Recombinant monoclonal antibody yield in transgenic tobacco plants is affected by the wounding response via an ethylene dependent mechanism

Abstract

Variability in recombinant IgG yield in transgenic tobacco plants has previously been observed in relation to leaf position, and is interpreted as a function of ageing and the senescence process, leading to increasing protein degradation. Here, similar findings are demonstrated in plants of different ages, expressing IgG but not IgG-HDEL, an antibody form that accumulates within the endoplasmic reticulum. Antibody yields declined following wounding in young transgenic plants expressing IgG but not in those expressing IgG-HDEL. However, in mature IgG plants, the opposite was demonstrated, with significant boosts in yield, while mature IgG-HDEL plants could not be boosted. The lack of response in IgG-HDEL plants suggests that the changes induced by wounding occur post-translationally, and the findings might be explained by wounding responses that differ in plants according to their developmental stages. Plant mechanisms involved in senescence and wounding overlap to a significant degree and compounds such as ethylene, jasmonic acid and salicylic acid are important for mediating downstream effects. Treatment of transgenic plants with ethylene also resulted in a decrease in recombinant IgG yield, which was consistent with the finding that wounded plants could induce lower IgG yields in neighbouring non-wounded plants. Treatment with 1-MCP, an ethylene antagonist, abrogated the IgG yield drop that resulted from wounding, but had no effect on the more gradual IgG yield loss associated with increasing plant age.