How Does the Venus Flytrap Close Its Leaves?
Although Venus flytrap plants do not have brains and nervous systems like other animals, they close their traps when touched. So how can plants do this? How Does the Venus Flytrap Close Its Leaves?
Scientists at the Scripps Research Institute have uncovered the three-dimensional structure of a protein channel that can cause the Venus flytrap plant to close in response to its prey. The structure of this channel, called Venus flytrap1, demonstrated in a study published four days ago in Nature Communications, sheds light on longstanding questions about the high sensitivity of Venus flytrap plants to touch. The structure, which provides a better understanding of similar proteins in living things, including plants and bacteria, also sheds light on how proteins with similar functions (mechanosensitive ion channels) in the human body work.
“Although Venus flytrap plants are very different from humans, by studying the structure and function of these mechanosensitive channels we can gain a broader understanding of how cells and living things respond to touch and pressure,” says Andrew Ward, co-senior author of the study and a professor at the Scripps Research Institute.
“With each new mechanosensitive channel we examine, we gain a better understanding of how these proteins sense the applied force and turn it into action,” says co-senior author Ardem Patapoutian of the Scripps Research Institute. “These, in turn, reveal more about human biology and health.” Patapoutian’s work on the mechanosensitive channels that allow the body to perceive touch and temperature earned him the Nobel Prize in Medicine.
Mechanosensitive ion channels look like tunnels through cell membranes. The channels that open when stimulated by movement cause an influx of ion-charged molecules. Cells also change their behavior in response; For example, a neuron cell can send a signal to its neighbor. The ability of cells to perceive pressure and movement is also important in many internal processes that take place in the body, from people’s sense of touch and hearing, to the feeling that the bladder is full, to the ability of the lungs to perceive the amount of air taken.
Scientists previously focused on three ion channels in the Venus flytrap plant. These channels were thought to be related to the carnivorous plant’s ability to close its leaves when the sensitive trigger hairs are touched. A channel named Flykapan1 caught the attention of researchers because of its genetic sequence similar to a family of mechanosensitive channels (MscS) found in bacteria.
Co-first author Sebastian Jojoa Cruz, a graduate student at the Scripps Research Institute, explains: “The variants of this channel found throughout evolution suggest that the channel must maintain some essential and important functions in different species.”
Using the cold electron microscopy method in the new study, the researchers analyzed the precise sequence of molecules found in the Venus flytrap 1 protein channel. Cold electron microscopy is one of the cutting-edge methods of revealing the positions of atoms in a frozen protein sample. The scientists discovered that Flycatcher1 is in many ways similar to bacterial MscS proteins (groups of seven identical helices surrounding a central channel). But, unlike other MscS channels, Flykapan1 has an unusual linker region that extends outward from each helix group. Each of the connectors can move up and down, just like a switch. When the research team determined the structure of Sinekkapan1, they discovered that there were six connectors in the lower position and only one in the upper position.
“The architecture of the channel core in Flycatcher1 was similar to other channels that have been studied for years, but these binding sites were surprising,” says Kei Saotome, co-first author of the new study and formerly a postdoctoral fellow at the Scripps Research Institute.
To clarify the function of the switches, scientists changed the connector, distorting the upward-facing position of the switch. As a result, they discovered that Sinekkapan1 no longer responds to pressure in the usual way; The channel, which normally closes with the release of pressure, has remained open for a longer period of time.
“The far-reaching effect of the mutation suggests that these seven linkers are relevant to the way the channel works,” said co-senior author Swetha Murthy, formerly a postdoctoral fellow at Oregon Health and Science University’s Vollum Institute and formerly a postdoctoral fellow at the Scripps Research Institute.
Now that the molecular structure has been resolved, the research team plans to conduct future studies on the function of Flycatcher1 and thus understand how different applied sequences affect the function of the channel. Whether Venus flytrap1 is solely responsible for closing the leaves of the Venus flytrap; otherwise, further work is needed to determine whether other suspected channels also have complementary roles.