Biotech Updates

Effects of Seed-Specific Gene Silencing of OsMRP5 Gene in Transgenic Rice

April 30, 2014

Artificial microRNA (amiRNA) technology is now being tapped as the possible new approach for the seed-specific gene silencing of the OsMRP5 rice gene in hopes of engineering Low Phytic acid (LPA) rice. Phytic acid (PA) is the major storage form of phosphorous (P) in cereal and legume seeds. However, it is poorly digested by humans and monogastric animals and is regarded as an anti-nutrient in food and feed. Transgenic rice with the mutated gene OsMRP5 were developed and resulted in seeds with reduced PA content. However, they also had reduced seed weight and viability. 

The effectiveness of the amiRNA technology for the seed specific down-regulation of OsMRP5 was evaluated based on changes of seed P content, composition, and the agronomic performance of transgenic lines. Seed PA contents were reduced by up to 71.9% in brown rice grains of transgenic plants compared to control plants. There were also no significant differences of plant height and number of tillers per plant observed between the trangenics and the control.

However, the down regulation of OsMRP5 also resulted in increased inorganic phosphorous (Pi) which is a known inhibitor to starch synthesis enzymes, in the seeds. This resulted in significantly lower seed weights compared to control plants, together with decreases in seed germination and seedling emergence. 

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