Plant Molecular Biology 43: 419–428, 2000.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
The plantibody approach: expression of antibody genes in plants to
modulate plant metabolism or to obtain pathogen resistance
Geert De Jaeger, Chris De Wilde, Dominique Eeckhout, Esbjörn Fiers and Ann Depicker
Vakgroep Moleculaire Genetica, Departement Plantengenetica, Vlaams Interuniversitair Instituut voor Biotech-
nologie (VIB), Universiteit Gent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium (
author for correspondence;
Received 18 April 2000; accepted in revised form 18 May 2000
Key words: antibody production, gene inactivation, immunomodulation, phage display, plantibody, reducing
environment, single-chain variable fragment
Immunomodulation is a molecular technique that allows the interference with cellular metabolism or pathogen
infectivity by the ectopic expression of genes encoding antibodies or antibody fragments. In recent years, several
reports have proventhe value of this tool in plant research for modulation of phytohormoneactivity and for blocking
plant-pathogen infection. Efﬁcient application of the plantibody approach requires different levels of investigation.
First of all, methods have to be available to clone efﬁciently the genes coding for antibodies or antibody fragments
that bind the target antigen. Secondly, conditions to obtain high accumulation of antigen-binding antibodies and
antibody fragments in plants are being investigated and optimized. Thirdly, different strategies are being evaluated
to interfere with the function of the target molecule, thus enabling immunomodulation of metabolism or pathogen
infectivity. In the near future, optimized antibody gene isolation and expression, especially in reducing subcellular
environments, such as the cytosol and nucleus, should turn immunomodulation into a powerful and attractive tool
for gene inactivation, complementary to the classical antisense and co-suppression approaches.
The fast-moving ﬁeld of recombinant antibody engi-
neering and expression continuously opens up new
opportunities, not only for the medical sciences, but
also for applied and fundamental agronomic research.
Many reports describe how very efﬁciently transgenic
plants produce complete antibodies or antibody frag-
ments, such as Fab and single-chain variable (scFv)
fragments (Figure 1) (for a review, see De Wilde
et al., 1999). Antibodies or antibody fragments pro-
duced in plants are often referred to as ‘plantibodies’
and they can be exploited for ex planta applications
in the ﬁeld of molecular farming. After isolation and
puriﬁcation from the plant tissue, the antibodies or an-
tibody fragments can be used in industrial processes,
as diagnostic tools, for immunochromatography, or in
medical therapy (Figure 1). In addition, there is also
a growing interest for in planta applications. Here,
we describe a strategy, called immunomodulation, in
which antibodies or antibody fragments are produced
to modulate the function of a corresponding antigen.
As such, immunomodulation can be used to study the
function of the antigen or even of the epitope in plants,
to change agronomic traits, or to ‘immunize’ the plant
against pathogen infection (Figure 1). We highlight
recent accomplishments in the use of plantibodies
for immunomodulation. We comment on the progress
in the isolation of recombinant antibody sequences
and their expression in plants, and we propose future
benchmarks that will further stimulate the general ap-
plication of this promising engineering technology in
plant molecular biology and agronomic research.