(A) Representative images of hsp-6::GFP expression in wild-type, mter-4R178E,K262E,K263E, mtg-1R171E,K178E,K180E, nsun-4M225A,K226A, catalytic dead nsun-4C90A, and nsun-4M225A,K226A,L286Y,A287Y mutant animals. The matched wild-type control for nsun-4M225A,K226A,L286Y,A287Y resembles the shown wild-type, and is omitted for simplicity. White arrows in mtg-1 mutants represent homozygous mutant animals based on the absence of umnIs21 reporter expression from balancer chromosome. All animals express the zcIs13 [hsp-6::GFP] reporter which is specifically expressed in response to mitochondrial stress. Animals were grown for 72 hr at 22.5°C. Scale bars=200 µm. (B) Top five GO-terms based on p-value from g:Profiler analysis of genes upregulated greater than 0.5 (log2) in mter-4R178E,K262E,K263E mutants when compared to wild-type animals. (C) Venn diagram comparison of genes upregulated in mter-4R178E,K262E,K263E, isp-1(qmv150), and nuo-6(qm200) mutants. isp-1 and nuo-6 gene expression data from Yee et al., 2014. (D) Fraction of wild-type and mter-4R178E,K262E,K263E mutants sterile at 22.5°C. n=100 animals. (E) Fraction of wild-type and mter-4R178E,K262E,K263E mutants at different developmental stages after 48 hr at 22.5°C. n=200 animals. GO, gene ontology.