Seed-specific production

Seed-specific production of LTB by Streatfield et al. [28] resulted in expression levels of up to 1.8% total soluble protein (TSP), and two separate maize breeding programs have increased antigen production by fivefold [28] and tenfold [27]. The investigations of Chikwamba et al. [27] regarding the expression of LTB in maize are among the first to include the use of particle bombardment transformation for the production of plant-derived vaccines. 

Cereal expression systems are among the most advantageous for field-based recombinant protein production, since they combine intrinsic biosafety features (self-pollination in rice, barley and wheat, seed-specific protein expression) with practical ben-... 

Within each species, individual promoters resulted in distinct, tissue-dependent accumulation patterns. The cauliflower mosaic virus (CaMV) 35S promoter, for example, led to high-level accumulation in callus and leaves whereas the maize ubiqui-tin-1 promoter was the best choice for producing recombinant proteins in cereal seeds even though it is not in itself seed-specific [23]. The lack of such comparative studies for proteins other than rAbs makes it difficult to generalize an optimal expression strategy for all proteins. Tables 7.1 and 7.2 list recombinant proteins expressed in plants and provide details of the production system, promoters and other regulatory elements used in each case. 

Necessary seed types and quantities to achieve specific amounts of particle size increase in an all-growth process were calculated (Table 4-2) by a simple relationship relating seed and product size to the amount and particle size of seed to be added. Since the validity of this calculation depends on an all-growth process, simultaneous nucleation—which is virtually always present to some degree—will result in a reduction in the actual particle size of the product as well as an increase in the PSD. This increase often comes in the form of a bimodal... 

The highest ranked cell lines selected from the primary screens are then screened in 6-well plates using DM EM plus 10% FBS. Cells are seeded at 0.5 X 10 cells per well in duplicate and incubated for 4 days at 37 °C and 10% CO2. Culture supernatants are then harvested and the IgC concentration determined by Protein A HPLC or ELISA. Final cell concentrations are measured and the data used to calculate cell-specific production rates. The cell lines with the... 

A -desaturase genes were isolated from cyanobacteria and Borago officinalis. Introduction of these genes into tobacco under the control of the cauliflower mosaic virus 35S promoter resulted in y-linolenic acid (GLA) production in leaf lipids. The use of seed specific promoters also resulted in significant levels of GLA in seed lipids. 

Petrie, J. R. Shrestha, P Liu, Q. Mansour, M. P Wood, C. C. Zhou X.R. et al. rapid expression of trans-genes driven by seed-specific constructs in leaf tissue dHA production. Plant Methods 2010,6 8. 

Attempts to demonstrate the feasibility of profitable production on an agricultural scale are the next steps [282]. Poirier s group has proposed a number of oilseed crops that could be targeted for seed-specific PHA production, like rapeseed (closely related to A. thaliana), sunflower and soybean. Some of these are already under investigation by major companies. Depending on whether accumulation levels can be further increased PHAs stored in plants have any deleterious effects on crop value in other respects synthesis of PHAs other than PHB can be induced and extraction of the biopolyesters is feasible at reasonable costs, the cost of PHAs produced in plants might be lowered enough to make them competitive with conventional plastics. But the tendency of arable land to become one of the most precious commodities on Earth [286] will present a formidable obstacle to applications in this field. 

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