Thioredoxins are a large family of proteins that catalyze thiol-disulfide redox reactions to regulate many cellular processes, one of them being stress resistance. The C. elegans gene
trx-1 encodes a thioredoxin that is expressed in the ASJ ciliated chemosensory neurons. We have previously shown that
trx-1 deletion mutants are short-lived, whereas animals expressing a translational
trx-1::gfp fusion transgene are long-lived relative to wild type (WT). We report here that TRX-1 participates in ASJ-dependent starvation stress responses. We find that
trx-1::gfp expression in ASJ neurons is up-regulated in WT animals under conditions of starvation and in the developmentally arrested dauer larval stage, implicating
trx-1 in ASJ-dependent stress resistance mechanisms. Interestingly, in
daf-11 guanylyl cyclase mutants,
trx-1::gfp expression in ASJ neurons is constitutively up-regulated, indicating that depletion of cGMP up-regulates
trx-1 expression in ASJ. Similarly, deletion of
trx-1 alters the dauer formation constitutive (Daf-c) phenotype of
daf-11 mutants, supporting the involvement of
trx-1 in ASJ-dependent starvation stress responses (e.g., dauer arrest). In addition, we observe that deletion of
trx-1 partially suppresses the Daf-c phenotype of
daf-28 insulin-like mutants, suggesting that TRX-1 affects the insulin/IGF-like signalling (IIS) pathway in ASJ neurons to promote dauer arrest. In relation to our findings, it has previously been demonstrated that when C. elegans suffers through periods of starvation, the DAF-16 FOXO transcription factor, which acts downstream of the IIS pathway, promotes survival (e.g., longevity and dauer formation) by regulating the expression of stress response genes. Taken together, it seems likely that the up-regulation of
trx-1 under conditions of starvation, forms part of a stress response elicited to protect C. elegans in harsh food-deprived environments. As a consequence, this ASJ-dependent stress response would promote longevity and dauer formation at the cost of reproduction and growth. Current efforts are directed towards studying the genetic interactions of
trx-1 with genes involved in the aging and dauer pathways, to identify the upstream regulators of
trx-1 expression. These studies will help us understand the functions of
trx-1 in the ASJ-dependent stress responses.