Worm Breeder's Gazette 10(3): 76
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We are interested in whether dauer larvae are transcriptionally active and if so, whether their pattern of transcription is distinct from other larval stages. As previously reported (WBG 10:1, 74-75), dauer larvae nuclei are indeed active in run-on transcription by RNA polymerase II (RpoI), however, less active than nuclei from other developmental stages. More accurate measurements have demonstrated that the rate of RpoII transcription (relative to nuclear DNA content) is essentially constant for nuclei isolated from all developmental stages except for dauer larvae. In this stage, RpoII transcription is approximately 40% of the level observed for other developmental stages. The rate of RpoII transcription is restored to the level associated with actively growing worms within two hours of placing dauer larvae on food. Transcription of specific genes by dauer larvae was analyzed by allowing nuclei to incorporate [32P]-CTP in a nuclear run-on assay and hybridizing the RNA with dot blots of cloned genes. Dauer nuclei were found to actively transcribe a number (of structural genes including actin, hsp-70 heat shock, ama-1, and collagen in addition to splice leader precursor. However, where was a drastic reduction in transcription of histone and myosin . Since metabolically, dauer larvae are relatively inactive, the question arises of whether transcription observed in isolated nuclei is really a reflection of in vivo patterns as opposed to the in vitro activation of dormant transcription complexes formed before entrance into the dauer stage. To address this question, we compared nuclear transcription with steady-state levels of message in dauer larvae, L3's and recovering dauer larvae (eight hours after return to food). By Northern analysis, equal amounts of heat shock message were found in all three stages; however, actin message was moderately reduced and histone message was completely absent in dauer larvae. The RNA pattern in these stages resemble the transcriptional patterns of nuclei isolated from these stages. This further suggests that dauer larvae are actively transcribing mRNA and that transcription in isolated nuclei is an accurate reflection of what is happening in vivo.