Ectopic expression of Tollo/Toll‐8 antagonizes Dpp signaling and induces cell sorting in the Drosophila wing

Abstract

The wing imaginal disc of Drosophila consists of the primordia for the adult wing and the body wall. The zinc-finger transcription factor Teashirt (Tsh) is expressed in the region proximal to the wing primordium and regulates the formation of the wing-body wall boundary. Here, we report that Tollo/Toll-8, a member of Toll family transmembrane proteins, is also expressed proximal to the wing domain. Ectopic expression of Decapentaplegic (Dpp), a morphogen for wing development, represses tollo expression in the proximal domain. Likewise, misexpression of Tollo in the presumptive wing strongly antagonizes the effects of Dpp signaling. The extracellular domain of Tollo containing the Leucine-Rich Repeats (LRR) is required for the inhibition of Dpp signaling in the wing. Furthermore, clones of cells with Tollo overexpression are sorted out from the surrounding wild-type cells, resulting in the formation of epithelial folds around the clone boundaries. Tsh is ectopically induced at the border of Tollo-expressing clones. Despite the strong effects of Tollo overexpression on Dpp signaling and cell sorting, loss-of-function tollo mutants are viable with normal external morphology. Our data suggest that Tollo function might be redundant but is sufficient to antagonize Dpp signaling and induce sorting of Tollo expressing cells from the wing cells to develop proximal cell fate.

Toll-8/Tollo Negatively Regulates Antimicrobial Response in the Drosophila Respiratory Epithelium

“…spz rm7 i s a null allele which prevents Toll pathway activation [5]. yw, Drs-GFP [ 27 ], Dpt-Cherry [58], Tollo C5 (this work), Tollo R5A [32], Tollo 145 [59], UAS-Tollo IR (VDRC #9431), UAS-Tollo::Myc [31], DNT1 41 [46], UAS-spz2 IR (VDRC #26115), Ect4 EY04273 BL#15733, Df(3L)ED4408 BL#8065, Tl 3 BL#3238 (a dominant gain-of-function allele of Tl, Btl-Gal4 BL#8807, UAS-myrRFP BL#7118, act>CD2>Gal4 BL#4780, cad-EGFP BL#30875, Vkg-GFP (a gift from Michel Sémériva), hs-Gal4 BL#2077, Relish E20 [60], imd 1 [5], UAS-spz act [30], dMyd88 c03881 [34], UAS-PGRP-LC::GFP (a gift from François Leulier) and Dif 1 [61]. Generation of the Tollo C5 allele was performed as described in [62] using the two following inserted elements: d01565 and PBacf05248 [63].…”

NF-κB/Rel-Mediated Regulation of the Neural Fate in Drosophila

“…Toll-8-Gal4 drives GFP reporter gene expression at very high levels in the lateral halves of the notum in discs at the third larval instar (Figure 3A,B). In situ hybridization with a Toll-8 probe revealed a very similar pattern of expression (Figure 3C), see also [27]. This covers the region where most of the bristles form, except the dorsocentral and scutellar bristles that arise just at the border where expression levels fall.…”

The BTB/POZ-ZF Transcription Factor dPLZF Is Involved in Ras/ERK Signaling During Drosophila Wing Development

“…Therefore, Ras/ERK activation in a specific row of cells determines the fate of the cells as future wing veins. Consistent with this observation, loss-of-function mutations of the Ras/ERK pathway components result in loss of veins, whereas gain-offunction alleles and/or overexpression of these components induce ectopic vein development (Brunner et al, 1994;Kim et al, 2006;Prober and Edgar, 2000;Sturtevant and Bier, 1995). Additionally, phosphorylated cytoplasmic ERK promotes vein differentiation in the developing wing vein and margin cells during the larval and early pupal stage (Marenda et al, 2006).…”