The present invention relates generally to plant genetic engineering, and specifically to a method for producing genetically engineered plants characterized as having increased growth and yield.
For each plant species, there exists a wide discrepancy in plant growth due to environmental conditions. Under most conditions, the maximum growth potential of a plant is not realized. Plant breeding has demonstrated that a plant""s resources can be redirected to individual organs to enhance growth.
Genetic engineering of plants, which entails the isolation and manipulation of genetic material, e.g., DNA or RNA, and the subsequent introduction of that material into a plant or plant cells, has changed plant breeding and agriculture considerably over recent years. Increased crop food values, higher yields, feed value, reduced production costs, pest resistance, stress tolerance, drought resistance, the production of pharmaceuticals, chemicals and biological molecules as well as other beneficial traits are all potentially achievable through genetic engineering techniques.
The ability to manipulate gene expression provides a means of producing new characteristics in transformed plants. For example, the ability to increase the size of a plant""s root system would permit increased nutrient assimilation from the soil. Moreover, the ability to increase leaf growth would increase the capacity of a plant to assimilate solar energy. Obviously, the ability to control the growth of an entire plant, or specific target organs thereof would be very desirable.
The present invention is based on the discovery that increased growth and yield in plants can be achieved by elevating the level of cyclin expression.
In a first embodiment, the invention provides a method of producing a genetically modified plant characterized as having increased growth and yield as compared to a corresponding wild-type plant. The method comprises contacting plant cells with nucleic acid encoding a cyclin protein, wherein the nucleic acid is operably associated with a regulatory sequence, to obtain transformed plant cells; producing plants from the transformed plant cells; and selecting a plant exhibiting said increased yield. The cyclin-encoding nucleic acid preferably encodes the cyclin cyc1aAt.
In another embodiment, the invention provides a method of producing a plant characterized as having increased yield, the method comprising contacting a plant with an agent which elevates cyclin expression above cyclin expression in a plant not contacted with the agent. The agent may be a transcription factor or a chemical agent which induces an endogenous cyclin promoter or other chemically inducible promoter driving expression as the cyclin transgene.
The invention also provides plants, plant tissue and seeds produced by the methods of the invention.