"The phylogenetic position of dicyemid mesozoans and the genomic changes of adaptation to the parasitic lifestyle”-- Tsai-Ming Lu

Internal Seminar: Tsai-Ming Lu, RA Student, Marine Genomics Unit (Satoh Unit)

Title: " The phylogenetic position of dicyemid mesozoans and the genomic changes of adaptation to the parasitic lifestyle"

Abstract: Understanding evolutionary history of animals has been a research subject for more than one century, and obtaining the data from enigmatic taxa is essential to better comprehend animal evolution. Dicyemids have been proposed as members of the Spiralia; however, their phylogenetic position remains controversial, leading to hypothetical scenarios of spiralian evolution remain contentious. Dicyemids are microscopic endoparasites inhabiting the renal sacs of some cephalopods, and have long fascinated biologists because of their highly simplified body organization and poorly known life-cycles. Their simple body plan, consisting of approximately 40 cells without differentiated organs, may be the adaptation to a parasitic lifestyle. Previously available data have not clarified their phylogenic affinity, and the genomic background of morphological and physiological changes for adapting the parasitic lifestyle are not well studied. Taking advantage of next-generation sequencing technology, we can utilize large molecular data to enable investigation of the phylogeny of animal taxa that lack uniting synapomorphies, and to explore genomic changes of adaptation to the parasitic lifestyle.

In the present study, we first decoded the transcriptome of Dicyema japonicum, and perform phylogenomic analyses to resolve the phylogenetic position of dicyemids within the Spiralia. Our results indicated that dicyemids are a group of morphologically reduced spiralian, having a close affinity to the Orthonectida, and they diverged early as a sister group to the Rouphozoa. Second, we developed a workflow to eliminate the host octopus contamination, and obtained a good-quality dicyemid genome assembly. The genome size of D. japonicum is reduced to 68 Mbp with extraordinarily shortened introns, which is similar to their highly simplified body organization corresponding to their parasitic life style. Besides, only two Hox genes that control the body plan along the anterior-posterior axis were found in our predicted gene models.
 

Refreshments will be served afterwards. We hope to see you there!
 

Sincerely,
 

Internal Seminar Organizing Committee:

Marylka Yoe Uusisaari
Bianca Sieveritz
Rob Campbell
Margaret Mars-Brisbin
Lauren Dembeck
Maeva Techer
Jigyasa Arora
Yuka Suzuki