Seed-specific promoter

The case of canola is extraordinary because of the very high level accumulations (50-fold) of leaf-type carotenoids in seeds when the gene was introduced under the seed-specific promoter, napin. The exalbuminous seeds of canola differ from those of genetically engineered rice cereal grains in that they have chloroplasts, which may explain the capacity for hyperaccumulation of carotenoids. 

Copper is an essential micronutrient required in the growth of both plants and animals. In humans, it helps in the production of blood haemoglobin. In plants, copper is an important component of proteins found in the enzymes that regulate the rate of many biochemical reactions in plants. Plants would not grow without the presence of these specific enzymes. Research projects show that copper promotes seed production and formation, plays an essential role in chlorophyll formation and is essential for proper enzyme activity, disease resistance and regulation of water in plants (Rehm and Schmitt, 2002). 

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. 

Based on previous experiments in tobacco and Arabidopsis, the USP promoter fragment we used was considered to be highly seed specific. However, thorough examination of the field-grown pea plants revealed some promoter activity in pollen, albeit 100-fold lower than the activity seen in seeds (Fig. 12.3). To test whether or not the pollen expression is restricted to pea, we also examined pollen from transgenic... 

OUWERKERK, P.B., MEMELINK, J., A G-box element from the Catharanthus rosues strictosidine synthase (Str) gene promoter confers seed-specific expression in transgenic tobacco plants. Mol. Gen. Genet., 1999,261, 635-643. 

Cytokinins also delay senescence and hence can be used to prolong the shelf life of fresh vegetable and cut flowers and to promote seed germination. Cytokinins appear to be involved with transfer RNA (t-RNA) and, therefore, they possibly play a role in regulating the incorporation of specific amino acids into proteins. 

The use of seed-specific promoters appears to be the most promising (see Table 6.1). Seeds are also an attractive choice for molecular farming because they can be transported and stored for downstream processing, without any significant loss of yield or quality of the recombinant protein. Several seed-specific promoters from dicotyledonous and monocotyledonous plants have been isolated and used for expression of recombinant proteins in rice [32, 33], com [34—36], barley [14], wheat [37], tobacco [13], and even Arabidopsis [38]. The yield of recombinant proteins in seeds can reach up to 45% of TSP, as was shown in... 

Other c(5-elements involved in ABA induced transcription are a seed-specific element which mediates induction by ABA of the Cl gene in maize endosperm [33], an element from the promoter of the C. plantagineum gene CDeT27-45 [60] and the TT motif (TTTCGTGT) from the DCS gene from carrot [43,86]. The TT motif can be viewed as an imperfect ABRE and two bZIP proteins that bind to the element have been cloned. 

Vigeolas, H., P. Waldeck, T. Zank, and P. Geigenberger. 2007. Increasing seed oil content in oilseed rape (Brassica napus L.) by over-expression of a yeast glycerol-3-phosphate dehydrogenase under the control of a seed-specific promoter. Plant Biotech. J. 5 431 441. 

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