Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Spadefoot toads are dormant underground for 9-10 months each year and emerge only with summer rains to briefly breed and feed. To identify changes in gene expression associated with estivation, a cDNA library was constructed from liver of female toads and differentially screened with total RNA from awake versus estivating animals. A clone showing 60 % higher expression in liver of estivators was characterized. Sequencing revealed a 1053 nucleotide full-length cDNA; the largest open reading frame was 708 nucleotides, encoding a protein of 235 amino acids. Homology search in Genbank identified riboflavin binding protein (RBP), a monomeric phosphoglycoprotein produced by liver of female birds, reptiles and mammals that binds plasma riboflavin to load the vitamin into eggs or fetus. To our knowledge, this is the first report of RBP in amphibians. Toad RBP showed 50 % identity with chicken or turtle RBP and essential features were conserved including 18 cysteine residues, two asparagine glycosylation sites and 6 tryptophan residues. However, a region with 8 phosphoserines in chicken or turtle RBP that is key for oocyte membrane binding had only 3 serines in toad RBP. Upregulation of RBP in liver of estivating toads may support egg maturation prior to the explosive breeding that occurs immediately upon emergence.

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Poster Number PAstorey0150
Keywords: metabolic arrest, gene upregulation, vitamin binding, amphibian, stress adaptation