DIFFERENTIAL USAGE OF PHOTORECEPTORS FOR CHALCONE SYNTHASE GENE-EXPRESSION DURING PLANT DEVELOPMENT

Photoregulation of chalcone synthase (CHS) mRNA accumulation was analysed in parsley (Petroselinum crispum) and mustard (Sinapis alba) plants at different developmental stages. In both species, CHS mRNA accumulation in young etiolated seedlings was primarily under phytochrome control. In leaves of adult re-etiolated plants, a UV-B photoreceptor was predominantly involved in photocontrol. The reduced red light control in mature leaves was not due to the absence of immunoreactive phytochrome. The apparent dependence of photoreceptor usage on the developmental state of the cell or organism was in accordance with observations on the photoregulation of fusion constructs between CHS promoters from parsley or mustard and the beta-glucuronidase reporter gene (GUS). When tested in the parsley protoplast transient expression system, both constructs yielded the same type of photoregulation as observed for the endogenous CHS gene.