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

In worms that recovered from 4 d of L1 starvation, we also found that a significant portion of the mir-71(lf) mutants displayed egg-laying defects and overproliferating or precociously reflexed gonads. 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). We found that the 3′UTRs of several genes of the InsR pathway, including unc-31, age-1, pdk-1, akt-2, and sgk-1, contain predicted miR-71 targeting sites (as predicted by TargetScan and mirWIP). (H and I) Fluorescence images (H) and statistical data (I) showing that the M cell diveded in fed animals but remained undivided in 4-, 7-, or 11-d–starved L1 wild-type and mir-71(lf) worms. (E) Fluorescence and DIC images showing that the unc-31 3′UTR reporter was repressed in mir-71(+)worms (2/2 transgenic lines) but not in mir-71(lf) worms (4/4 transgenic lines). We found that the poor survival rate of daf-16(mu86)(lf) was further decreased by mir-71(lf) (Fig. 2C), consistent with the notion that a portion of miR-71 activities regulate genes that act in parallel to UNC-31–mediated InsR/PI3K signaling for long-term survival during L1 diapause.
We thus asked whether miR-71 was required for the reinitiation of developmental programs during the recovery phase after L1 starvation. These results suggest that miR-71 regulates the expression of unc-31 and age-1 through their 3′UTRs. Note that there are extra GFP-positive cells (red arrows) in mir-71(lf) mutants.
On the other hand, the role of a particular miRNA (miR-71) is executed by repressing the expression of many genes in multiple pathways. On one hand, we showed that deletions of a good number of miRNAs have varying impacts on the L1 diapause survival rate, although they may effect the rate through different mechanisms. 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. We found that the known developmental timing genes, hbl-1, lin-42, and lit-1, were at the top of the list (TargetScan). To understand how miR-71 affects VPC division, we searched its predicted targets for potential genes involved in regulating developmental timing. These results indicate that miR-71 plays a significant role in larval development of animals recovering from L1 diapause and likely does so by regulating the expression of components of the insulin receptor/DAF-16 pathway, as well as factors acting downstream, or in parallel to, DAF-16.
If you become locked out of those services and don’t have a backup of your accounts in Duo Mobile, you’ll need to contact the support team for that application (or perform the account recovery process for each of those third-party applications). However, whether an account can be restored depends upon Duo Restore being enabled by the administrator in the Duo Admin Panel or whether you’ve set a recovery password for reconnecting third-party accounts. 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). Knocking down lit-1 by RNAi in mir-71(lf); lin-42(lf) double mutants caused no significant suppression of the VPC timing defects of mir-71(lf) worms. To determine the functional relationship of miR-71 with LIN-42 and LIT-1, mir-71(lf); lin-42(lf) L1 worms were starved for 4 d and recovered on lit-1(RNAi) plates. We then compared the expression of a hbl-1 3′UTR reporter (18) in the mir-71(lf) mutants with that in wild type and found that the expression of this reporter was slightly derepressed at L3 in the mir-71 mutant (Fig. 4 F and G).

  • S1A indicated a dominant role of intestinal miRNAs in regulating L1 starvation survival.
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  • We found that the poor survival rate of daf-16(mu86)(lf) was further decreased by mir-71(lf) (Fig. 2C), consistent with the notion that a portion of miR-71 activities regulate genes that act in parallel to UNC-31–mediated InsR/PI3K signaling for long-term survival during L1 diapause.
  • (B) Bar graph showing the correlation between the severity of the retarded vulval precursor cell (VPC) timing defect of mir-71(lf) mutants and the duration of L1 starvation.

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