New technologies are currently being explored to protect our agriculturally important plants from invading pathogens. The advent of mass monoculture, that is to say, enormous numbers of plants with a similar genetic background, has provided an almost perfect environment for a wide variety of invading organisms, including viruses, bacteria, fungi, and parasites.
Although plants are well defended by their innate natural immunity against invading organisms, they lack the fundamental adaptive immune system present in animals. There is an urgent need to develop new ways to allow plants to protect themselves. Recent advances raise the exciting possibility that at least some components of the adaptive immune systems of animals, through genetic engineering, can be added plant defenses against specific pathogens. Here we describe the a recent paper by Kourelis et al., researchers from the University of East Anglia in the United Kingdom that details this exciting development.
The researchers found the camelid nanobodies more convenient to work with firstly, because of their single chain. Secondly, nanobodies lack an Fc region, so they are unlikely to engage other cellular activities such as cytotoxicity.
They inserted the nanobody into a gene usually induced by plants to counter a pathogen as part of the innate immune system. This gene is activated when a plant is infected by one of a broad array of pathogens. When the plant was infected, this re-engineered antibody structure would be produced for the specific pathogen. They refer to the re-engineered antibody as a pikobody. Kourelis et al. used Potato virus X to demonstrate the binding and neutralization specificity of the pikobody, demonstrating the efficacy of this new plant antibody technology.
Six of the 11 fusions they developed did not exhibit autoimmune activities, meaning the engineered immune response did not turn on itself. From those six, four demonstrated hypersensitive cell death responses.
The researchers next tested their four candidates against live pathogens. Against a recombinant Potato virus X expressing fluorescent proteins, the top two performing pikobodies substantially reduced the accumulation of virus expressed compared to a control.
Further testing against Potato virus X revealed that stacking pikobodies allowed for enhanced reduction of virus accumulation.
While the pikobodies demonstrated a strong reaction to the Potato virus X sample, a different pikobody would need to be developed for every pathogen that could impact the plant, as the innate immune system is insufficient to ward off all pathogens.
Researchers emphasize that “nanobodies can be readily generated to bind virtually any antigen.” Plant pikobodies can be created against a broad range of plant pathogens, including but not limited to fungi, bacteria, protozoa, and viruses.
Pikobodies represent a vital step forward and a new pathway to create disease-specific plants capable of defending themselves against specific diseases, both with their native immune system and now with human-like defenses against specific pathogens.