We further examined worms recovering from 4 d of L1 starvation and found that around 90% of the mir-71(lf) mutants displayed retarded vulval precursor cell (VPC) division, compared with less than 5% in wild type (Fig. 4A). In contrast, the nuclear-localized GFP expression under the control of the 3′UTR of age-1(Fig. 3 C and D) or unc-31 (Fig. 3 E and F) was strongly repressed in the control worms, but prominently derepressed in mir-71(lf) mutant worms. If the 3′UTR of age-1 or unc-31 is repressed by miR-71, the GFP expression will be repressed in tissues where miR-71 is expressed in wild-type worms, but derepressed in the same tissues of mir-71(lf) worms. Among short-lived miRNA mutants, a mir-71 deletion mutant, mir-71(n4115) (referred to as mir-71(lf) hereafter), displayed a severe reduction in L1 starvation survival rate (Table S1 and Fig. 2A).
We further found that this survival rate reduction of ain-1 mutants was overcome by ectopic expression of the AIN-2 protein in the intestine but not in the muscle (Fig. 1A and Fig. S1A). In this study, we addressed the questions of whether and how miRNAs impact developmental arrest and the long-term survival of early L1 stage worms in response to food starvation. Furthermore, a recent study suggests that the expression of certain miRNAs is differentially regulated by starvation-induced dauer diapause (15). Consistent with these ideas, several recent lines of evidence suggest that miRNA let-7 and the heterochronic genes lin-42 and hbl-1 are required to regulate the starvation-induced dauer diapause (10–12) and that a number of miRNAs including lin-4 and mir-71 are involved in regulating life span (13, 14).

• We found that the mRNA level of UNC-31 was up-regulated by about 20% in mir-71(lf) (Fig. 3A).
• One who loves spending time with their family during the holidays and cooking delicious meals, despite the stress it sometimes brings on.
• The 8 months of “field research” that I engaged in after 1.5 years of sobriety in led me to the familiar line, “how did I get here (again)”.
• However, the mechanisms that coordinate the long-term survival, overall developmental arrest, and reinitiation remain to be investigated.
• The nematode Caenorhabditis elegans responds to starvation by entering developmental arrest at multiple stages of its life cycle (1).
• We speculate that the expression of heterochronic genes controlling the L2/L3 programs, including that of hbl-1 and lin-42, are increased during L1 diapause to arrest the developmental progression, and miR-71 is probably required to suppress these “excess” signals during the recovery phase (Fig. S5).
• To determine viability, 20-μL aliquots (60–100 worms) were placed every 3 d onto two 6-cm nematode growth medium (NGM) plates seeded with OP50, and the numbers of L1 worms were recorded as number of plated worms (Np).

Briefly, worms were well fed for at least two generations, and gravid adults were bleached with hypochlorite and sodium hydroxide. L1 starvation assay was adapted from a previously described protocol (3). Worms strains were grown and maintained at 20 °C as described (29). This result is consistent with the observation that miR-71 is specifically required for the starvation-induced stress response (Fig. S5). For example, we observed a robust retarded mutant phenotype in the vulval lineage but did not see obvious defects in seam cell differentiation or alae formation. Our data provide the experimental evidence that two components of the InsR pathway are likely direct targets of miR-71 in its role in a specific physiological process, L1 diapause (see a model in Fig. S5).

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{In contrast, the mir-71(lf) mutant worms recovering on hbl-1(RNAi) displayed precocious VPC divisions similar to that seen in wild type (Fig. 4E). Consistent with the observation described above, the 4-d–starved mir-71(lf) mutants recovering on the RNAi control plates displayed the highly penetrant retarded defect in VPC division. (D) Bar graph showing that the delayed VPC timing defect of mir-71(lf) worms was enhanced by daf-16(lf) after 1 or 3 d of L1 starvation.}