Deviations from temporal scaling support a stage-specific regulation for C. elegans postembryonic development

Abstract

Background After embryonic development, Caenorhabditis elegans progress through for larval stages, each of them finishing with molting. The repetitive nature of C. elegans postembryonic development is considered an oscillatory process, a concept that has gained traction from regulation by a circadian clock gene homologue. Nevertheless, each larval stage has a defined duration and entails specific events. Since the overall duration of development is controlled by numerous factors, we have asked whether different rate-limiting interventions impact all stages equally. Results We have measured the duration of each stage of development for over 2500 larvae, under varied environmental conditions known to alter overall developmental rate. We applied changes in temperature and in the quantity and quality of nutrition and analysed the effect of genetically reduced insulin signalling. Our results show that the distinct developmental stages respond differently to these perturbations. The changes in the duration of specific larval stages seem to depend on stage-specific events. Furthermore, our high-resolution measurement of the effect of temperature on the stage-specific duration of development has unveiled novel features of temperature dependence in C. elegans postembryonic development. Conclusions Altogether, our results show that multiple factors fine tune developmental timing, impacting larval stages independently. Further understanding of the regulation of this process will allow modelling the mechanisms that control developmental timing.

The Egg-Counter: A novel microfluidic platform for characterization ofCaenorhabditis elegansegg-laying

“…When we quantified the time to egg-laying onset (Figure 4B) we found that temperature had a significant impact ( p <.0001), with the mean onset time accelerating from ∼13.2 hours at 15°C to ∼9.9 hours at 20°C ( p <.0001). This result is roughly consistent with the published difference in developmental rate observed for these experimental temperatures, although published developmental-stage-specific deviations in temperature effects may suggest that a strong correlation between observations unexpected 42,62,63 . Regardless of that caveat, the observed difference in onset time demonstrates that the animals were responsive to the experimental temperature regimes.…”

Desynchronization between timers provokes transient arrest duringC. elegansdevelopment

“…4E). This is a remarkable observation, as we have previously observed that the L1 stage is generally less sensitive the interventions that limit developmental rate (6). Indeed, in the context of insulin signaling and all the mutants analyzed previously, we never found a similar impact on L1.…”

“…Analysis of postembryonic development in C. elegans has often relied on observation of morphological changes. Here, we applied a high-throughput, quantitative method to measure development ( 11 ) that allows unveiling unknown complexities on the timing of the different larval stages ( 6 , 12 , 13 ). This method relies on the use of the enzyme Luciferase, which is constitutively expressed in a C. elegans reporter strain ( 11 ).…”

“…Reduced DAF-2 function leads to increased lifespan in a DAF-16 dependent manner, suggesting that this TF is the main effector of the pathway (reviewed in ( 9 )). Hypomorphic daf-2 alleles also show stage-specific developmental delays ( 6 , 8 ). While all larval stages are prolonged in the daf-2(e1370) mutant, the L1 stage shows reduced sensitivity to insulin signaling levels.…”

“…While all larval stages are prolonged in the daf-2(e1370) mutant, the L1 stage shows reduced sensitivity to insulin signaling levels. The delays of the daf-2 mutant have been quantified at the level of molting, but the insensitivity of L1 seems to be due to the specific cell fates of this larval stage ( 6 ). These observations suggest that DAF-2 controls the speed of both the developmental and the molting timer.…”