On the mode of activation of sequestered messengers in Artemia salina

Activation of the dormant embryos of Artemia salina was marked by a rapid increase in 32P uptake which reached a stationary phase after 6 h of activation. The increase in 32P uptake by whole cysts was paralleled by its incorporation into nucleotides. Fractionation of acid-soluble nucleotides and alkaline hydrolysate of nucleic acids on Dowex-1-formate column revealed the 32P radioactivity to be exclusively localised in AMP. Analysis of the labelled RNA species extracted at different stages of development indicated a preferential labelling of small molecular weight species till the emergence of the embryos, followed by the de novo synthesis of messenger and stable RNA species in later stages of development. During early development, polyadenylated RNA species were localised in the particulate fraction sedimenting at 16,000 rpm and their location shifted to the soluble fraction as development proceeded. Activation of performed messengers by phosphorylation of the adenylate residue of their poly A stretches and translocation of the capacitated messengers to the cytosol via a RNP-membrane complex is proposed as a trigger of embryonic differentiation.