High-level Expression of Basic Fibroblast Growth Factor in Transgenic Soybean Seeds and Characterization of its Biological Activity

Abstract

The glycinin G1 gene encodes a soybean seed storage protein accumulating at a high level. We have used the G1 promoter to confer seed-specific expression of human basic fibroblast growth factor (bFGF) in transgenic soybeans. The coding region of 18 kDa bFGF was fused to the promoter or promoter-signal peptide sequence of G1 gene, and transferred into soybean. Analysis of transgenic plants demonstrated that bFGF transcript or protein was confined to the seeds. The highest level of bFGF accumulation in the seeds reached up to 2.3% of total soluble protein. The soybean-derived bFGF was biologically active as confirmed by its mitogenic activity on Balb/c 3T3 cells, and exhibited other properties identical to native bFGF. We also observed a seed-specific expression of beta-glucuronidase driven by the G1 promoter. These results indicated that the G1 promoter contains essential cis-elements for seed-specific expression, and thus can be used for expression of pharmaceutical proteins in soybean seeds.

The use of legume seed for expression and storage of high value proteins

“…storage protein promoter such as glycinin G1 promoter (Meinke et al 1981), which was used to achieve levels in the order of 2.5-3% in soybean (Ding et al 2006;Moravec et al 2007), the promoter of the alpha subunit of beta-conglycinin yielding about 2.9 % of TSP of human growth hormone (Cunha et al 2011a). Similarly, the seed specific promoter USP (unknown seed protein) was used to produce scFv antibody that accumulated about 2% TSP in pea seed (Saalbach et al 2001).…”

Advancements in Transgenic Soy: From Field to Bedside

“…Human basic fibroblast growth factor (bFGF) is another high value therapeutic that has been expressed in soybean seeds [72]. This therapeutic was expressed under the control of the soybean seed specific G1 promoter and endogenous signal sequence from soybean.…”

Protein Expression Systems: Why Soybean Seeds?

“…Theoretically, expression of transgenic proteins in soybean seeds represents one of the most cost-efficient platforms, and recent work has demonstrated potential economic advantages. Presently we (Garg, et al, 2007;Piller, et al, 2005), and others (Cunha, et al, 2010;Ding, Huang, Wang, Sun, & Xiang, 2006;Moravec, Schmidt, Herman, & Woodford-Thomas, 2007;Qi, et al, 2010;Rao & Hildebrand, 2009;Wang, et al, 2009;Zeitlin, et al, 1998), have developed stable soybean lines that express 1% to 4% of their total soluble protein as the transgenic protein. Since soybean seeds are 40% protein by weight, an average sized seed weighing approximately 150 milligrams represents approximately 2.4 milligrams of transgenic protein per seed at 4% expression (Table 1).…”