A Determinant for Directionality of Organelle Transport in Drosophila Embryos

Steven P. Gross, Yi Guo, Joel E. Martinez, Michael A. Welte

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


Background: Motor-driven transport along microtubules is a primary cellular mechanism for moving and positioning organelles. Many cargoes move bidirectionally by using both minus and plus end-directed motors. How such cargoes undergo controlled net transport is unresolved. Results: Using a combination of genetics, molecular biology, and biophysics, we have identified Halo, a novel regulator of lipid droplet transport in early Drosophila embryos. In embryos lacking Halo, net transport of lipid droplets, but not that of other cargoes, is specifically altered; net transport is minus-end directed at develop-mental stages when it is normally plus-end directed. This reversal is due to an altered balance of motion at the level of individual organelles; without Halo, travel distances and stall forces are reduced for plus-end and increased for minus-end motion. During development, halo mRNA is highly upregulated just as net plus-end transport is initiated (phase II), and its levels drop precipitously shortly before transport becomes minus-end directed (phase III). Exogenously provided Halo prevents the switch to net minus-end transport in phase III in wild-type embryos and induces net plus-end transport during phase II in halo mutant embryos. This mechanism of regulation is likely to be of general importance because the Drosophila genome encodes a family of related proteins with similar sequences, each transiently expressed in distinct domains. Conclusions: We conclude that Halo acts as a directionality determinant for embryonic droplet transport and is the first member of a new class of transport regulators.

Original languageEnglish (US)
Pages (from-to)1660-1668
Number of pages9
JournalCurrent Biology
Issue number19
StatePublished - Sep 30 2003

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences


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