Abstract

Antibodies are key elements in routine immunological tests, having a long history in detection of plant pathogens due to their specificity, reliability and fast performance. Heavy chain-only antibodies (HCAbs), circulating in the blood of camels are IgG isotypes that lack the light (L) chains and the heavy (H) chain is depleted of the first constant domain (CH1). The HCAbs interact with the antigen by virtue of only one single variable domain, referred to as VHH or nanobody (Nb). Owing to their unique properties: nanometer scale size, robust structure, stable and soluble behaviour in aqueous solution, high affinity and specificity for only one cognate target, as well as a sustainable source, Nbs are an ideal research tool in plants. There are several rapid and robust techniques for isolating highly specific Nbs. Antigen-specific Nbs are selected from constructed nanobody libraries (immune, naïve, synthetic) and specific binders are retrieved by phage display, yeast display or ribosome display. Their small size, easy folding in monomeric units and the possibility to express Nbs in the cytosol, make them attractive for their application to engineer resistance against plant pathogens, and the effect of multiple Nbs combined by gene stacking to engineer plant resistance can be studied. We summarize the current methodologies for isolation and production of Nbs, their application in detection of plant pathogens and nanobody-mediated resistance against plant pathogens. In addition, we explore novel implementations of VHHs in agricultural research.

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