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). The strong suppression of the mir-71(lf) defect by hbl-1(RNAi), and the relatively weak effect of miR-71 on hbl-1 expression, are consistent with the idea that miR-71 exerts its role by modulating activities of multiple genes related to hbl-1 function in developmental timing. 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.

S1A indicated a dominant role of intestinal miRNAs in regulating L1 starvation survival. We used a dual-color 3′UTR reporter system revery play login (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.

{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.}