All life on Earth, from the tiny microbes near hydrothermal vents under our oceans to the giant blue whales swimming above, are simply codes written in DNA. As Richard Dawkins would say, life is a product of selfish genes. DNA is copying itself into the future while the organisms transmitting the DNA dies. A favorite saying of mine is: the chicken is the egg’s way of making another egg.
Biologists get to use the tools of science to investigate the details and explain the wondrous stories of how each species, directed by its nucleic acid code, accomplishes the continuation of the code’s existence.
The life cycle of parasites ranks near the top of the most exciting and perplexing stories list. I have written about some of these life cycles in the past. There are stories about fungi taking over insect brains, wasps whose sting creates zombie prey, worms that cause frogs to grow extra limbs so birds can easily catch them, and even parasites that cause rats to seek out cats. The list goes on, and if the stories of parasites interests you, please pick up the book “Parasite Rex” by Carl Zimmer. The method that the code of life uses to continue can get pretty dark from a human perspective.
A recent article published in the journal Cell is titled “Parasitic modulation of host development by ubiquitin-independent protein degradation.” This article takes a deep dive into the details that underlie the ability of a parasite to manipulate the host. Parasitic life cycles can get complex and involve multiple organisms, and science is slowly unraveling the often complicated parasitic life cycle. The story that this article unravels is of a parasitic bacterium that is transmitted via insects into plants.
Phytoplasma bacteria have been known as parasitic manipulators of plants for some time now, but how they accomplish the task has been unknown. These tiny microbes can cause plants to grow extra shoots and branches filled with leaves called a “witches broom.” The shoots are sterile and produce no flowers. The bacteria even extend the lifespan of the plant and reproduce in the vascular phloem of a plant. The phloem transports the sugars, made in the leaves by photosynthesis, around the plant. A variety of insects often tap into the phloem like mosquitos sucking blood. In short, these microbes create a plant that lives a long time and grows tons of new branches giving the bacteria more places to live and reproduce and more places for insects to pick up the bacteria and carry them off to new plants.
The bacteria create their perfect zombie plant home by utilizing a protein called SAP05. This protein binds with critical regulators of development known as transcription factors and with a protein called RPN10. The RPN10 protein is a marker for protein destruction, so anything linked with RPN10 gets broken down. By controlling the destruction of the proteins that regulate the plant’s growth and development, SAP05 has hijacked the system. The full article is free to read if you Google it and contains much more detail. It also discusses how the researchers engineered the RPN10 of a plant to stop the bacteria’s take over.
Parasitic bacteria creating zombie plant homes to live in and spread their code via insect vectors, just one more story in the exciting life cycles of parasites.