Abstract
The free-living soil nematode Caenorhabditis elegans adapts its development to the availability of food. When food is scarce and population density is high, worms enter a developmentally arrested non-feeding diapause stage specialized for long-term survival called the dauer larva. When food becomes available, they exit from the dauer stage, resume growth and reproduction. It has been postulated that compound(s) present in food, referred to as the “food signal”, promote exit from the dauer stage. In this study, we have identified NAD+ as a component of bacterial extract that promotes dauer exit. NAD+, when dissolved in alkaline medium, causes opening of the mouth and ingestion of food. We also show that to initiate exit from the dauer stage in response to NAD+ worms require production of serotonin. Thus, C. elegans can use redox cofactors produced by dietary organisms to sense food.
Highlights
The search for nutritional resources and selection of suitable food from a variety of available sources facilitate the adaptation of an organism to its environment
A quantitative bioassay for the purification of the food signal The bacteria Escherichia coli is routinely used as food for C. elegans in laboratory conditions and it has been shown that dauer larvae exit diapause upon exposure to fresh E. coli in the growth medium [7]
In order to purify and chemically characterize the food signal derived from bacteria, we prepared a methanolic extract from E. coli
Summary
The search for nutritional resources and selection of suitable food from a variety of available sources facilitate the adaptation of an organism to its environment. Organisms evaluate its nutritive quality and decide whether to continue the search or to make use of the already detected food source [1]. The nematode C. elegans is widely used in research related to food detection and the physiological responses to different diets [2, 3]. C. elegans undergoes a fast reproductive life cycle comprised of four larval stages (L1 to L4) that results in the formation of egg-laying adults [5]. The body of dauers are radially shrunk, with a special impermeable cuticle and constricted non-pumping pharynx. If environmental conditions improve and food becomes available, dauers
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