Transient Gene Expression in Plant Protoplasts

Transient expression of genes in plant protoplasts is a powerful tool in plant molecular biology that allows quick screening and analysis of engineered proteins prior to stable transformation. Although stably transformed plant material may be preferable in many instances, transformation and regeneration of plants is time-consuming, tedious, and requires plenty of space. Transient expression techniques enable measurement of gene expression, as well as analysis of protein stability and activity, very shortly after DNA uptake; therefore, a large number of samples can be analyzed in a short period of time. Moreover, most of the introduced plasmid DNA remains extra-chromosomal during the transient assay (1 ) and, consequently, gene activity is not biased by position effects, as observed in stably transformed plants. Because of its speed, convenience, and flexibility, transient gene expression has been widely used for analysis of promoter and regulatory elements involved in transcription and translation (2 –6 ), induction of gene expression by exogenous stimuli (7 ,8 ), and for verifying functionality of cloned genes or cDNAs.