microRNAs play critical roles in the survival and recovery of Caenorhabditis elegans from starvation-induced L1 diapause

Abstract

Environmental stresses and nutrition availability critically affect animal development. Numerous animal species across multiple phyla enter developmental arrest for long-term survival in unfavorable environments and resume development upon stress removal. Here we show that compromising overall microRNA (miRNA) functions or mutating certain individual miRNAs impairs the longterm survival of nematodes during starvation-induced L1 diapause. We provide evidence that miRNA miR-71 is not required for the animals' entry into L1 diapause, but plays a critical role in long-term survival by repressing the expression of insulin receptor/PI3K pathway genes and genes acting downstream or in parallel to the pathway. Furthermore, miR-71 plays a prominent role in developmental recovery from L1 diapause partly through repressing the expression of certain heterochronic genes. The presented results indicate that interactions between multiple miRNAs and likely a large number of their mRNA targets in multiple pathways regulate the response to starvation-induced L1 diapause.F ood deprivation is a life-threatening challenge that animals frequently face as individuals and as species. Different organisms have developed versatile growth arrest strategies to overcome starvation-induced metabolic and developmental problems. The coordinated entrance into developmental arrest, long-term survival, and the reinitiation of development upon food availability are important biological processes to investigate.The nematode Caenorhabditis elegans responds to starvation by entering developmental arrest at multiple stages of its life cycle (1). When late, first larval stage (L1) worms sense unfavorable conditions, they enter an alternative and long-lived larval stage called dauer larvae (or dauer diapause). However, when newly hatched L1 worms encounter an environment with no food, developmental programs arrest and the worm enters L1 diapause. Unlike dauer diapause, L1 diapause is not accompanied by life cycle changes and has not been shown to require certain signaling pathways that control the formation of dauer diapause [such as TGF-β signaling (daf-1, daf-7) and nuclear hormone receptor (daf-12)] (2, 3). Furthermore, worms that are long-lived due to dietary restriction or decreased mitochondrial respiratory rates are short-lived during L1 diapause, suggesting that the mechanisms controlling L1 starvation survival are different at least in some aspects from those controlling aging (3).Previous studies showed that the release of postdocking calciumregulated dense-core vesicles, the insulin receptor (InsR) pathway, the AMPK pathway, and protein chaperones are required for the long-term survival of starved L1 worms (2-4). The roles of InsRs have also been implicated in arresting the cell cycle in germ cells and a portion of somatic cells during L1 diapause (2, 4). Upon entering L1 diapause, RNA polymerase II quickly accumulates and pauses at promoter regions, and this accumulation was speculated to stop transcription and facilitate the immediate reinit...

Long live FOXO: unraveling the role of FOXO proteins in aging and longevity

“…The importance of DAF‐18/PTEN tumor suppressor in longevity and dauer larva formation, through the regulation of the IIS pathway, has been established in the late 1990s by several research groups (Ogg & Ruvkun, 1998; Gil et al ., 1999; Mihaylova et al ., 1999; Rouault et al ., 1999). DAF‐18/PTEN has been shown to regulate L1 arrest in the germ line, and insulin‐like signaling appears to be transduced by AGE‐1/PI3K during L1 arrest (Weinkove et al ., 2006; Zhang et al ., 2011b). …”

AMPK blocks starvation-inducible transgenerational defects in Caenorhabditis elegans

“…The L1 starvation assay was adapted from previously described protocols (56,57). Briefly, animals were fed with OP50 for at least five generations before any analysis.…”

To Grow or Not to Grow: Nutritional Control of Development DuringCaenorhabditis elegansL1 Arrest

“…The daf-16 L1 arrest-defective phenotype includes the normal pattern of cell divisions, migrations, and fusions that occur during L1 development, though much slower than normal development of fed larvae. DAF-18/ PTEN regulates L1 arrest in the germline (see Germline arrest), and insulin-like signaling appears to be transduced by AGE-1/PI3K during L1 arrest (Weinkove et al 2006;Zhang et al 2011), but other components of the pathway have not been examined ( Figure 2). Consistent with the pathway having the same structure as in regulation of dauer formation (Hu 2007), daf-16/FOXO is epistatic to daf-2/InsR (Baugh and Sternberg 2006).…”