How plants respond to gravity, pressure and impact

Scientists at Washington University at St. Louis was the first to identify two proteins that act as mechanically sensitive ion tube activity in plant roots. They have long known that plant cells respond to physical forces. Until now, however, proteins that control the reaction of ion tubes remain a mystery.

From the name we can see that mechanical sensitive tubes are the pathways through the cell membrane that respond to physical forces such as gravity, pressure or impact. Under certain effects the tube will be opened to allow the circulation of ions such as calcium or potassium circulating through the cell. Some other forces cause the tube to close, preventing the flow.

Cellular ion flow flow is electrophysiologically determined by a technique called Patch - Clamp. However, the nature of circulating pipes is still unclear. Currently, identifying related proteins makes it easier to understand which circulation tubes are responsible for the function.

Dr. Elizabeth Haswell, assistant professor of biology at Washington University (St. Louis) and project lead investigator, said: 'We are still exploring the properties of mechanical sensitive tubes in plants for 20 years. This is the first time that proteins are responsible for performing the above activities.

The researchers discovered two proteins that control mechanically sensitive ion tube activity in Arabidopsis roots.(Photo: iStockphoto)

Plants have, bacteria also

According to research published in the May 20 issue of Current Biology, two proteins that control the activity of ion tubes in Arabidopsis roots are MSL9 and MSL10. MSL stands for MscS-Like protein cluster (MscS-like protein) due to its equivalence to the bacterial tube system called MscS (mechanical sensitive tube with small conductivity). Although bacteria and plants are not very evolutionary, this study suggests that bacterial cells and plant cells may have used the same protein to control the mechanical forces.

To prove that the tubes are actually mechanically sensitive tubes, Haswell's French colleagues applied the Patch-Clamp method to determine the motion of ions across the membrane of Arabidopsis root when pressure in the cells increase. The experiment demonstrated that increased cell pressure also increased ion flow through the membrane. Similarly, when the internal pressure decreases, ion flow also decreases.

To know whether MSL9 and MSL10 are related to ion flow, Haswell created the mutant strain of Arabidopsis without the two proteins. When the plant root cells lack MSL9 and MSL10, ion flow flow through the membrane is almost unchanged when the pressure in the cell increases. In other words, without these two proteins, ion tubes are almost inactive. But different proteins are their causes.

Two types of combinations

After demonstrating that MSL 9 and MSL 10 are responsible for performing ion tube activity, Haswell and his colleagues set out to determine whether both proteins are involved in controlling the reaction or just a protein makes The main task. So they experimented with plants that lacked one of these two proteins and were surprised to discover that the only cell with MSL9 controls one type of action and the cell with only MSL10 controls another type of action. Importantly, cells with both proteins control the third type of action. This suggests that both MSL9 and MSL10 are necessary in the process of forming reactions of mechanically sensitive ion tubes in the roots of Arabidopsis rabies.

Haswell and colleagues suggested that ion tubes are made up of sub-molecular structures of MSL9 protein and MSL10. Their combined structure creates a mechanical-sensitive ion tube reaction that is specific to wild type plants, but not in any mutant plant line.

Although two proteins have been discovered that control the reaction of ion tubes in Arabidopsis roots, the mystery remains. In order to determine why the mutant line is defective and find out the purpose of the ion tube, Haswell's team planted plants without these tubes under certain special conditions, such as high salt rates, wall separates roots or dehydrates.

Haswell said: 'We have conducted hundreds of experiments, but we have never seen a difference between the mutant line and the natural stream. But this is certainly one of the next great steps to find out the true behavior of the tubes and why they are important. '