Changing Base Ratios in RNA of Developing Tissues of Xenopus laevis

Abstract

THE new forms of RNA synthesized during embryonic development of the South African clawed toad, Xenopus laevis, have come under investigation recently by Brown and Gurdon¹ and are discussed more fully by Brown and Littna². Since their work was concerned only with events in the embryo as a whole, we have undertaken a study of possible differences in the new forms of RNA synthesized in different tissue primordia of this species. In the preliminary work to be reported here, the nucleotide composition of the total acid-insoluble RNA extracted both from whole embryos and from ectoderm undergoing three different courses of differentiation—into neural plate, neural crest and epidermis—has been analysed. Although data published by Ycas³ indicated that different tissues of the adult rat do not show any significant differences in their RNA composition, there have been several other reports^4–7 of altered base ratios in UNA of tissue cells undergoing special phases of modified protein synthesis in response to external stimuli. It seemed likely, therefore, that embryonic tissues responding to stimuli such as neural induction might also show some alterations of RNA base ratios. As will be reported here, RNA extracts both from whole embryos and from the isolated ectoderm do, in fact, exhibit some changes in base ratios, which are of general interest in view of the protein syntheses known to be occurring at these stages of development.