Int. J. Dev. Biol. 46: 633 - 638 (2002)

Vol 46, Issue 4

Special Issue: Developmental Biology in Australia and New Zealand

Homeotic genes influence the axonal pathway of a Drosophila embryonic sensory neuron

Published: 1 July 2002

David J Merritt and Paul M Whitington

School of Life Sciences, The University of Queensland, Brisbane, Australia. dmerritt@zen.uq.edu.au

Abstract

Each abdominal hemisegment of the Drosophila embryo has two sensory neurons intimately associated with a tracheal branch. During embryogenesis, the axons of these sensory neurons, termed the v'td2 neurons, enter the CNS and grow toward the brain with a distinctive pathway change in the third thoracic neuromere. We show that the axons use guidance cues that are under control of the bithorax gene complex (BX-C). Pathway defects in mutants suggest that a drop in Ultrabithorax expression permits the pathway change in the T3 neuromere, while combined Ultrabithorax and abdominal-A expression represses it in the abdominal neuromeres. We propose that the axons do not respond to a particular segmental identity in forming the pathway change; rather they respond to pathfinding cues that come about as a result of a drop in BX-C expression along the antero-posterior axis of the CNS.