Figure 5. HMR-1 pS1212 Is Required for Interaction between HMP-2 and HMR-1 (A and B) Differential interference contrast (DIC) (A) and confocal (B) images of 1.5-fold elongating
hmr-1(
zu389) homozygotes rescued to viability by HMR1::GFP. Lethality in offspring of
hmr-1(
zu389);
hmr-1::gfp mothers is 85.2% (n = 209). Signal localizes to epidermal AJs similarly to HMR-1 immunostaining (not shown). Scale bar, 10 um. (C and D) The phospho null construct HMR-1(S1212A)::GFP localizes to junctions but is unable to rescue
hmr-1(
zu389) homozygotes to viability (C, DIC; D, confocal). Lethality in offspring of
hmr-1(
zu389)/+;
hmr-1(S1212A)::gfp mothers is 27.4% (n = 1072). Cells in (D) appear compressed due to retraction of the hypodermis subsequent to failure of epiboly. (E and F) HMR-1(T1215A, S1218A)::GFP localizes to junctions and rescues
hmr-1(
zu389) embryonic enclosure and elongation. The
hmr-1 transgene reduces embryonic lethality of
hmr-1(
zu389)/+ offspring from 24.9% (n = 1101) to 16.9% (n = 1,055, three independent lines). Pictured is a representative offspring from a
hmr-1(
zu389)/+;
hmr-1(T1215A, S1218A)::gfp mother (E, DIC; F, confocal). (G and H) Wild-type HMP-2::GFP localizes to junctions (H) and rescues
hmp-2(
zu364) to viability (G). (I)
hmp-2(
zu364) homozygotes fail to elongate and die with the Humpback phenotype. The
zu364 lesion was identified as a point mutation resulting in HMP-2 R271C. (J) HMP-2(R271C)::GFP localizes exclusively to the cytoplasm, and embryos die with the Hmp phenotype, consistent with a model in which this residue is crucial for interacting with HMR-1 pS1212. Arrowhead indicates dorsal humps.