The transcript level of unc-31 was increased in mir-71(lf) worms, compared with that of wild-type controls that were normalized to the value of 1. MiR-71 represses the expression of age-1 and unc-31 through the actions on their 3′UTR, but miR-71 is not required for arresting M cell division during L1 diapause. (B) The severely reduced survival rate of the mir-71(lf) mutant was suppressed by a null allele of unc-31(e928). The effect observed in ain-1(lf) mutants is likely the consequence of the combined effects of attenuating functions of these individual miRNAs. Previous studies indicate that the InsR pathway plays a dominant role in regulating L1 starvation survival and that reducing the activity of the insulin receptor daf-2, the PI3Kinase age-1, or the upstream regulator unc-31 results in increased L1 starvation survival rate (2, 3).
MiR-71 regulates vulval cell division during recovery of starved L1 worms. These results indicate that miR-71 is not essential for arresting seam cell or M-cell divisions during L1 diapause, suggesting that miR-71 function is distinct from DAF-16 function. DAF-16 (the FOXO homolog in C. elegans) has been shown to play an important role in cell cycle arrest and developmental progression partly by promoting cki-1 expression in some somatic cells during L1 arrest (2).
S1A indicated a dominant role of intestinal miRNAs in regulating L1 starvation survival. We used a dual-color 3′UTR reporter system (18) to test the computational, prediction-based hypothesis that the 3′UTRs of age-1 and unc-31 are directly regulated by miR-71 (Fig. 3B and Materials and Methods). Among these potential miRNA targets, the predicted miR-71–targeting sites in the 3′UTRs of age-1 and unc-31 are conserved between C.
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It is possible that other miRNAs, including those in the let-7 family, control developmental timing in other tissues during the recovery phase after L1 starvation. Although the complete removal of miRNA functions causes embryonic lethality or infertility in worms, a partial disruption of overall miRNA functions by mutating either ain-1 or ain-2 provides an effective way to investigate miRNA functions (16, 17). However, we found that the reporter transgene with the lin-42 3′UTR was significantly repressed in wild-type worms, but derepressed in the mir-71(lf) worms (Fig. 4 H and I).
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- DAF-16 (the FOXO homolog in C. elegans) has been shown to play an important role in cell cycle arrest and developmental progression partly by promoting cki-1 expression in some somatic cells during L1 arrest (2).
- To investigate the roles of miRNAs in animal survival during starvation-induced L1 diapause, we impaired the overall miRISC function with loss-of-function (lf) mutants of ain-1 (ku322, ku425, and tm3681) and ain-2(tm2432) and examined their L1 starvation survival rate (Materials and Methods).
- Instead, many specific physiological functions, such as the starvation-induced stress response, are regulated by a miRNA-target network, often involving multiple miRNAs and a large number of their targets.
- MT12993 mir-71(n4115) worms were outcrossed with N2 for four generations before any test except the initial screen.
- Furthermore, a recent study suggests that the expression of certain miRNAs is differentially regulated by starvation-induced dauer diapause (15).
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Biomass recovery was similar across growth strategies, suggesting that growth-related differences play a minimal role in short-term recovery; however, early regrowth was characterised by contrasting trait shifts. Solidago canadensis exhibited high tolerance to heat and drought, with early biomass and trait recovery, indicating potential for dominance under climate extremes. Biomass fully recovered within one month in both growth strategies, but leaf traits showed transient shifts, over-recovery in SLA and under-recovery in LDMC, likely reflecting production of new leaf tissues. Please try again in a few minutes.
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Mutating miR-71 drastically reduces the survival rate of animals in L1 diapause, and the effect can be suppressed by mutations of insulin receptor pathway genes age-1 and unc-31. 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 found that the reduced survival rate of ain-1 was suppressed by either reduction of age-1 function or loss of unc-31 function (Fig. 1 B and C), suggesting that a significant portion of the overall miRNA functions in L1 diapause is upstream of, or in parallel to, the InsR pathway. 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. Here we show that compromising overall microRNA (miRNA) functions or mutating certain individual miRNAs impairs the long-term survival of nematodes during starvation-induced L1 diapause. Third-party accounts will also be restored if third-party backup was enabled on the old device.
- 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.
- Moreover, the expression of hbl-1 is repressed by let-7 family miRNAs at L3 during normal development, and the hyperactivity of hbl-1 caused by failure of miRNA regulation leads to retarded development (26).
- (E) DIC images showing that hbl-1(RNAi) caused precocious VPC divisions in late L2/early L3 in both wild-type and mir-71(lf) worms recovered from 4 d of L1 starvation.
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- Worms strains were grown and maintained at 20 °C as described (29).
- Individual GFP reporter constructs for candidate genes (4 ng/μL) and the mCherry internal control plasmid (4 ng/μL) were mixed with unc-119 rescuing plasmid (20 ng/μL) and pBluescript KS+ (72 ng/μL) and coinjected into unc-119(ed3) and mir-71(n4115); unc-119(ed3) worms following standard protocols (32).
