Characterization of the hermaphroditic reproductive system and sexual development in the planarian Schmidtea mediterranea

Chong, Tracy Pei Mei

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https://hdl.handle.net/2142/44470 Copy

Description

Title

Characterization of the hermaphroditic reproductive system and sexual development in the planarian Schmidtea mediterranea

Author(s)

Chong, Tracy Pei Mei

Issue Date

2013-05-24T22:17:19Z

Director of Research (if dissertation) or Advisor (if thesis)

Newmark, Phillip A.

Doctoral Committee Chair(s)

Henry, Jonathan J.

Committee Member(s)

• Newmark, Phillip A.
• Belmont, Andrew S.
• Brieher, William M.
• Raetzman, Lori T.

Department of Study

Cell & Developmental Biology

Discipline

Cell and Developmental Biology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• dm domain
• planarian
• schmidtea mediterranea
• sex determination
• sexual development
• germ cells
• hermaphroditic reproductive system

Abstract

When it comes to sexual reproduction, there are many means to an end. Although there are numerous types of mating systems and sex determination mechanisms, as well as different modes of germ cell development, there is one clear goal – to produce new offspring with unique genetic makeup. Scientists have long been intrigued by this diversity, and biologists today are delving deep into the molecular mechanisms underlying the variety of methods utilized by organisms to reproduce sexually. There are two strains of the freshwater planarian, Schmidtea mediterranea: the sexual strain is a cross-fertilizing hermaphrodite with reproductive organs that develop post-embryonically; the asexual strain reproduces by transverse fission and does not develop reproductive organs. This interesting biology, combined with recently developed molecular, cellular, and genomic tools make the planarian an attractive model organism in which to study germ cell development. Also, the planarian is a member of the Lophotrochozoan clade, a critical group for understanding the evolutionary transitions between mating systems and the mechanisms underlying diverse modes of sex determination. To characterize the difference between asexual and sexual planarians, we performed microarray analyses to identify genes that were expressed differentially in sexual and asexual planarians. We also used immuno- and lectin-staining to visualize components of the reproductive system. These complementary approaches allowed us to study the genetic and morphological differences between the two distinct modes of reproduction in planarians. We next showed that Smed-dmd-1, a conserved DM domain transcription factor, provides a sex-specific niche required for the specification of male germ cells and maintenance of “maleness” in the planarian. Finally, we found that the male-specific expression of dmd-1 is retained in a derived, dioecious flatworm, Schistosoma mansoni. The male-specific expression of dmd-1 in both the hermaphroditic S. mediterranea and dioecious S. mansoni suggest one means by which modulation of sex-specific pathways can drive the transition from hermaphroditism to dioecy.

Graduation Semester

2013-05

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http://hdl.handle.net/2142/44470

Copyright and License Information

Copyright 2013 Tracy Chong

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