EXPRESSION OF CHALCONE SYNTHASE GENES IN COLEOPTILES AND PRIMARY LEAVES OF SECALE-CEREALE L AFTER INDUCTION BY UV-RADIATION - EVIDENCE FOR A UV-PROTECTIVE ROLE OF THE COLEOPTILE

Four chalcone synthase (CHS; EC 2.3.1.74) clones from rye were isolate d and characterized. Two of these clones were used for analysis of CHS gene activities in response to ultraviolet and visible radiation in t he coleoptile and the primary leaf of the rye seedling. The time-depen dence of CHS gene activation and the spatial distribution of CHS were studied by investigation of enzyme activities and CHS mRNA levels, inc luding in situ RNA hybridization. In the primary leaf strong induction of CHS gene activity was localized in the epidermal layers and only m arginally found in the mesophyll. The coleoptile showed an even higher response to UV irradiation, but CHS gene activity was evenly distribu ted throughout the tissues. It is suggested that, in addition to its f unction as a mechanical protection for the primary leaf during seed ge rmination and seedling emergence through the soil, the coleoptile may also protect the emerging seedling from harmful radiation.