EsMlp, a Muscle-LIM Protein Gene, Is Up-regulated during Cold Exposure in the Freeze-Avoiding Larvae of Epiblema scudderiana

Abstract

Screening of a cDNA library identified transcripts that were up-regulated by cold (4 or −20°C) exposure in larvae of the freeze-avoiding goldenrod gall moth, Epiblema scudderiana. One clone contained a full-length open reading frame encoding a protein of 94 amino acids. The gene product, with 79.1% of residues identical with the Drosophila LIM protein Mlp60A, was named EsMlp and contained a single LIM domain and consensus sequences characteristic of a LIM protein. Transcript levels rose approx twofold when larvae were shifted from 4 to −20°C and approx threefold over the midwinter months compared with larvae sampled in October or April. EsMlp expression was high in larval head (possibly due to expression in pharyngeal muscles) and body wall but was not detected in fat body. Immunoblotting revealed a three- to fourfold increase in EsMlp protein in midwinter larvae (January-February) compared with November-collected animals and a further rise to eightfold higher than November values in larvae collected in April. Cold up-regulation of EsMlp and the pattern of EsMlp levels in the larvae suggest possible roles for the protein, such as in muscle maintenance over the winter or as a preparative function that could facilitate the rapid resumption of development and metamorphosis when environmental temperatures rise in the spring.