Planarian flatworms are popular models for the study of regeneration and stem cell biology in vivo. Technical advances and increased availability of genetic information have fueled the discovery of molecules responsible for stem cell pluripotency and regeneration in flatworms. Unfortunately, most of the planarian research performed worldwide utilizes species that are not natural habitants of North America, which limits their availability to newcomer laboratories and impedes their distribution for educational activities. In order to circumvent these limitations and increase the genetic information available for comparative studies, we sequenced the transcriptome of Girardia dorotocephala, a planarian species pandemic and commercially available in North America. A total of 254,802,670 paired sequence reads were obtained from RNA extracted from intact individuals, regenerating fragments, as well as freshly excised auricles of a clonal line of G. dorotocephala (MA-C2), and used for de novo assembly of its transcriptome. The resulting transcriptome draft was validated through functional analysis of genetic markers of stem cells and their progeny in G. dorotocephala. Akin to orthologs in other planarian species, G. dorotocephala Piwi1 (GdPiwi1) was found to be a robust marker of the planarian stem cell population and GdPiwi2 an essential component for stem cell-driven regeneration. Identification of G. dorotocephala homologs of the early stem cell descendent marker PROG-1 revealed a family of lysine-rich proteins expressed during epithelial cell differentiation. Sequences from the MA-C2 transcriptome were found to be 98–99% identical to nucleotide sequences from G. dorotocephala populations with different chromosomal number, demonstrating strong conservation regardless of karyotype evolution. Altogether, this work establishes G. dorotocephala as a viable and accessible option for analysis of gene function in North America.

Motile cilia propel directed cell movements and sweep fluids across the surface of tissues. Orthologs of Dynein Assembly Factor with WD Repeat Domains 1 (DAW1) support normal ciliary beating by enhancing delivery of dynein complexes to axonemal microtubules. DAW1 mutations in vertebrates result in multiple developmental abnormalities and early or prenatal lethality, complicating functional assessment of DAW1 in adult structures. Planarian flatworms maintain cellular homeostasis and regenerate through differentiation of adult pluripotent stem cells, and systemic RNA‐interference (RNAi) can be induced to analyze gene function at any point after birth. A single ortholog of DAW1 was identified in the genome of the planarian Schmidtea mediterranea (Smed‐daw1). Smed‐DAW1 is composed of eight WD repeats, which are 55% identical to the founding member of this protein family (Chlamydomonas reinhardtii ODA16) and 58% identical to human DAW1. Smed‐daw1 is expressed in the planarian epidermis, protonephridial excretory system, and testes, all of which contain cells functionally dependent on motile cilia. Smed‐daw1 RNAi resulted in locomotion defects and edema, which are phenotypes characteristic of multiciliated epidermis and protonephridial dysfunction, respectively. Changes in abundance or length of motile cilia were not observed at the onset of phenotypic manifestations upon Smed‐daw1 RNAi, corroborating with studies showing that DAW‐1 loss of function leads to aberrant movement of motile cilia in other organisms, rather than loss of cilia per se. However, extended RNAi treatments did result in shorter epidermal cilia and decreased abundance of ciliated protonephridia, suggesting that Smed‐daw1 is required for homeostatic maintenance of these structures in flatworms.