The researchers identified the genes and proteins responsible for the rapid retraction of heliozoan arms in response to changes in the environment. This is one of the fastest known examples of cell motility. Raphidocystis contractile It is a species of eukaryote found in fresh, brackish and sea water from the Heliozoa group. These organisms are known as “sunworms” because of their spreading finger-like arms, or axopodia, which give them a sun-like appearance.

axopodia R. contractile It consists of alpha-beta-tubulin heterodimers that form microtubules. Despite its ability to quickly retract its arms in response to stimuli, the mechanism behind its rapid shortening remains a mystery.

To this end, a research team including Professor Motonori Ando of Okayama University, Japan, Dr Riza Ikeda (both from the Cell Physiology Laboratory) and Associate Professor Mayuko Hamada (from the Ushimado Marine Institute) investigated the mechanism involved. in one of the fastest cell movements in life.

So where did it all start? Sharing the motivation behind his research, Prof. “Recently, a wide variety of heliozoites have been found in various hydrospheres of Okayama Prefecture, suggesting that a wide variety of sunworm species lived in the same environment. We are trying to unravel the mysteries surrounding these simplest things and gradually broaden the horizons of our knowledge.”

The authors began their work by immunolabeling the tubulin protein and observing its movement before and after axopodia contraction. They found that prior to shortening, tubulins were systematically located along the entire length of the axopodia, but rapidly accumulated on the cell surface after removal of the axopodia. This led them to hypothesize that during the rapid retraction of axopodia the microtubules were instantly disintegrated into tubulin. However, microtubule degradation is not usually a rapid phenomenon; It’s going pretty slow.

So how? R. contractile Could he achieve this change so quickly?

The researchers hypothesized that this was possible if the microtubules were dividing into multiple sites at once. To confirm their hypothesis, the authors decided to find the proteins and genes involved in the abrupt division of microtubules. R. contractile. Their findings were recently published Journal of Eukaryotic Microbiology.

The researchers performed de novo transcriptome sequencing (analysis of genes expressed in a cell at a given time) and identified about 32,000 genes. R. contractile. This gene sequence was most similar to that found in protozoa (unicellular organisms) followed by multicellular organisms (multicellular organisms with well-differentiated cells; this includes humans and other animals).

Homology and phylogenetic analysis of the resulting gene set revealed several genes (and their corresponding proteins) involved in the destruction of microtubules. The most important among these were the catanin p60, kinesin and calcium signaling proteins. Katanin p60 was involved in the control of axopodial arm length. Several copies of the kinesin gene have been found. Among the kinesins identified, kinesin-13, an important microtubule destabilizing protein, was found to play an important role in rapid axopodia shortening. Calcium signaling genes regulate the flow of calcium ions from its environment to the cell and induction of axopodial retraction.

The researchers also noticed the absence of genes associated with flagellum formation and motility, suggesting that axopodia R. contractile It did not evolve from flagella. Although many genes remain unclassified, the newly created gene set will serve as a benchmark for future studies aimed at understanding axopodial motility. R. contractile.

Heliozoan axopodia can act as a sensitive sensor. They can detect even the smallest changes in the environment, such as heavy metal ions and anticancer drugs. Discussing his vision for the future, Professor Ando said, “We believe that the axopodial response of heliozoans can be used as an index for the development of ad hoc devices to detect and monitor environmental and tap water pollution. It can also be used as a new bioassay system for the initial screening of new anticancer drugs. In the future. “We plan to continue working together as a team to advance basic and applied research on these organisms.”

Heliozoa proved once again that a single cell has the enormous potential to change the world. We wish the authors success in making their vision a reality!