Turnover of 32P-phosphate labelled poly(A) RNA during early development of Artemia

The break of dormancy and the early development of Artemia are known to occur in the absence of any DNA and RNA synthesis. The presence and function of preformed messengers in the developing embryos were studied using 32PO4 to track the RNA species that turnover. The rapid labelling of the poly(A) tails of the particulate RNA by 32PO4 is found to be the predominant metabolic event accompanying initiation of development. Although these RNA populations represent a meagre percentage of the total poly(A) RNA of the cells, they nevertheless constitute more than 60% of the labelled poly(A) populations at early stages of development. Moreover the rise in the poly(A) RNA levels of the embryos observed during the first four hours of development could be attributed to the increase in the particulate poly(A) RNA. Prelabelled RNA of this fraction remained rather firmly associated with this fraction in chase experiments, indicating that once processed these RNA species function in association with membranes. The observed shift in the size of these RNAs from low to high molecular weight species further implies that they are being activated to take part in the early developmental programme.