β-catenin is thought to mediate cell fate specification events by localizing to the nucleus where it modulates gene expression. To ask whether β-catenin is involved in cell fate specification during sea urchin embryogenesis, we analyzed the distribution of nuclear β-catenin in both normal and experimentally manipulated embryos. In unperturbed embryos, β-catenin accumulates in nuclei that includ...

The amphibian embryo develops into the three germ layers in a predictable fashion, the pigmented animal pole forming the ectoderm, the yolky vegetal pole forming the endoderm and the mesoderm developing from an annulus at the equator. Mesoderm formation is believed to require a TGF-β family signal originating from vegetal cells because a truncated dominant negative activin receptor, promiscuous...

In an effort to understand how polarity is established in Xenopus oocytes, we have analyzed the process of localization of the maternal mRNA, Vg1. In fully grown oocytes, Vg1 mRNA is tightly localized at the vegetal cortex. Biochemical fractionation shows that the mRNA is preferentially associated with a detergent-insoluble subcellular fraction. The use of cytoskeletal inhibitors suggests that ...

Nitric oxide (⋅NO) is known to attenuate dormancy and promote germination, a function that seemingly depends on crosstalk with the abscisic acid (ABA) signaling network. In the past 2 years, a number of independent studies have revealed that ⋅NO gates the ABA signaling network at multiple steps, ensuring redundant and effectively irreversible control of germination. Here we summarize the recent...

The role of cytoplasmic domains in the determination of the fates of ectodermal and mesodermal cells has been investigated in leech embryos. When yolk-deficient cytoplasm (teloplasm) was extruded from the animal pole of the zygote, the ectodermal precursor blastomere was converted to a mesodermal fate. This change of fate can be prevented by replacement of the extruded animal teloplasm with tel...

One of the earliest and most-fundamental pattern- formation events in embryonic development is endoderm and mesoderm specification. In sea urchin embryos, this process begins with blimp1 and wnt8 gene expression at the vegetal pole as soon as embryonic transcription begins. Shortly afterwards, wnt8/blimp1 expression spreads to the adjacent ring of mesoderm progenitor cells and is extinguished i...