Modulation of Barley ( Hordeum vulgare L.) Grain Protein Sink-Source Relations Towards Human Epidermal Growth Factor Ins
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ORIGINAL PAPER
Modulation of Barley (Hordeum vulgare L.) Grain Protein Sink‑Source Relations Towards Human Epidermal Growth Factor Instead of B‑hordein Storage Protein Michael Panting1 · Inger Bæksted Holme1 · Jón Már Björnsson2 · Henrik Brinch‑Pedersen1 Accepted: 6 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Seeds have evolutionarily developed to store protein without immediately degrading it and constitute ideal tissues for recombinant protein storage. Unfortunately, the production of recombinant protein in seeds is compromised by low yield as compared to other heterologous expression systems. In order to improve the yield of the human epidermal growth factor (EGF) in barley, protein sink-source relations in the developing grain were modulated towards EGF instead of the barley storage protein. The EGF gene, under the control of a B-hordein and a seed-specific oat globulin promoter, was introduced by crossing EGF lines into the Risø 56 mutant deficient in B-hordein storage protein synthesis. Offspring plants were analysed for EGF and Hordein expression and for expression of the unfolded protein response (UPR) genes PDI and CRTto monitor changes in ER stress levels. EGF content was increased significantly in the mature grain of homozygous offspring and PDI and CRTgene expressions were upregulated. We demonstrate, for the first time in barley, that replacement of an abundant seed storage protein with a specific heterologous protein driven by the promoter of the removed gene can accelerate the production of a specific heterologous protein in barley grains. Keywords Barley heterologous expression · Molecular pharming · B-hordein · Human EGF · Unfolded protein response (UPR)
Introduction The production of non-native proteins or peptides in a host organism, the so-called heterologous expression system, is a common strategy for the production of increased amounts of a specific molecule. Utilization of the intrinsic systems of a host to express complex molecules in vivo is favourable compared to synthesizing them in vitro, which is often laborious or simply not possible. The production of recombinant proteins in plants is often cheap compared with other production systems like microbial or mammalian cell culture Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12033-020-00279-3) contains supplementary material, which is available to authorized users. * Henrik Brinch‑Pedersen [email protected] 1
Department of AgroEcology, Research Center Flakkebjerg, Aarhus University, 4200 Slagelse, Denmark
ORF Genetics, Vikurhvarf 7, IS‑203, Kopavogur, Iceland
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systems [1]. Once a stable plant line is produced, scaling up the production is easy. With the main exception of having a slightly different N-glycosylation pattern, plants facilitate many of the same post-translational modifications (PTMs) as mammalian cells [2, [3]. Also, plants offer a low risk of contamination with toxic compounds and human pathogens [4]. The bar
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