This parasite transforms plants into zombies


A mustard plant infected with a particular parasite grows strangely and its growth is distorted by small invaders. Its leaves take on odd shapes, its stems forming a shrub structure called a witch’s whip and it can grow flowers that do not produce seeds. After all, it lives longer in adolescence than its unaffected brethren.

“It looks like a child,” said Saskia Hoganhout, a scientist at the John Innes Center in the UK, who studies the life cycle of a parasite, known as aster yellow phytoplasma.

Neighbors of the plant age, reproduce and die, but the young host of phytoplasma continues. It is like a mixture between an immature vampire and a zombie host, whose body helps with its parasitic needs, i.e., stimulates the sap-sucking insects to feast on the body fluids of the plant as much as possible. When insects ingest parasites, they spread to new hosts, and the entire “night-dracula” cycle of living organisms reappears.

How the parasite exerts such a wide range of control is of greater interest than scientists — phytoplasmas can cause destructive disease in crop plants such as carrots. In an article published in the magazine September GoHoganhout and her colleagues reveal that these creeping changes are triggered by the work of a protein from the parasite SAP05, which stands in the way of plant maturation.

SAP05 is not the first substance created by this phytoplasma, and scientists have linked it to the symptoms it causes. The team listed the parasite’s gene a few days ago and pointed out a few proteins that could be used to zombie victims. But in the new paper, they explain how SAP05 triggers some surprising effects, such as a lifetime extension.

SAP05 binds to two groups of plant proteins that regulate the expression of genes used in growth. Once it sticks to them, it causes them to break through the plant’s own garbage disposal machine. As a result, the plants appear frozen, unable to progress.

It makes sense from a parasite perspective. When the host plants mature normally, they will grow flowers and produce seeds, devoting all their energy to creating the next generation of plants. Before long they will shed their leaves and wither.

“You can imagine this situation is not the right situation for the parasite,” Hoganhout said.

Parasites benefit from the fact that the plant is infertile, so they can centralize its ability to produce offspring of microorganisms. They benefit from the fact that the plant is alive and full of delicious fruit juices as much as possible, it is good to make it easier for insects to feed on it.

Unsurprisingly, however, scientists have found that SAP05 attaches to a specific part of the cell removal machine to achieve this goal. By modifying the composition of that piece, they can drastically reduce the effects of SAP05. Plants – in this case Arabidopsis taliana, A small laboratory-type small mustard plant – with this change did not grow into the broom form of witches, and they did not live much longer than unaffected plants.

But that doesn’t mean they are better. Plants designed to avoid SAP05 had a particularly short lifespan when exposed to the parasite. SAP05 appears to provide some protection against the stress of infection, thus making it easier for the host to tolerate. Without it, the plant may be free to continue its maturation, but it is more susceptible to disease than zombie plants, which are more vulnerable to other effects of the parasite. Zombies live and are protected by the creature that rides within them.

This control is elegant with the life cycle of juice-eating insects, Hoganhout said. Insects, after eating a plant, become infected with the parasite and lay eggs on it. At the same time as the parasite takes over, the eggs mature.

When young insects hatch, probably after 10 days, the extended lifespan of the plants is sufficient. The rider will have their good friend Phytoplasma.

“The parasite is now on the rise, just in time,” Hoganhout said.

This article first appeared The New York Times.

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