The biomolecule diphthamide is essential for the correct formation of proteins in cells. When humans are infected with diphtheria, the diphtheria toxin alters diphthamide, so life-threatening complications can occur due to altered protein formation. Until now, diphthamide was only known from animals and fungi. A research team has just shown that the biomolecule is also present in plants.
Researchers have also shown that their formation can be affected by certain environmental factors. This was published in the magazine nature of communication, July 11, 2022.
The study was carried out in the department of Ute Krämer, with input from the research group of Prof. Raffael Schaffrath of the University of Kassel and Prof. Lorenz Adrian of the Technical University of Berlin, as well as other research groups in Germany.
Plants without diphthamide grow less
The biomolecule diphthamide is a natural modification of the protein called elongation factor 2 of many organisms. This protein is one of the components responsible for building all the proteins in the cell. “This modification has long been known to be the target of diphtheria toxin, which can cause life-threatening complications in people infected with diphtheria by preventing cellular protein synthesis,” explains Ute Krämer. “Diphtheria bacterial infections have been documented since ancient times and were widely feared until the 19th century, before a vaccine was developed. »
Until now, diphthamide had only been identified and studied in detail in animal organisms and baker’s yeast, as a model organism for medical research. Ute Krämer’s team has now shown that diphthamide is also formed in plants and serves an important function: If the plant does not have the ability to form diphthamide, there is a higher error rate in protein biosynthesis. Also, plant growth is reduced due to decreased cell division. Several additional alterations in central cellular regulatory processes could contribute to causing growth restriction.
Stress influences diphthamide formation
According to the study results, the essential initial step of diphthamide biosynthesis known to mammals and yeasts also occurs in plants. So it is likely that this is also the case for the later steps leading to diphthamide now being detected in plants. “However, what is completely new is that not only genetic defects can lead to loss of diphthamide,” explains Ute Krämer. “Environmental stress, particularly an excess of the trace nutrient copper or the environmental toxin cadmium, also inhibits diphthamide formation in plants. In the presence of high concentrations of copper, human cells also showed diphthamide deficiency. These results identify a new factor that influences plant growth rates and could also contribute to a better understanding of how diseases develop. “Whether plant pathogens also use diphthamide as an Achilles’ heel, just as the diphtheria pathogen does in humans, must now be investigated,” says Ute Krämer.