BROWNE, W.E.; SCHMID, B.G.M.; PATEL, N.H.; WIMMER, E.A.; MARTINDALE, M.Q.; Kewalo Marine Lab, University of Hawaii; Institute of Zoology, Georg-August University Goettingen; HHMI, University of California, Berkeley; Institute of Zoology, Georg-August University Goettingen; Kewalo Marine Lab, University of Hawaii: Developmental Expression of otd Genes and Their Role in Patterning the Embryonic Anterior Head, Anterior Brain, and Ventral Midline of Parhyale hawaiensis

The arthropod head is a complex multimeric structure. In insects orthodenticle (otd) plays a significant role in patterning and development of the anterior head ectoderm as well as the protocerebrum, and is also expressed in the ventral midline. Here we present expression patterns associated with two otd orthologs in Parhyale. Ph otd1 is expressed early (pregastrulation) in anterior head ectoderm progenitors and in ventral midline progenitors. As the germband organizes, Ph otd1 is expressed in a bilaterally symmetric, restricted region of the anterior head ectoderm and in the ventral midline cell column. Later in embryonic development, Ph otd1 is expressed throughout the developing protocerebral neuromere. Ph otd2 has a divergent temporal-spatial expression pattern and is not detected until after the head lobes have been organized. During late germband stages Ph otd2 is coincident with the Ph otd1 anterior head expression domain. Ph otd2 is not detected in ventral midline cells until very late in embryonic development. Ph otd1 expression is suggestive of an important role in early patterning of the anterior head ectoderm and the ventral midline and later patterning of the protocerebrum. Ph otd2 expression is inconsistent with a role as a �head gap gene� in patterning of anterior head ectoderm. However, later embryonic expression of Ph otd2 in both the head and midline does suggest some ectodermal/neural patterning function for this gene. Current experiments seek to explore functional roles for both Ph otd1 and Ph otd2 genes in Parhyale.