Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors.
Different classes of photoreceptors (PRs) allow animals to perceive various types of visual information. In the Drosophila eye, the outer PRs of each ommatidium are involved in motion detection while the inner PRs mediate color vision. In addition, flies use a specialized class of inner PRs in the "dorsal rim area" of the eye (DRA) to detect the e-vector of polarized light, allowing them to exploit skylight polarization for orientation. We show that homothorax is both necessary and sufficient for inner PRs to adopt the polarization-sensitive DRA fate instead of the color-sensitive default state. Homothorax increases rhabdomere size and uncouples R7-R8 communication to allow both cells to express the same opsin rather than different ones as required for color vision. Homothorax expression is induced by the iroquois complex and the wingless (wg) pathway. However, crucial wg pathway components are not required, suggesting that additional signals are involved.
Wernet
Mathias F
MF
New York University, Department of Biology, 100 Washington Square East, New York, NY 10003, USA.
Labhart
Thomas
T
Baumann
Franziska
F
Mazzoni
Esteban O
EO
Pichaud
Franck
F
Desplan
Claude
C
D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning; D003116:Color; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D005123:Eye / Q000166:cytology / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism* / Q000528:radiation effects*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D015398:Signal Transduction; D051155:Wnt1 Protein
D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D011518:Proto-Oncogene Proteins; D051155:Wnt1 Protein; C108704:hth protein, Drosophila; C074622:wg protein, Drosophila