Metabolic Adaptation in Transplastomic Plants Massively Accumulating Recombinant Proteins

Julia Bally,Maya Belghazi,Claudette Job,Dominique Job,Vladimir N Uversky

doi:10.1371/journal.pone.0025289

Julia Bally, Maya Belghazi + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0025289

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Abstract

BackgroundRecombinant chloroplasts are endowed with an astonishing capacity to accumulate foreign proteins. However, knowledge about the impact on resident proteins of such high levels of recombinant protein accumulation is lacking.Methodology/Principal FindingsHere we used proteomics to characterize tobacco (Nicotiana tabacum) plastid transformants massively accumulating a p-hydroxyphenyl pyruvate dioxygenase (HPPD) or a green fluorescent protein (GFP). While under the conditions used no obvious modifications in plant phenotype could be observed, these proteins accumulated to even higher levels than ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), the most abundant protein on the planet. This accumulation occurred at the expense of a limited number of leaf proteins including Rubisco. In particular, enzymes involved in CO2 metabolism such as nuclear-encoded plastidial Calvin cycle enzymes and mitochondrial glycine decarboxylase were found to adjust their accumulation level to these novel physiological conditions.Conclusions/SignificanceThe results document how protein synthetic capacity is limited in plant cells. They may provide new avenues to evaluate possible bottlenecks in recombinant protein technology and to maintain plant fitness in future studies aiming at producing recombinant proteins of interest through chloroplast transformation.

Highlights

The genetic modification of the plastid genome recently emerged as an alternative to nuclear transformation in fundamental research, for example to understand the interactions between the chloroplast and nuclear genomes, and in applied research, as a system of transgene expression for high-added-value protein production
While under the conditions used no obvious modifications in plant phenotype could be observed, the accumulation level of the ribulose 1,5-bisphosphate carboxylase/ oxygenase (Rubisco) subunits, the most abundant protein complex in leaves, strongly dropped in correlation with massive accumulation of recombinant proteins [4]
The transgenic plants over accumulating the Pseudomonas fluorescens hydroxyphenyl pyruvate dioxygenase (HPPD) did not exhibit peculiar phenotypes under the growth conditions used despite the massive accumulation of the recombinant protein (Figure 1)

Summary

Introduction

The genetic modification of the plastid genome recently emerged as an alternative to nuclear transformation in fundamental research, for example to understand the interactions between the chloroplast and nuclear genomes, and in applied research, as a system of transgene expression for high-added-value protein production. While under the conditions used no obvious modifications in plant phenotype could be observed, the accumulation level of the ribulose 1,5-bisphosphate carboxylase/ oxygenase (Rubisco) subunits, the most abundant protein complex in leaves, strongly dropped in correlation with massive accumulation of recombinant proteins [4].

Results

Conclusion