Diversion dirigée du métabolisme cellulaire chez le tabac sauvage Nicotiana benthamiana utilisé comme hôte pour l'expression hétérologue de protéines d'intérêt clinique
|Advisor:||Michaud, Dominique; Sainsbury, Frank|
|Abstract:||Plant molecular farming is an affordable and safe alternative to conventional expression animal and microbial systems for the production of clinically-useful recombinant proteins. However, these proteins are often susceptible to degradation by endogenous proteases of the host plant cells. Several strategies have been described to counter degradation processes including the co-expression of companion protease inhibitors. Few data, however, were available describing how the host plant’s physiology, especially its developmental stage, could impact the expression and protection of a clinically useful heterologous protein. In this study, we assessed changes in the activity of cysteine and aspartate proteases in the widely adopted expression host Nicotiana benthamiana, as a function of leaf age. We demonstrate that the expression of a tomato cysteine protease inhibitor, SlCYS8, allows to increase by nearly 40% the total yield of a model protein, the blood-typing C5-1 monoclonal antibody, in young and mature leaves where proteolytic activities are lower. Our results, while promising in practice, highlighted on the other hand the complexity of biochemical processes involved and the relevance of developing additional strategies to boost recombinant protein accumulation in planta. Towards this end, a new approach based on a deliberate diversion of the host plant defense metabolism was explored. We show that an activation of the jasmonic acid pathway in leaves induces the production of stress-related proteins, including protease inhibitors of various functional classes; and a significant decrease in the content of RuBisCO, a major contaminant during the purification of recombinant proteins. Based on this we included in our transfection procedure a pretreatment of plants with methyl jasmonate, a volatile form of jasmonic acid. This pretreatment significantly reduced RuBisCO levels in leaves, concomitant with a more than twofold increase of C5-1 yield in mature leaves. Our data highlight, overall, the potential of manipulating the host plant’s defense metabolism to increase heterologous protein yields, in complement to current protein protection strategies involving the co-expression of recombinant protease inhibitors.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||23 April 2018|
|Collection:||Thèses et mémoires|
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