New cellular ‘organelle’ discovered inside fruit-fly intestines

Amazing stuff! Can you believe it! The tiny fruit fly is one of the most intensely studied objects for decades and they still discover new fundamental things? Hundreds, if not thousands of scientists have researched this insect almost ad nauseam!

"Now, researchers have discovered a tiny structure inside animal cells that acts like a reservoir of phosphate, helping to regulate levels of the nutrient inside cells and triggering processes that maintain tissues when it is in short supply. The researchers classify the structure as a new type of organelle — fundamental structures in cells, such as the nucleus, mitochondria and the membrane, that function as miniature organs in its body.
“This is one of the first studies to actually find phosphate storage in an animal cell,”  ..."

From the abstract:

"Inorganic phosphate (Pi) is one of the essential molecules for life. However, little is known about intracellular Pi metabolism and signalling in animal tissues. Following the observation that chronic Pi starvation causes hyperproliferation in the digestive epithelium of Drosophila melanogaster, we determined that Pi starvation triggers the downregulation of the Pi transporter PXo. In line with Pi starvation, PXo deficiency caused midgut hyperproliferation. Interestingly, immunostaining and ultrastructural analyses showed that PXo specifically marks non-canonical multilamellar organelles (PXo bodies). Further, by Pi imaging with a Förster resonance energy transfer (FRET)-based Pi sensor, we found that PXo restricts cytosolic Pi levels. PXo bodies require PXo for biogenesis and undergo degradation following Pi starvation. Proteomic and lipidomic characterization of PXo bodies unveiled their distinct feature as an intracellular Pi reserve. Therefore, Pi starvation triggers PXo downregulation and PXo body degradation as a compensatory mechanism to increase cytosolic Pi. Finally, we identified connector of kinase to AP-1 (Cka), a component of the STRIPAK complex and JNK signalling, as the mediator of PXo knockdown- or Pi starvation-induced hyperproliferation. Altogether, our study uncovers PXo bodies as a critical regulator of cytosolic Pi levels and identifies a Pi-dependent PXo–Cka–JNK signalling cascade controlling tissue homeostasis."

New cellular ‘organelle’ discovered inside fruit-fly intestines Fruit-fly cells use previously unknown complex cellular structures to store phosphate, a molecule essential to life

A phosphate-sensing organelle regulates phosphate and tissue homeostasis (no public access)

Three of the newly discovered organelles in a fruit-fly intestinal cell. The organelles seem to be a reservoir of phosphate, a molecule essential to life.