外源蛋白在不同遗传背景、不同生长环境、不同发育时期和不同的组织类型下表达的稳定性是转基因作物性状稳定性的根本。为了评估基因型、生长地、发育阶段等因素对蛋白表达的影响，杜邦先锋公司的研究人员以玉米中的3个内源看家蛋白作为研究对象，系统分析了各种因素对其表达稳定性的影响。
看家蛋白参与了基本的细胞学过程，其表达相对来讲比较稳定，因此常作为内参对实验系统进行平衡化处理。研究不同环境下看家蛋白的表达变化能够间接反映出转基因作物中外源蛋白受基因型、生长地、发育阶段等因素的影响程度。研究人员在印度多个试验地点种植了一系列的杂交玉米材料，并连续两年通过ELISA实验测定了3个发育时期的叶片中3个看家蛋白的含量。这3个看家蛋白选自细胞骨架结构相关的Actin蛋白、氨基酸链延伸相关的EF1-alpha（Elongation Factor 1-alpha）蛋白和糖酵解途径中的GAPDH（glyceraldehyde 3-phosphate dehydrogenase）蛋白。结果表明，玉米内源蛋白的表达受到基因型的影响较小，而受到生长环境的影响较大。
该研究对于系统评估转基因作物的环境适应性和稳定性具有极大的借鉴意义。
Transgenic Research, 17 May 2018
Expression of endogenous proteins in maize hybrids in a multi-location field trial in India
Authors
Linga R. Gutha, Divakar Purushottam, Aruna Veeramachaneni……Jennifer Anderson*, Bonnie Hong, Jean Schmidt, Shveta Bagga
*: DuPont Pioneer, USA
Abstract
Genetically modified (GM) crops undergo large scale multi-location field trials to characterize agronomics, composition, and the concentration of newly expressed protein(s) [herein referred to as transgenic protein(s)]. The concentration of transgenic proteins in different plant tissues and across the developmental stages of the plant is considered in the safety assessment of GM crops. Reference or housekeeping proteins are expected to maintain a relatively stable expression pattern in healthy plants given their role in cellular functions. Understanding the effects of genotype, growth stage and location on the concentration of endogenous housekeeping proteins may provide insight into the contribution these factors could have on transgenic protein concentrations in GM crops. The concentrations of three endogenous proteins (actin, elongation factor 1-alpha, and glyceraldehyde 3-phosphate dehydrogenase) were measured in several different maize hybrids grown across multiple field locations over 2 years. Leaf samples were collected from healthy plants at three developmental stages across the growing seasons, and protein concentrations were quantified by indirect enzyme-linked immunosorbent assay (ELISA) for each protein. In general, the concentrations of these three endogenous proteins were relatively consistent across hybrid backgrounds, when compared within one growth stage and location (2–26%CV), whereas the concentrations of proteins in the same hybrid and growth stage across different locations were more variable (12–64%CV). In general, the protein concentrations in 2013 and 2014 show similar trends in variability. Some degree of variability in protein concentrations should be expected for both transgenic and endogenous plant-expressed proteins. In the case of GM crops, the potential variation in protein concentrations due to location effects is captured in the current model of multi-location field testing.
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