The growing world population has made the improvement of crop yield an important goal of agriculture. Conventional means for crop and horticultural improvements utilize selective breeding techniques to identify plants having desirable characteristics. However, such selective breeding techniques have several drawbacks, namely that these techniques are typically labor intensive and result in plants that often contain heterogeneous genetic components that may not always result in the desirable trait being passed on from parent plants. Yield has been considered a multi-genic trait for many decades. Some progress has been made to enhance yield by traditional plant breeding. Such methods involve crossing closely or distantly related individuals to produce a new crop variety or line with desirable properties. Plant biotechnology has helped improve crop yield by developing plants that are resistant to disease and pests. Additionally, transgenic herbicide resistant plants have helped to increase yield in crops.
The domestication of many plants has correlated with dramatic increases in yield. Most phenotypic variation occurring in natural populations is continuous and is effected by multiple gene influences. The identification of specific genes responsible for the dramatic differences in yield, in domesticated plants, has become an important focus of agricultural research. Seed yield is a particularly important trait since the seeds of many plants are important for human and animal nutrition. Crops such as, corn, rice, wheat, canola and soybean account for over half the total human caloric intake, whether through direct consumption of the seeds themselves or through consumption of meat products raised on processed seeds. They are also a source of sugars, oils and many kinds of metabolites used in industrial processes. Seeds contain an embryo (the source of new shoots and roots) and an endosperm (the source of nutrients for embryo growth during germination and during early growth of seedlings). The development of a seed involves many genes, and requires the transfer of metabolites from the roots, leaves and stems into the growing seed. The endosperm, in particular, assimilates the metabolic precursors of carbohydrates, oils and proteins and synthesizes them into storage macromolecules to fill out the grain. The ability to increase plant yield would have many applications in areas such as agriculture, including in the production of ornamental plants, arboriculture, horticulture and forestry. Increasing yield may also find use in the production of algae for use in bioreactors (for the biotechnological production of substances such as pharmaceuticals, antibodies or vaccines, or for the bioconversion of organic waste) and other such areas.
Mei2 is an important gene in promoting meiosis in Schizoacccharomyces pombe. The presence of mei2-like genes in plants was first revealed by the identification and characterization of Arabidopsis-mei2-Like1 (AML1). AML1 is expressed in a number of tissues including leaves, roots, flowers, and siliques. An mei2-like gene has been isolated from maize and called the TERMINAL EAR1 (TE1) gene. Upon characterization, the maize gene was indicated in plastochron and leaf initiation in the meristem by negatively regulating the number and position of the sites of leaf initiation. Studies have revealed that mei2-like genes are widespread in plants where they constitute a diversified group. A Mei2 is a protein containing three RNA recognition motifs (RRM), and is capable of binding to RNAs. Homologues of Mei2 have also been identified in plants.
Increasing yield in crops is of great important for agriculture. To develop cultivars of enhanced yield has been one of the most important targets for cultivar developments of various crops. Although progress has been made in crop yield improvement by traditional breeding, new methods of improving crop yield are still highly desirable to further improve yield for various crops. Therefore, methods are needed for increasing yield.
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