Olmedo, Maria et al. (2015) International Worm Meeting "Dissection of the temperature control of C. elegans larval development using a novel high-throughput method."

Geibel, Mirjam, Merrow, Martha, Olmedo, Maria, Artal-Sanz, Marta

[International Worm Meeting, 2015]

C. elegans postembryonic development is characterised by four discrete larval stages. The transitions between larval stages entail a series of events including the formation of a new cuticle and escape from the old one, cessation of pharyngeal pumping and behavioral quiescence. The entire process is called molting and robust waves of gene expression cycle with these processes. These events are used as hallmarks to study the timing of the developmental process, typically, by visual inspection. This method is time consuming and unsuitable for screening large numbers of animals.We have applied a method based on bioluminescence to measure the alternation of larval stages and molts, extracting information about the duration of each stage of development. We have validated this method with a lin-42 mutant that shows slower development than wild-type animals (1) and with a daf-2 mutant that shows an extended second larval stage (2).Development in C. elegans is controlled by genetic and environmental factors. Temperature regulates the speed of embryonic and post-embryonic development in many ectothermic organisms. The effect of temperature on embryonic development in C. elegans and Drosophila (3, 4), and on postembryonic development in Drosophila (3) have been described. However, a detailed analysis of larval developmental at different temperatures has never been shown for C. elegans. We have determined the duration of each molt and each larval stage at temperatures between 10.3 C and 27.5 C. The speed of development increases with temperature in a non-linear manner. At low temperatures, the duration of development follows the Arrhenius equation. At higher temperatures, the speed of development deviates from Arrhenius. Furthermore, we have show that this difference stems mainly from the molts. We are currently investigating the implication of thermosensory pathways in the control of developmental speed.1. Monsalve, Van Buskirk and Frand, Current Biology 21, 2033-2045 (2011).2. Ruaud, Katic and Bessereau, Genetics 187, 337-343 (2011).3. Powsner, Physiological Zoology 8, 474-520 (1935).4. Begasse, et al., Cell Reports 10, 647-653 (2015).

Mata-Cabana, Alejandro et al. (2021) International Worm Meeting "Differential regulation of developmental stages supports a linear model for C. elegans postembryonic development."

Piubeli, Francine Amaral, Romero-Exposito, Francisco Javier, Olmedo, Maria, Merrow, Martha, Mata-Cabana, Alejandro, Geibel, Mirjam

[International Worm Meeting, 2021]

During C. elegans postembryonic development, each of the four larval stages entails a process of feeding, a period of quiescence, and ecdysis. The repetitive nature of this process resembles oscillatory process as circadian rhythms. Nevertheless, each larval stage has a defined duration and entails specific events. A central question remains as to whether the overall speed of postembryonic development is controlled by a timer that affects all larval stages equally, as opposed to a linear process, where progression of development is achieved by the completion of stage specific events. The perturbation of a regulator of developmental timing would yield slower or faster animals, with larval stages that scale proportionally to the duration of total development. Contrarily, if development proceeds in a linear manner, based on completing stage-specific events, perturbations that affect overall duration of development might have different impact on different stages, depending on the specific events that take place during each stage. The answer to this question calls for precise quantification of postembryonic development in response to varied perturbations that alter overall developmental timing. We have measured the duration of each stage of larval development for over 2,500 larvae, upon perturbations in temperature, in food quantity and quality, and amount of insulin signaling. Importantly, the assay we used monitors development continuously, with a time resolution of five minutes, and resolves the transitions between molts and intermolts. We observed that interventions that alter developmental timing have a differential effect on the discrete stages of larval development. Furthermore, our high-resolution measurement of the effect of temperature has unveiled characteristic features of temperature dependence in C. elegans postembryonic development. Altogether, our results support a mechanism based on a linear progression of postembryonic development, where the events that take place in each stage are differentially impacted by environmental perturbations.

Olmedo, M. et al. (2017) International Worm Meeting "Larval density during L1 arrest impacts recovery from starvation through changes in DAF-16 nuclear localization."

Olmedo, M., Artal-Sanz, M., Cerero, L., Mata-Cabana, A., Merrow, M., Fernandez-Yanez, A., Rodriguez-Palero, M. J.

[International Worm Meeting, 2017]

The developmental progression of Caenorhabditis elegans can be slowed down or interrupted when animals face unfavourable conditions like food scarcity. C. elegans larvae arrest as L1s when hatching in the absence of food. Arrested L1s can survive several weeks without food and present increased resistance to stress. Several genetic and environmental factors impact the survival of arrested L1s. These include the Insulin/insulin-like growth factor signalling (IIS) pathway and larval density during arrest 1,2. The effect of density is mediated by exposure of unknown compounds secreted after hatching 2. When food becomes available, larvae resume postembryonic development but animals that have been starved for long periods of time take longer to reach adulthood 3. This effect of starvation was attributed to a developmental delay after extended starvation. However, using a method we developed to measure developmental timing 4 we have been able to measure the duration of each stage of development after extended starvation. We have observed that developmental speed is resilient to time in starvation. The later entry into adulthood after extended arrest corresponds, instead, with a delay to resume development. That is, extended starvation increases recovery time. Using the same method, we observe that recovery time is affected by interventions that affect survival to starvation, like mutations in the IIS pathway and density of animals during arrest. In addition, we show that high density of animals contributes to the maintenance of DAF-16 nuclear localization during arrest, contributing to longer survival and fast recovery from arrest. Our results indicate that density and low insulin signalling impact DAF-16 function in a similar manner, possibly allowing integration of the two signals to control developmental arrest. 1. Baugh, L. R. To Grow or Not to Grow: Nutritional Control of Development During Caenorhabditis elegans L1 Arrest. Genetics 194, (2013). 2. Artyukhin, A. B., Schroeder, F. C. & Avery, L. Density dependence in Caenorhabditis larval starvation. (2013). 3. Lee, I., Hendrix, A., Kim, J., Yoshimoto, J. & You, Y.-J. Metabolic Rate Regulates L1 Longevity in C. elegans. (2012). 4. Olmedo, M., Geibel, M., Artal-Sanz, M. & Merrow, M. A High-Throughput Method for the Analysis of Larval Developmental Phenotypes in Caenorhabditis elegans. Genetics (2015).