DNA-dependent RNA polymerases from Artemia salina. IV. appearance of nuclear RNA polymerase activity during pre-emergence development of encysted embryos.

Dessicated and encysted gastrulae of the brine shrimp Artemia salina remain metabolically dormant until they are rehydrated. At this time development resumes, culminating in the hatching of free swimming nauplius larvae. The resumption of embryogenesis provides a convenient system for studying biochemical events which accompany development of a eukaryotic organism, and in particular Artemia has proven useful for studies of the transcriptional regulation of gene expression. Encysted gastrulae of Artemia yielded only trace amounts of DNA-dependent RNA polymerase activity when crude nuclear pellets were subjected to sonication at high ionic strength. Furthermore, when crude nuclear pellets from encysted gastrulae and developing nauplius larvae were mixed prior to sonication, subsequent solubilization of proteins from the mixture did not yield RNA polymerase activity; sonication of the pellet from nauplii alone resulted in the solubilization of large quantities of RNA polymerases I and II as we have previously found [1]. RNA polymerases I and II were detectable in sonicates of crude nuclear pellets after 1-h incubation of Artemia cysts in sea water. This presents the possibility that dormant gastrulae of the brine shrimp contain RNA polymerase which is inactive, and that the rapid appearance of nuclear enzymatic activity which accompanies the resumption of development may not require de novo synthesis of the polymerase.