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). This is consistent with hbl-1 being one of the downstream targets of miR-71, although this modest effect alone is not expected to account for the vulval developmental phenotype in mir-71 mutant. In starved L1 worms, we detected only a slight increase in the mRNA level of hbl-1 in mir-71 mutants compared with that in wild type (∼10%), which may not be biologically significant. 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).
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). A total of 16–24 h later, the density of newly hatched L1 worms was adjusted to three to five worms per microliter S-basal. The eggs were transferred to plates seeded with HB101 and bleached again 3 d later. 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).
(D) Fractions of worms that carry 3′UTR reporter transgene and show no GFP expression GFP(−), weak GFP expression GFP(+/−), and comparable GFP expression to mCherry GFP(+). We found that the mRNA level of UNC-31 was up-regulated by about 20% in mir-71(lf) (Fig. 3A). These results suggest that a significant portion of the miR-71 activities in L1 diapause survival may be devoted to regulating the activities of UNC-31–mediated InsR/PI3K signaling and that the rest of miR-71 activity may regulate UNC-31–independent pathways. We next examined the relationship between miR-71 and UNC-31, which functions upstream of AGE-1 during L1 diapause by regulating calcium-regulated dense-core vesicle fusion and the release of an insulin-like ligand (3). We identified 10 miRNA mutants that showed reduced survival rates with a stringent standard, as well as a few miRNA mutants with slightly increased survival rates (Table S1, Fig. 1D, and Fig. S1B).
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). (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. (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.
Enabling Duo Restore (Legacy)
Compromising overall miRNA function dramatically reduces the survival rate of L1 worms in starvation-induced diapause, and the effect can be significantly suppressed by an age-1/PI3K mutation. Furthermore, miR-71 plays a prominent role in developmental recovery from L1 diapause partly through repressing the expression of certain heterochronic genes. When you restore a backup that contains third-party account information you must enter the recovery password to decrypt the backup. If you opt-in to third-party account backup and restore, and have set an account recovery password, then the app backups to Google Drive (Android) or iCloud (iOS) do include the private key information for your third-party accounts.