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First atomic map of potato pathogen reveals potential infection mechanism

Plants are susceptible to a wide range of pathogens. For the common potato plant, one such threat is Pectobacterium atrosepticum, a bacterium that causes stems to blacken, tissues to decay, and often leads to plant death, resulting in significant agricultural losses each year.

In 2012, researchers isolated a new virus that infects and kills this bacterium—a bacteriophage named φTE (phiTE). Now, for the first time, scientists have uncovered the atomic structure of φTE, revealing a possible mechanism of infection that may be more complex than previously thought.

The study, earlier this month in Nature Communications, is the result of a multidisciplinary collaboration between researchers from the Okinawa Institute of Science and Technology (OIST) and the University of Otago. It brings together expertise across several fields, including virology, structural biology, molecular genetics, protein engineering, biochemistry, and biophysics.

Belonging to one of the most pervasive viral classes, φTE is a bacteriophage that is of particular interest to the molecular genetics community. In addition to its role in combating plant pathogens, it serves as a model virus commonly used in research to study how bacteriophages interact with their host bacteria.

Using cryo-electron microscopy (cryo-EM), the team successfully captured the complete φTE virion at the atomic resolution. They discovered that the virus exhibits a unique topology when compared to other viruses in the same family.

These new insights helped understand the conformational changes that enable the virus to release its DNA into the host and initiate infection. φTE was also found to have a relatively larger capsid, likely to accommodate a bigger genome.

Additionally, the team identified structural elements that appear to play a critical role in maintaining the virion's stability and function. Direct visualization enabled them to resolve a protein known as the tape measure protein (TMP), which is important for the virion's assembly and function.

By comparing φTE to related viruses, they identified several shared features as well as notable differences. Based on these findings, the researchers proposed a model describing how φTE might initiate its attack on the host.

This research advances our understanding of bacteriophages, such as φTE, and could have significant implications. It will better equip scientists to design biological agents that can combat a range of bacterial plant diseases. These agents serve as valuable alternatives to traditional chemical treatments and antibiotics.