Aberrant promoter methylation occurred from multicopy transgene and SU(VAR)3 - 9 homolog 9 (SUVH9) gene in transgenic Nicotiana benthamiana

Abstract

The chemical modification of DNA by methylation is a heritable trait and can be subsequently reversed without altering the original DNA sequence. Methylation can reduce or silence gene expression and is a component of a host’s defence response to foreign nucleic acids. In our study, we employed a plant transformation strategy using Nicotiana benthamiana Domin to study the heritable stability of the introduced transgenes. Through the introduction of the cauliflower mosaic virus (CaMV) 35S promoter and the green fluorescent protein (GFP) reporter gene, we demonstrated that this introduced promoter often triggers a homology-dependent gene-silencing (HDGS) response. These spontaneous transgene-silencing phenomena are due to methylation of the CaMV 35S promoter CAAT box during transgenic plant growth. This process is catalysed by SU(VAR)3–9 homologue 9 (SUVH9), histone deacetylase 1 (HDA1) and domains rearranged methylase 2 (DRM2). In particular, we showed from our data that SUVH9 is the key regulator of methylation activity in epigenetically silenced GFP transgenic lines; therefore, our findings demonstrate that an introduced viral promoter and transgene can be subject to a homology-dependent gene-silencing mechanism that can downregulate its expression and negatively influence the heritable stability of the transgene.

Improving Pharmaceutical Protein Production in Oryza sativa

“…The main advantage of constitutive promoters is that they continuously express the gene in all parts of the plant. However, it was demonstrated that spontaneous transgene-silencing phenomena are caused by methylation of the CaMV 35S promoter during transgenic plant growth [74,75]. In addition, there is an increased chance of homology dependent gene silencing (HDGS) occurring.…”

Plant Based Bioreactors of Recombinant Cytokines (Review)

“…The main advantage of constitutive promoters is the constant gene expression in all parts of the plant. However, constitutive promoters have a low expression level and often undergo silencing as a result of methylation during transgenic plant growth [107]. Methods based on the use of inducible promoters are activated only under special conditions, and tissue-specific promoters working in certain plant organs became more widely used with the development of biotechnology.…”