Meeting Abstract

87.7  Monday, Jan. 6 11:30  Differential expression influences different body plan development in chordates ascidians LOWE, E.K.*; BROWN, C.T.; SWALLA, B.J.; CHRISTIAEN, L.A.; STOLFI, A.; Michigan State University; Michigan State university; University of Washington; New York University; New York University elijahlowe@gmail.com

Molgula occulta and Molgula oculata are two closely related chordate ascidians that are almost indistinguishable in their adult stages. However, they have drastically different larval phenotypes. During the embryonic stage, only M. oculata forms a post-anal tail containing a notochord—a group of cells organized in a rod shaped structure and one of the key features of the chordate phylum. In contrast, M. occulta is one of several species of Molgula to lose this feature. Hybrids, with a partially formed tail, have been produced through the cross fertilization of these two species, the only Molgula species known to hybridize. Using Next Generation Sequencing technology, we sequenced the embryonic transcriptomes of the two species and their hybrids at three developmental stages to study the mechanisms behind tail loss in M. occulta. A first look at genes associated with notochord development has shown most genes to be present and expressed during embryogenesis of both species. When analyzing differential expression patterns in the two species and the hybrid a shift in gene expression occurs starting at neurulation. This pattern shows genes being up-regulated in M. oculata and the hybrid, while begin down-regulated in M. occulta. The expression of these genes may be the key to the lack of tail development in M. occulta. In addition to the transcriptomes, we recently assembled the genomes for M. occulta, M. oculata, and another tailed molgulid, M. occidentalis. This study allows us to analyze tail loss in greater depth than previously done.