ABSTRACT
Genes may be differentially regulated, leading to different mRNA transcript levels: between different tissues; at different developmental stages; in response to various environmental stimuli; or between genetically dissimilar individuals, e .g . mutant in contrast to wild-type plants . Differential screening is a method of identifying cloned DNA sequences homologous to differentially regulated genes . Early examples of such genes include the small subunit of ribulose-l, 5-bisphosphate carboxylase (Bedbrook et aI., 1980) and Cl-amylase (Rogers and Milliman, 1983) and, to date, several hundred plant genes have been identified.
