Screening for Transgenic Lines with Stable and Suitable Accumulation Levels of a Heterologous Protein

Genes encoding heterologous proteins are introduced into the plant genome for several purposes. First, the plant-made protein can be used as a tool in fundamental research. Reporter proteins can be used to characterize promoter sequences and other cis -acting sequences; the overproduction of proteins in plants can help to elucidate their function. Second, the synthesis of heterologous proteins in plants can have biotechnological applications. The introduced gene can confer new properties to the plant, or transgenic plants can be used as a source of important heterologous proteins. For all these purposes, the expression profile and accumulation level of the heterologous protein in plants should be stable, reproducible, and suitable. This chapter deals with the following problems∶ Most primary transformants show relatively low expression levels of the transgene (1 ); and expression levels are not always stably transmitted to the progeny.