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 CRT to monitor changes in ER stress levels. EGF content was increased significantly in the mature grain of homozygous offspring and PDI and CRT gene 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.

种子已经进化出可以储存蛋白质而不会立即降解它，并构成了重组蛋白质储存的理想组织。不幸的是，与其他异源表达系统相比，种子中重组蛋白的生产因产量低而受到影响。为了提高大麦中人表皮生长因子 (EGF) 的产量，发育中的谷物中的蛋白质汇源关系被调节为 EGF，而不是大麦储存蛋白。该EGF在 B-大麦醇溶蛋白和种子特异性燕麦球蛋白启动子的控制下，通过将 EGF 系杂交到缺乏 B-大麦醇溶蛋白储存蛋白合成的 Risø 56 突变体中，将基因引入。分析后代植物的 EGF 和大麦醇溶蛋白表达以及未折叠蛋白反应 (UPR) 基因PDI和CRT 的表达，以监测 ER 应激水平的变化。纯合子代成熟籽粒、PDI和CRT中EGF含量显着增加基因表达上调。我们首次在大麦中证明，用被移除基因启动子驱动的特定异源蛋白替换丰富的种子储存蛋白可以加速大麦谷物中特定异源蛋白的产生。