Fig. 4.

3′UTRs during development. (A) C. elegans developmental transitions: embryogenesis, four larval stages, and adults. In unfavorable environments, L1 larvae arrest in dauer stage and can re-enter the life cycle as L4 larvae. herm, hermaphrodites. (B) The number of 3′UTR isoforms per gene decreases significantly during development (blue) (*p ∼ 0.004, permutation test). The average length of 3′UTRs decreases during development (red). Adult males have shorter average 3′UTRs than hermaphrodites. Embryos show more stage-specific 3′UTR isoforms for genes expressed during multiple developmental stages (green) (see table S8). (C) Proportion of genes showing stage-specific expression of alternative 3′UTR isoforms (see table S9). Embryos and dauers favor longer 3′UTR isoforms. (D) Differential 3′UTR-isoform expression during development (ubc-18 shown; see data sets S5 and S6 for details). The bar chart illustrates the relative abundance of short versus long 3′UTR isoforms for ubc-18 in each stage (sum per stage = 100%, left y axis). The line graph shows the relative abundance across all stages (sum per gene across all stages = 100%, right y axis). Green bars highlight differences in 3′UTR isoform usage in the embryo-to-L1 transition and between adult hermaphrodite and male stages. Green arrows indicate dauer entry and exit transitions.