Addition of a histone deacetylase inhibitor increases recombinant protein expression in Medicago truncatula cell cultures

Plant cell cultures are an attractive platform for the production of recombinant proteins. A major drawback, hindering the establishment of plant cell suspensions as an industrial platform, is the low product yield obtained thus far. Histone acetylation is associated with increased transcription levels, therefore it is expected that the use of histone deacetylase inhibitors would result in an increase in mRNA and protein levels. Here, this hypothesis was tested by adding a histone deacetylase inhibitor, suberanilohydroxamic acid (SAHA), to a cell line of the model legume Medicago truncatula expressing a recombinant human protein. Histone deacetylase inhibition by SAHA and histone acetylation levels were studied, and the effect of SAHA on gene expression and recombinant protein levels was assessed by digital PCR. SAHA addition effectively inhibited histone deacetylase activity resulting in increased histone acetylation. Higher levels of transgene expression and accumulation of the associated protein were observed. This is the first report describing histone deacetylase inhibitors as inducers of recombinant protein expression in plant cell suspensions as well as the use of digital PCR in these biological systems. This study paves the way for employing epigenetic strategies to improve the final yields of recombinant proteins produced by plant cell cultures.