Cycloheximide-resistant ribosomes reveal adaptive translation dynamics in C. elegans.

Protein translation regulation is critical for cellular responses and development, yet how elongation stage disruptions shape these processes remains incompletely understood. Here, we identify a single amino acid substitution (P55Q) in the ribosomal protein RPL-36A of Caenorhabditis elegans that confers complete resistance to the elongation inhibitor cycloheximide (CHX). Heterozygous animals carrying both wild-type RPL-36A and RPL-36A(P55Q) develop normally but show intermediate CHX resistance, indicating a partial dominant effect. Leveraging RPL-36A(P55Q) as a single-copy positive selection marker for CRISPR-based genome editing, we introduced targeted modifications into multiple ribosomal protein genes, confirming its broad utility for altering essential loci. In L4-stage heterozygotes, where CHX-sensitive and CHX-resistant ribosomes coexist, ribosome profiling revealed increased start-codon occupancy, reduced disome formation, and no codon-specific pausing. Surprisingly, chronic CHX treatment did not activate canonical stress pathways (ribosome quality control, integrated stress response, and ribotoxic stress response), as indicated by the absence of RPS-10 ubiquitination, eIF2α or PMK-1 phosphorylation, or ATF-4 induction. Instead, RNA-normalized ribosome footprints revealed selective changes in translation efficiency (TE), with reduced nucleolar/P-granule components and increased oocyte development genes. Consistently, premature oocyte development was observed in L4 animals. These findings suggest that partial inhibition of translation elongation disrupts developmental timing across tissues, likely by altering TE.