Identification of molecular mechanisms underlying developmental decision of Caenorhabditis elegans

Abstract

Animals adapt to ever-changing environmental conditions to regulate their development. Our goal is to understand the mechanisms by which environmental signals are transduced and integrated with internal status to regulate development. The free-living nematode Caenorhabditis elegans undergoes reproductive development from egg to adult through four larval stages (L1-L4) in favorable environments. When L1 animals exposed to unfavorable environments, animals fail to initiate reproductive development and are arrested as stress-resistant and long-lived larva at dauer diapause, which is an alternative third developmental stage. However, how young animals make this developmental decision depending on environmental conditions at the time is not fully elucidated. To address this question, we first searched for genes of which expression pattern is altered at dauer diapause. Previous genetic studies have demonstrated that flp-8 or flp-4 FMRFamide-related peptide genes are differentially expressed in all touch receptor neurons of the dauer stage (Kim and Li, 2004). To identify the regulatory mechanism of flp gene expression, we first analyzed the flp gene promoter and found the putative cis-regulatory elements essential for expression in touch receptor neurons. We next found that expression of flp-8 in touch receptor neurons are regulated by MEC-3 and UNC-86, which are the transcription factors required for production and differentiation of the touch receptor neurons. To investigate whether this flp gene expression is regulated by the genes which are dauer-specific or involved in epigenetic mechanisms, we tested several candidate genes but none of animals carrying mutations in the genes displayed modified expression pattern both in non-dauer and dauer animals. Thus, our results suggest that unidentified genes or signaling pathways are likely to modify the expression of flp genes during dauer diapause, and that future genetic screen by mutagenesis may allow us to identify the nature of the genes or pathways. ⓒ 2016 DGIST