ABSTRACT
The Drosophila embryonic tracheal network is an excellent model to study tube size. The chitin-based apical luminal matrix and cell polarity are well known to regulate tube size in Drosophila trachea. Defects in luminal matrix and cell polarity lead to tube overexpansion. Here, we address the novel function of the rebuff (reb) gene, which encodes an evolutionarily conserved Smad-like protein. In reb mutants, tracheal tubes are moderately over-elongated. Despite the establishment of normal cell polarity, we observed significantly reduced apical luminal matrix in reb mutants. Among various luminal components, luminal Obstructor-A (ObstA) is drastically reduced. Interestingly, ObstA is localized in vesicle-like structures that are apically concentrated in reb mutants. To investigate the possibility that reb is involved in the endocytosis of ObstA, we analyzed the co-localization of ObstA and endocytic markers in reb mutants. We observed that ObstA is localized in late endosomes and recycling endosomes. This suggests that in reb mutant trachea, endocytosed ObstA is degraded or recycled back to the apical region. However, ObstA vesicles are retained in the apical region and are failed to be secreted to the lumen. Taken together, these results suggest one function of reb is regulating the endocytosis of luminal matrix components.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: L.J.; Methodology: R.R.C., L.J.; Formal analysis: R.R.C., L.J.; Investigation: R.R.C., A.S., Y.Y., L.J.; Writing - original draft: L.J.; Writing - review & editing: A.S., L.J.; Supervision: L.J.; Project administration: L.J.; Funding acquisition: L.J.
Funding
This project was supported by the Oakland University Research Excellence Fund 10126 and National Institute of Health R15GM100369 grant to L.J.
- Received June 25, 2018.
- Accepted July 19, 2018.
- © 2018. Published by The Company of Biologists Ltd
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