Zebrafish brd2a and brd2b are paralogous members of the bromodomain-ET (BET) family of transcriptional coregulators that show structural and expression divergence

<p>Abstract</p> <p>Background</p> <p>Brd2 belongs to the bromodomain-extraterminal domain (BET) family of transcriptional co-regulators, and functions as a pivotal histone-directed recruitment scaffold in chromatin modification complexes affecting signal-dependent transcription. Brd2 facilitates expression of genes promoting proliferation and is implicated in apoptosis and in egg maturation and meiotic competence in mammals; it is also a susceptibility gene for juvenile myoclonic epilepsy (JME) in humans. The <it>brd2 </it>ortholog in <it>Drosophila </it>is a maternal effect, embryonic lethal gene that regulates several homeotic loci, including Ultrabithorax. Despite its importance, there are few systematic studies of <it>Brd2 </it>developmental expression in any organism. To help elucidate both conserved and novel gene functions, we cloned and characterized expression of <it>brd2 </it>cDNAs in zebrafish, a vertebrate system useful for genetic analysis of development and disease, and for study of the evolution of gene families and functional diversity in chordates.</p> <p>Results</p> <p>We identify cDNAs representing two paralogous <it>brd2 </it>loci in zebrafish, <it>brd2a </it>on chromosome 19 and <it>brd2b </it>on chromosome 16. By sequence similarity, syntenic and phylogenetic analyses, we present evidence for structural divergence of <it>brd2 </it>after gene duplication in fishes. <it>brd2 </it>paralogs show potential for modular domain combinations, and exhibit distinct RNA expression patterns throughout development. RNA <it>in situ </it>hybridizations in oocytes and embryos implicate <it>brd2a </it>and <it>brd2b </it>as maternal effect genes involved in egg polarity and egg to embryo transition, and as zygotic genes important for development of the vertebrate nervous system and for morphogenesis and differentiation of the digestive tract. Patterns of <it>brd2 </it>developmental expression in zebrafish are consistent with its proposed role in <it>Homeobox </it>gene regulation.</p> <p>Conclusion</p> <p>Expression profiles of zebrafish <it>brd2 </it>paralogs support a role in vertebrate developmental patterning and morphogenesis. Our study uncovers both maternal and zygotic contributions of <it>brd2</it>, the analysis of which may provide insight into the earliest events in vertebrate development, and the etiology of some forms of epilepsy, for which zebrafish is an important model. Knockdowns of <it>brd2 </it>paralogs in zebrafish may now test proposed function and interaction with homeotic loci in vertebrates, and help reveal the extent to which functional novelty or partitioning has occurred after gene duplication.</p

CRF-Like Diuretic Hormone Negatively Affects Both Feeding and Reproduction in the Desert Locust, Schistocerca gregaria

Diuretic hormones (DH) related to the vertebrate Corticotropin Releasing Factor (CRF) have been identified in diverse insect species. In the migratory locust, Locusta migratoria, the CRF-like DH (CRF/DH) is localized in the same neurosecretory cells as the Ovary Maturating Parsin (OMP), a neurohormone that stimulates oocyte growth, vitellogenesis and hemolymph ecdysteroid levels in adult female locusts. In this study, we investigated whether CRF-like DH can influence feeding and reproduction in the desert locust, Schistocerca gregaria. We identified two highly similar S. gregaria CRF-like DH precursor cDNAs, each of which also encodes an OMP isoform. Alignment with other insect CRF-like DH precursors shows relatively high conservation of the CRF/DH sequence while the precursor region corresponding to OMP is not well conserved. Quantitative real-time RT-PCR revealed that the precursor transcripts mainly occur in the central nervous system and their highest expression level was observed in the brain. Injection of locust CRF/DH caused a significantly reduced food intake, while RNAi knockdown stimulated food intake. Therefore, our data indicate that CRF-like DH induces satiety. Furthermore, injection of CRF/DH in adult females retarded oocyte growth and caused lower ecdysteroid titers in hemolymph and ovaries, while RNAi knockdown resulted in opposite effects. The observed effects of CRF/DH may be part of a wider repertoire of neurohormonal activities, constituting an integrating control system that affects food intake and excretion, as well as anabolic processes like oocyte growth and ecdysteroidogenesis, following a meal. Our discussion about the functional relationship between CRF/DH and OMP led to the hypothesis that OMP may possibly act as a monitoring peptide that can elicit negative feedback effects

Mycorrhiza abundance and biological activity of soil under iron-fertilized apple cultivar (Red Chief) grafted on different rootstocks grown on a calcareous soil

The aim of this study was to examine mycorrhizal spore abundance, its infection rate and biological activity of soil depending on different rootstock, Fe sources or Fe doses. A field experiment was carried out to determine the effects of rootstocks on mychorizal abundance and root infection as well as CO2 production and dehydrogenase activity of soil. Doses of 25,50 and 75g tree'1 Fe-EDDHA or FeSO4 were applied to apple trees (Red Chief cv.) grafted on dwarf (M9 and M26) and semi-dwarf (MM106) rootstocks. At flowering stages soil and root samples were collected and analyzed for their dehidrogenase activity, CO2 production, microbial biomass-C or mycorrhizal abundance and infection rate. Results revealed that neither rootstock nor Fe applications effect on mycorrhiza number in rhizosphere soil. The higher value was observed in the soil M26 planted and 75 g da-1 Fe-EDDHA applied plot (15 spores per g of soil). Therefore, infection rate showed significant variations related to rootstocks and Fe applications. The most adapted rootstocks was MM106 which 37.1 % of the roots infected by mycorrhiza. Fe-EDDHA was more effective than FeSO4 whereas both of them increased infection rate compared to control. There was no statistical difference between rootstocks in CO2 production; however, Fe-EDDHA is stimulated CO2 formation. The highest CO2 formation (11.55 mg C02 100 g soil1) observed in 50 g of Fe-EDDHA applied MM 106 plot whereas the lowest was in M26 plot where Fe application not realized. Dehydrogenase activity was not affected by Fe sources; however, increased Fe application increased dehydrogenase activity. Rootstock of MM 106 is statistically more effective on dehydrogenase and highest dehydrogenase value was observed in 50 g of Fe-EDDHA applied MM106 plot as 328 µg TPF 10 g soil-1. The highest biomass-C value was observed in 50 g of Fe-EDDHA applied MM106 plot, whereas the lowest was observed in 50 g of FeSO4 applied M9 plot. In general, Fe-EDDHA application was promote biomass-C more than FeSO4. Comparing to rootstocks, the highest effective rootstock was MM106 and followed by M26 and M29, respectively

The enquiry-based learning experience: an evaluation project

A research and nursing development initiative group consisting of health lecturers and lecturer practitioners set out to evaluate how learners and teachers felt about the introduction of an enquiry based learning (EBL) approach to education. Five focus groups, teachers (1 group) post-registration students (1 group) and preregistration diploma students (3 groups) were interviewed. Discussions were tape recorded, transcribed, and analysed. The results revealed that students and teachers held disparative views on the efficiency of EBL. Teachers, surprisingly, felt more doubtful and discouraged than learners. Several concerns were raised over the ability of EBL to establish a foothold in a curriculum more noted for a pedagogical stance on learning. © 2005 Elsevier Ltd. All rights reserved