When studying phosphate transport in the intestines of fruit flies, researchers at Harvard Medical School’s Blavatnik Institute and the Department of Genetics came across a remarkable new organelle. Their findings are discussed in a News and Views article published in the same journal as their results in Nature.
The majority of introductory biology courses begin with an introduction to organelles, which are the structures that carry out specific functions within the cell. The nucleus, where DNA is stored and translated into RNA, is one of the major organelles. the endoplasmic reticulum, where proteins are made from RNA; furthermore, the Golgi contraption, where enzymatic handling of proteins happens; and the mitochondrion, which powers the cell and is responsible for monitoring, regulating, and communicating with other cells.
A couple dozen other minor organelles exist inside creature cells, and it could have been expected that each organelle had been found after such countless long periods of exploration. Yet, not in this way, as itemized in the scientists’ new paper, “A phosphate-detecting organelle directs phosphate and tissue homeostasis.”
An experiment that showed that the digestive epithelium of the Drosophila (fruit fly) midgut is hyperproliferated and differentiates into enterocytes was the focus of the research team’s attention. Since inorganic phosphate is necessary for cell life, the team hypothesizes that this could be a survival strategy to increase the number of enterocytes that can absorb phosphate.
They also noticed that the expression of the gene PXo (CG10483) was lower in the state of phosphate depletion. The researchers devised a few interrogation experiments because they were interested in the PXo protein’s function. They observed the same effect as when inducing inorganic phosphate starvation was induced by either inhibiting PXo expression or completely deleting the gene. This suggests that PXo is essential for phosphate transport. We would have a fantastic addition to our understanding of phosphate metabolism and cellular signaling if the study had ended here, but there was more.
The researchers dubbed the newly discovered organelle that they discovered, PXo bodies, and immunoostaining and ultrastructural analyses revealed that PXo specifically appeared in a multilamellar membrane that was previously unknown. Phosphorus was essentially stored in the PXo bodies by the PXo. The PXo bodies degraded when PXo was downregulated or absent, releasing the phosphate backup storage into the cell.
More research is required, just like any good research concludes. The full functions and interactions of this new organelle must be mapped in subsequent research, which may also look for PXo bodies in other life forms.
More information: Chiwei Xu et al, A phosphate-sensing organelle regulates phosphate and tissue homeostasis, Nature (2023). DOI: 10.1038/s41586-023-06039-y
Emily Strachan et al, Phosphate-storing organelle discovered in fruit flies, Nature (2023). DOI: 10.1038/d41586-023-01410-5
