Meeting Abstract

73.6  Sunday, Jan. 6  Molecular mechanisms of receptor-mediated yolk uptake underlying phenotypic variation in egg size HAN, D*; WILLIAMS, T.D.; Simon Fraser University dongh@sfu.ca

Natural selection acts on variation within species, and thus studying intraspecific or inter-individual variation is necessary to understand the evolution of phenotypic variation in life-history traits. However, our knowledge of the mechanisms underlying inter-individual variation in phenotype remains rudimentary especially at the cellular and molecular level. How does inter-individual variation in cellular and molecular processes correlate with phenotype at the organism level? We have been investigating the molecular basis of inter-individual variation in egg size, a key, and widely-studied, life-history trait but one for which the causes and consequences of variation remain poorly understood. Previous work (J. Comp. Physiol. B 171:255) suggested that inter-individual variation in size of yolky follicles was correlated with rate of yolk uptake, measured indirectly using radio-labeled amino acid, i.e. that receptor-mediated yolk uptake might be a key determinant of yolk and egg size. In our study, we measured vitellogenin receptor (VTG-R) mRNA expression levels in developing follicles of individual female zebra finches (Taeniopygia guttata) using real-time- PCR. We will present data on a) comparison of sequence data for VTG-R and VTG-R mRNA between zebra finches and other species; b) temporal variation in VTG-R mRNA expression in relation to different stages of follicle development (e.g. non-breeding, white follicles, F3, F2, F1 yolky follicles), and c) inter-individual variation in VTG-R mRNA expression at specific stages of follicle development in relation to phenotypic variation in follicle, yolk and egg size.