| The novel factor PEB-1 was identified through its ability to bind an enhancer element of the pharyngeal-specific myo-2 gene. To determine PEB-1's role during pharyngeal development I characterized peb-1's expression pattern, misexpressed it outside the pharynx, and examined effects of loss-of-peb-1 function on C. elegans development.; Analysis of peb-1 expression indicates it is expressed throughout C. elegans development. The PEB-1 transcript is most abundant in embryos and early larvae, decreases in later larval stages, and is mostly expressed in the germ line in adults. PEB-1 protein is expressed in a temporal pattern consistent with that of mRNA and is detected in numerous C. elegans tissues. In early larvae, extensive analysis reveals that PEB-1 is expressed in most, if not all, non-neuronal nuclei in the pharynx, hypodermis, and hindgut. The most striking common feature of PEB-1-expressing cells in these tissues is that their apical surfaces all contact cuticle.; Ectopic production of PEB-1 protein is not sufficient to activate expression of MYO-2 protein or C183-regulated reporters. Co-ectopic expression of PEB-1 and PHA-4 in the same cells also does not cause ectopic expression of these markers, suggesting a model in which PEB-1 may negatively modulate PHA-4's ability to activate transcription through C183.; Reduction of peb-1 function by RNAi results in morphological defects in the somatic tissues in which peb-1 is expressed. Larvae grew slowly and exhibited a thin, pale appearance. Although the g1 pharyngeal gland cell processes were grossly swollen in many animals, the pharynx appeared normal in most respects.; Characterization of a recessive peb-1 deletion allele (cu9), which is likely null, shows that peb-1 is necessary for C. elegans development. peb-1(cu9) homozygotes arrest as larvae and display many phenotypes seen in RNAi, although they are generally more severe. In addition, peb-1(cu9) homozygotes arrest with a stuffed pharynx and/or undegraded cuticle in the pharyngeal lumen, indicating the pharynx is unable to adequately function. Careful analyses of these phenotypes, as well as comparison with molting-defective lrp-1(ku156) larvae, suggest that the most prominent defect in peb-1(cu9) animals is an inability of the pharynx to adequately degrade old cuticle during molting. |
