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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). 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. If this were true, the starved mir-71(lf); daf-16(lf) double-mutant worms should show a slow growth phenotype similar to that of daf-16(lf) worms, but no specific VPC timing defect. (H) Fluorescence and DIC images showing that a lin-42 3′UTR reporter was repressed in mir-71(+) worms (2/2 transgenic lines) and prominently derepressed in mir-71(−) worms (2/2 transgenic lines).

{For examining the age-1 3′UTR reporter, the rol-6(d) marker (100 ng/μl pRF4) was used instead of the unc-119(+) plasmid. Non-Unc stable transgenic lines were maintained, and the expression of GFP and mCherry were observed under a Zeiss Axiovision II microscope. Three days later, the number of worms that were L2 or older was recorded as number of survived worms (Ns), and the survival rate was calculated as Ns/Np, which is an estimation of survived worms in the whole population.}