The researchers at Harvard Medical School's Blavatnik Institute have uncovered a previously unknown organelle, PXo bodies, which plays a crucial role in phosphate transport and storage. This significant finding challenges the assumption that all organelles had been identified, calling for further research to unravel the mysteries of PXo bodies and their broader implications in various life forms.
WHAT IS AN ORGANELLE?
Organelles are the specialised structures analogous to "organs" of the body as they perform specific cellular functions, contributing to the overall organization and functionality of the cell. Familiar organelles include the nucleus (housing DNA and facilitating its translation into RNA), the endoplasmic reticulum (translating RNA into proteins), the Golgi apparatus (processing proteins), and mitochondria (providing cellular energy and regulating cell functions). While minor organelles are recognized in animal cells, the recent research uncovers a new player in cellular biology.
WHO DISCOVERED IT?
A team of researchers at Harvard Medical School's Blavatnik Institute, specifically the Department of Genetics, have made a groundbreaking discovery while studying phosphate transport in the intestines of fruit flies. Their findings, published in the prestigious journal Nature, unveil a newly discovered organelle PXo body, challenging the notion that all organelles have been identified after years of scientific exploration.
WHAT ARE PXo BODIES?
Simply put, the organelle discovered, PXo bodies are storage sites for storage of phosphate ions.
Such bodies already have been seen and studied in bacteria, yeasts and plants but this is the first instance where these storage sites were discovered in an animal cell that too in an organism (Drosophila melanogaster aka the fruit fly) which has been studied in immense depth for more than a century.
HOW WAS THIS DISCOVERY MADE?
In their study titled "A phosphate-sensing organelle regulates phosphate and tissue homeostasis," the research team aimed to investigate how inorganic phosphate starvation affects the fruit fly midgut's digestive epithelium. They discovered that phosphate depletion triggered hyperproliferation (proliferation of cells by rapid division) and differentiation (cells acquiring specialised features) of enterocytes (intestinal cells involved in phosphate absorption) possibly as a survival mechanism to enhance phosphate absorption.
During their investigation, the researchers noted a correlation between phosphate depletion and decreased expression of the PXo gene (CG10483). Intrigued by the role of the PXo protein, they conducted further experiments, inhibiting PXo expression and deleting the gene entirely. Remarkably, the observed effects mirrored those induced by inorganic phosphate starvation, indicating that PXo plays a vital role in phosphate transport.
However, the researchers' breakthrough did not end there. Through immunostaining and ultrastructural analyses using electron microscope, they identified a previously unknown multilamellar membrane associated with the PXo protein. In recognition of this new organelle, the scientists named it PXo bodies. The PXo bodies were found to store phosphate, and when PXo expression was reduced or absent, the organelles degraded, releasing the stored phosphate into the cell.
WHY IS THIS DISCOVERY IMPORTANT?
This groundbreaking organelle discovery in the model organism, Drosophila melanogaster (fruit fly) comes to show how little we know about an already well studies organism. This paves the way for future investigations. Scientists will need to explore the full scope of functions and interactions of this novel organelle and potentially search for PXo bodies in other organisms. Such endeavors promise to deepen our understanding of phosphate metabolism, cellular signaling, and the intricate mechanisms governing cellular homeostasis.
The report, published May 3 in the journal Nature(opens in new tab), notes that the organelle, found in the fruit fly gut, sequesters phosphate from food and regulates its availability in the cell.
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