Tryptophan hydroxylase is required for eye melanogenesis in the planarian schmidtea mediterranea

Bramwell G. Lambrus, Olivier Cochet-Escartin, Jiarong Gao, Phillip A. Newmark, Eva Maria S Collins, James J. Collins

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Melanins are ubiquitous and biologically important pigments, yet the molecular mechanisms that regulate their synthesis and biochemical composition are not fully understood. Here we present a study that supports a role for serotonin in melanin synthesis in the planarian Schmidtea mediterranea.We characterize the tryptophan hydroxylase (tph) gene, which encodes the rate-limiting enzyme in serotonin synthesis, and demonstrate by RNA interference that tph is essential for melanin production in the pigment cups of the planarian photoreceptors. We exploit this phenotype to investigate the biological function of pigment cups using a quantitative light-avoidance behavioral assay. Planarians lacking eye pigment remain phototactic, indicating that eye pigmentation is not essential for light avoidance in S. mediterranea, though it improves the efficiency of the photophobic response. Finally, we show that the eye pigmentation defect observed in tph knockdown animals can be rescued by injection of either the product of TPH, 5-hydroxytryptophan (5-HTP), or serotonin. Together, these results highlight a role for serotonin in melanogenesis, perhaps as a regulatory signal or as a pigment substrate. To our knowledge, this is the first example of this relationship to be reported outside of mammalian systems.

Original languageEnglish (US)
Article numbere0127074
JournalPLoS One
Volume10
Issue number5
DOIs
StatePublished - May 1 2015

Fingerprint

Planarians
Tryptophan Hydroxylase
melanogenesis
Pigments
tryptophan
Serotonin
Melanins
serotonin
eyes
pigments
melanin
Pigmentation
Biological Pigments
pigmentation
synthesis
Light
5-Hydroxytryptophan
5-hydroxytryptophan
RNA Interference
RNA interference

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Lambrus, B. G., Cochet-Escartin, O., Gao, J., Newmark, P. A., Collins, E. M. S., & Collins, J. J. (2015). Tryptophan hydroxylase is required for eye melanogenesis in the planarian schmidtea mediterranea. PLoS One, 10(5), [e0127074]. https://doi.org/10.1371/journal.pone.0127074

Tryptophan hydroxylase is required for eye melanogenesis in the planarian schmidtea mediterranea. / Lambrus, Bramwell G.; Cochet-Escartin, Olivier; Gao, Jiarong; Newmark, Phillip A.; Collins, Eva Maria S; Collins, James J.

In: PLoS One, Vol. 10, No. 5, e0127074, 01.05.2015.

Research output: Contribution to journalArticle

Lambrus, Bramwell G. ; Cochet-Escartin, Olivier ; Gao, Jiarong ; Newmark, Phillip A. ; Collins, Eva Maria S ; Collins, James J. / Tryptophan hydroxylase is required for eye melanogenesis in the planarian schmidtea mediterranea. In: PLoS One. 2015 ; Vol. 10, No. 5.
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