Both
pe39 and
pe41 enhanced expression specifically in pharyngeal muscles. Transgenic lines bearing
pe39::
pes-10::lacZ and
pe41::
pes-10::lacZ reporters exhibited robust reporter gene expression in the
m3,
m4,
m5, and
m7 pharyngeal muscles, cells that express the endogenous
ceh-22 gene. In addition,the
pe41::
pes-10::lacZ was also expressed in one non muscle cell in the pharynx (provisionally identified as a
g1 gland), the pharyngeal-intestinal valve cells, and a pair of neurons outside the pharynx. The onset of pharyngeal-galactosidase expression was as early as the comma stage of embryogenesis, and expression persisted in the pharyngeal muscles through the remainder of embryogenesis and larval development. Both the spatial and temporal specificity of the
pe39 enhancer in particular was nearly indistinguishable from that of the full-length proximal enhancer.