Zygotic Expression (zygotic + expression)

Distribution by Scientific Domains

Selected Abstracts

Localization of RNAs in oocytes of Eleutherodactylus coqui, a direct developing frog, differs from Xenopus laevis

Yvonne M. Beckham
SummaryEleutherodactylus coqui develops directly on land to a frog. The large 3.5-mm oocyte of E. coqui has enough yolk to allow development without a feeding tadpole. In the smaller Xenopus laevis oocyte, 1.3 mm in diameter, mRNAs involved in germ layer formation, such as VegT and Vg1, are localized to the vegetal cortex of the oocyte. We hypothesized that an animal shift has occurred in the localization of the E. coqui Orthologs of VegT and Vg1 due to the large egg size. Through a combination of degenerate reverse transcriptase polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE), we cloned 1634 bp of EcVegT and 1377 bp of EcVg1. Northern blot analysis shows that the lengths of these transcripts are 2.5 kb and 1.3 kb, respectively. This result suggests that we have obtained the complete Vg1 transcript, although this transcript has an extremely short 3, untranslated region compared with X. laevis, 256 bp and 1268 bp, respectively. Zygotic expression of EcVegT closely resembles that of VegT, supporting their orthology. Radioactive RT-PCR and in situ hybridization demonstrated the presence of EcVegT and EcVg1 predominantly near the animal pole of the oocyte. RT-PCR showed that the animal blastomeres, formed from the first horizontal cleavage, inherit half of the EcVegT and EcVg1 transcripts, although they contain only about 1% of the embryo volume. Our results indicate major differences between the molecular organization of the eggs of X. laevis and E. coqui. [source]

Differential expression of CaMK-II genes during early zebrafish embryogenesis

Sarah C. Rothschild
Abstract CaMK-II is a highly conserved Ca2+/calmodulin-dependent protein kinase expressed throughout the lifespan of all vertebrates. During early development, CaMK-II regulates cell cycle progression and "non-canonical" Wnt-dependent convergent extension. In the zebrafish, Danio rerio, CaMK-II activity rises within 2 hr after fertilization. At the time of somite formation, zygotic expression from six genes (camk2a1, camk2b1, camk2g1, camk2g2, camk2d1, camk2d2) results in a second phase of increased activity. Zebrafish CaMK-II genes are 92,95% identical to their human counterparts in the non-variable regions. During the first three days of development, alternative splicing yields at least 20 splice variants, many of which are unique. Whole-mount in situ hybridization reveals that camk2g1 comprises the majority of maternal expression. All six genes are expressed strongly in ventral regions at the 18-somite stage. Later, camk2a1 is expressed in anterior somites, heart, and then forebrain. Camk2b1 is expressed in somites, mid- and forebrain, gut, retina, and pectoral fins. Camk2g1 appears strongly along the midline and then in brain, gut, and pectoral fins. Camk2g2 is expressed early in the midbrain and trunk and exhibits the earliest retinal expression. Camk2d1 is elevated early at somite boundaries, then epidermal tissue, while camk2d2 is expressed in discrete anterior locations, steadily increasing along either side of the dorsal midline and then throughout the brain, including the retina. These findings reveal a complex pattern of CaMK-II gene expression consistent with pleiotropic roles during development. Developmental Dynamics 236:295,305, 2007. 2006 Wiley-Liss, Inc. [source]

Microevolutionary support for a developmental hourglass: gene expression patterns shape sequence variation and divergence in Drosophila

Tami Cruickshank
SUMMARY A central goal of evolutionary developmental biology (Evo-Devo) is to synthesize comparative molecular developmental genetics and its description of the dynamic relationship between genotype and phenotype with the microevolutionary processes (mutation, random drift, and selection) of population genetics. To this end, we analyzed sequence variation of five gene classes that act sequentially to shape early embryo development in Drosophila: maternal, gap, pair-rule, segment polarity, and segment identity genes. We found two related patterns: (1) a microevolutionary pattern, wherein relative sequence variation within species is 2- to 3-fold higher for maternal-effect genes than for any other gene class; and, (2) a macroevolutionary pattern, wherein the relative sequence divergence among species for maternal-effect genes is 2- to 4-fold greater than for any other gene class. Both patterns are qualitatively and quantitatively consistent with the predictions of microevolutionary theory. Our findings connect within-species genetic variation to between-species divergence and shed light on the controversy over the existence of a "developmental hourglass," where mid-embryonic stages are more evolutionarily constrained than either earlier or later stages. Because maternal-effect genes experience relaxed selective constraint relative to zygotic-effect genes, they explore a wider mutational and phenotypic space. As a result, early acting maternal-effect genes diverge more widely across taxa and thereby broaden the base of the developmental hourglass. In contrast, later acting zygotic genes are relatively more constrained and limited in their diversification across taxa, narrowing the waist of the developmental hourglass. This pattern is obscured by genes with both maternal and zygotic expression, which experience the strongest evolutionary constraint. [source]


INSECT SCIENCE, Issue 2 2003
LIN Xin-da
Abstract Wg/Wnt signaling is a key signaling pathway in Drosophila. Many genes involved in Wingless(wg) signal transduction pathway downstream of Wg, or it s vertebrate Wg homologue Wnt, have been identified. Transduction of the Wg signal downstream of Wg is mediated by nuclear TCF/LEF-1, through association with Armadillo (Arm),-catenin. Pygopus (pygo) is a new identified component in this pathway. Cellular localization experiment showed that pygo was expressed specifically in the nucleus. The expression profile of pygo in embryos was examined using in situ hybridization. Although pygo expressed ubiquitously in the embryos, it expressed at relatively high level in pre-blastoderm embryos which indicate a high degree of maternally provided message, followed by a low level of ubiquitous zygotic expression. This continues into larval tissues (including wing disc, eye disc and leg disc), where pygo appears to be expressed at low level. Comparison of pygo expression levels, in the wing disc, eye disc and leg disc, showed pygo expression level in the wing disc pouch and leg disc were relative higher. [source]