Defects in the C. elegans acyl-CoA Synthase, acs-3, and Nuclear Hormone Receptor, nhr-25, Cause Sensitivity to Distinct, but Overlapping Stresses

Abstract

Metazoan transcription factors control distinct networks of genes in specific tissues, yet understanding how these networks are integrated into physiology, development, and homeostasis remains challenging. Inactivation of the nuclear hormone receptor nhr-25 ameliorates developmental and metabolic phenotypes associated with loss of function of an acyl-CoA synthetase gene, acs-3. ACS-3 activity prevents aberrantly high NHR-25 activity. Here, we investigated this relationship further by examining gene expression patterns following acs-3 and nhr-25 inactivation. Unexpectedly, we found that the acs-3 mutation or nhr-25 RNAi resulted in similar transcriptomes with enrichment in innate immunity and stress response gene expression. Mutants of either gene exhibited distinct sensitivities to pathogens and environmental stresses. Only nhr-25 was required for wild-type levels of resistance to the bacterial pathogen P. aeruginosa and only acs-3 was required for wild-type levels of resistance to osmotic stress and the oxidative stress generator, juglone. Inactivation of either acs-3 or nhr-25 compromised lifespan and resistance to the fungal pathogen D. coniospora. Double mutants exhibited more severe defects in the lifespan and P. aeruginosa assays, but were similar to the single mutants in other assays. Finally, acs-3 mutants displayed defects in their epidermal surface barrier, potentially accounting for the observed sensitivities. Together, these data indicate that inactivation of either acs-3 or nhr-25 causes stress sensitivity and increased expression of innate immunity/stress genes, most likely by different mechanisms. Elevated expression of these immune/stress genes appears to abrogate the transcriptional signatures relevant to metabolism and development.

Measuring Oxidative Stress Resistance of <em>Caenorhabditis elegans</em> in 96-well Microtiter Plates

“…elegans is an attractive model organism to study genetically oxidative stress resistance in vivo since it can be easily cultured, and rapidly leads to a large number of genetically identical offspring. Multiple methods to measure oxidative stress resistance have been previously described and they are based on the supplementation of culture plates with various ROS sources such as PQ, rotenone, H 2 O 2 , and juglone 25,26,[29][30][31][32] . Here we describe a protocol that measures oxidative stress resistance in liquid in 96 well plates using 100 mM PQ.…”

The receptor tyrosine kinase HIR-1 coordinates HIF-independent responses to hypoxia and extracellular matrix injury

“…S3B). Further more, direct permeability assays with the cuticle impermeable dye Hoechst 22358 (38) revealed nuclear intercalation of the dye only in perl-1 and dpy3 mutants, let-268 knockdowns, and hypoxia treated WT animals but not WT ani mals under normoxia ( fig. S3, C and D).…”

Modulatory upregulation of an insulin peptide gene by different pathogens in C. elegans

“…It also identified a number of other categories previously noted to be enriched for innate immune genes. This includes genes regulated by nhr-25 and acs-3 37 , sam-10 38 or dapk-1 39 , induced by infection with Burkholderia pseudomallei 40 and in a series of mutants with an alteration of their cuticle and/or osmotic balance (osm-7, osm-8, osm-11) 41 . As expected, there was also a very significant enrichment (p < 10 -28 ) for genes characterized as being expressed in the epidermis 42 (Table S1).…”