Abstract
The maize Emb5 is an abscisic acid–responsive gene which is specifically expressed in the late embryo during seed maturity. To further dissect and identify the elements specific for its embryo expression pattern, we investigated the activity of the − 1653 bp upstream of the “full-length” promoter region of this gene in transgenic Arabidopsis plants. We first confirmed that the “full-length” promoter could indeed drive the expression of β-glucuronidase reporter gene (GUS) in the transgenic Arabidopsis seed embryo. Subsequently, DNA fragments of ~ 500 bp in length were generated after a series of progressive deletions from positions − 1653 bp to − 1 bp relative to the transcriptional initiation site. These fragments were fused with GUS and introduced into Arabidopsis. Measurement of the GUS activity in the immature seeds isolated from the transgenic plants revealed that the region between positions − 523 bp and − 1 bp, namely ProEm-D, is absolutely required and sufficient for the temporal and embryo-specific expression of GUS with an activity comparable with the full-length Emb5 promoter in Arabidopsis. Therefore, our results clearly demonstrated that the 523 bp ProEm-D can replace the − 1653 bp Emb5 promoter to drive embryo-specific expression in Arabidopsis seed. Because of its small size and strong embryo-specific activity, it could become the promoter of choice in metabolic pathway engineering to transfer multiple genes for the production of valuable pharmaceutical products in seeds, such as polyunsaturated fatty acids found in fish oils, or pro-vitamin A where at least three transgenes are required to assemble the entire metabolic pathways.
Highlights
Using corn seeds to produce recombinant proteins for human consumption has many advantages, including low probability of contamination by human and animal endotoxins, relatively high protein yield, and low production cost
This maize-derived short yet strong promoter activity that is comparable with the fulllength promoter (1653 bp) could be used for seed-specific expression of genes of interest in monocots as well as in dicots
To determine the embryo-specific activity of the Emb5 promoter, we utilized the model plant Arabidopsis as a host to express the full-length as well as its 5′ deleted shorter DNA fragments, which were individually fused with the GUS reporter gene
Summary
Using corn seeds to produce recombinant proteins for human consumption has many advantages, including low probability of contamination by human and animal endotoxins, relatively high protein yield, and low production cost. As a eukaryote, corn presents a clear advantage compared with the E. coli expression platform in order to express genes. Key message A 523 bp DNA fragment was identified from Zea mays that can drive strong embryo-specific expression in Arabidopsis. Plant Mol Biol Rep (2021) 39:288–300 originated from eukaryotic organisms due to codon compatibility as well as to express those proteins that require post-translational modification Embryo-specific promoters are required to drive the expression of exogenous genes and production of certain proteins in seeds of corn. Only very few tissue-specific promoters, especially those embryo-specific, are available at present, limiting the utility of corn seeds in the biotechnology industry
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