucifers but appear to be positionally well conserved in the Solanaceae. In this report, we adopted a local RGA approach using genomic information from the model Solanaceous plant tomato to isolate R3a, a potato gene that confers race-specific resistance to the late blight pathogen Phytophthora infestans. R3a is a member of the R3 complex locus on chromosome 11. Comparative analyses of the R3 complex locus with the corresponding I2 complex locus in tomato suggest that this is an ancient locus involved in plant innate immunity against oomycete and fungal pathogens. However, the R3 complex locus has evolved after divergence from tomato and the locus has experienced a significant expansion in potato without disruption of the flanking colinearity. This expansion has resulted in an increase in the number of R genes and in functional diversification, which has probably been driven by the co-evolutionary history between P. infestans and its host potato. Constitutive expression was observed for the R3a gene, as well as some of its paralogues whose functions remain unknown. [source] Otx1 gene-controlled morphogenesis of the horizontal semicircular canal and the origin of the gnathostome characteristicsEVOLUTION AND DEVELOPMENT, Issue 4 2000Sylvie Mazan SUMMARY The horizontal semicircular canal of the inner ear is a unique feature of gnathostomes and is predated by the two vertical semicircular canals, which are already present in lampreys and some fossil, armored jawless vertebrates regarded as close relatives of gnathostomes. Inactivation in mice of the orthodenticle -related gene Otx1 results in the absence of this structure. In bony fishes and tetrapods (osteichthyans), this gene belongs to a small multigene family comprising at least two orthology classes, Otx1 and Otx2. We report that, as in the mouse, xenopus and zebrafish, Otx1- and Otx2 -related genes are present in a chondrichthyan, the dogfish Scyliorhinus canicula, with an Otx1 expression domain in the otocyst very similar to those observed in osteichthyans. A strong correlation is thus observed in extant vertebrates between the distribution of the horizontal semicircular canal and the presence of an Otx1 ortholog expressed in the inner ear, which supports the hypothesis that the absence of this characteristic in Otx1 -/- mice may correspond to an atavism. The same conclusion applies to two other gnathostome-specific characteristics also deleted in Otx1 -/- mice, the utriculosaccular duct and the ciliary process. Together with functional analyses of Otx1 and Otx2 genes in mice and comparative analyses of the Otx gene families characterized in chordates, these discoveries lead to the hypothesis that some of the anatomic characteristics of gnathostomes have appeared quite suddenly and almost simultaneously in vertebrate evolution, possibly as a consequence of gene functional diversifications following duplications of an ancestral chordate gene. [source] | ||||||||||