Transgenic maize plants expressing a fungal phytase gene

Abstract

Maize seeds are the major ingredient of commercial pig and poultry feed. Phosphorus in maize seeds exists predominantly in the form of phytate. Phytate phosphorus is not available to monogastric animals and phosphate supplementation is required for optimal animal growth. Undigested phytate in animal manure is considered a major source of phosphorus pollution to the environment from agricultural production. Microbial phytase produced by fermentation as a feed additive is widely used to manage the nutritional and environmental problems caused by phytate, but the approach is associated with production costs for the enzyme and requirement of special cares in feed processing and diet formulation. An alternative approach would be to produce plant seeds that contain high phytase activities. We have over-expressed Aspergillus niger phyA2 gene in maize seeds using a construct driven by the maize embryo-specific globulin-1 promoter. Low-copy-number transgenic lines with simple integration patterns were identified. Western-blot analysis showed that the maize-expressed phytase protein was smaller than that expressed in yeast, apparently due to different glycosylation. Phytase activity in transgenic maize seeds reached approximately 2,200 units per kg seed, about a 50-fold increase compared to non-transgenic maize seeds. The phytase expression was stable across four generations. The transgenic seeds germinated normally. Our results show that the phytase expression lines can be used for development of new maize hybrids to improve phosphorus availability and reduce the impact of animal production on the environment.

Nutritionally Enhanced Staple Food Crops

“…A thermotolerant phytase gene from Aspergillus has been used to alter phytic acid in maize, rice, and soybean (Table 3.10 ). For example, transgenic maize containing phyA2 gene showed a very high phytase activity (1791-2502 Unit kg À1 seed) and reduced phytic acid compared to WT (Chen et al 2008). Meanwhile, a MRP ATP-binding cassette transporter is highly expressed in embryo, and by silencing expression of this transporter, Shi et al (2007) produced transgenic maize low in seed phytate but high in Pi.…”

Producing Transgenic Thompson Seedless Grape (Vitis vinifera) Plants using Agrobacterium tumefaciens

“…The data indicated that leaves of transgenic plant leaves remained green, while leaves of control plants turned and became necrotic yellow, which indicating resistance and sensitivity to the herbicide, respectively. In other studies of the T2 generation it has been found that transgenic plants can express different responses to the herbicide, for example only 48 out of 65 transgenic seedlings of maize remained Basta resistant (Chen et al, 2008). Also for 130 explants in tobacco after selection with Basta herbicide subsequently only81 plants were Basta tolerant (62.30%) (Soliman et al, 2009).…”

“…Herbicide leaf painting assays: In order to evaluate the expression of bar gene, non-transformed (control) and putative transformed grape leaves were painted according to Chen et al (2008) with BASTA herbicide (a proprietary herbicide containing bialaphos) at a concentration of 2.0 g L -1…”

Iron Bioavailability of Maize Hemoglobin in a Caco-2 Cell Culture Model

“…The strategy of overexpressing ferritin received attention because plant ferritins have shown absorption as high as ferrous sulfate in rat models 16 and in humans. 17 It is now understood that ferritin is degraded during digestion and iron associated with the protein will enter the common nonheme iron pool, making it susceptible to phytate inhibition. 43 Unlike ferritin, hemoglobin has a unique uptake pathway and transport mechanisms, 44 and the heme pyrrole is protective against the inhibitory effects of phytate and other nonheme iron inhibitors.…”