CHARACTERIZATION OF CIS-ACTING ELEMENTS AFFECTING STRENGTH AND PHLOEMSPECIFICITY OF THE COCONUT FOLIAR DECAY VIRUS PROMOTER

During replication in its host plant, coconut foliar decay virus (CFDV ) remains restricted to the phloem tissue. Previous in vivo studies on subgenomic CFDV DNA had provided evidence for the phloem specificity of the CFDV promoter, Here, new promoter constructs are described whic h are distinguished by the presence or absence of various cis-acting s ignals and which gave rise to a 16-fold higher reporter gene (beta-glu curonidase) activity (reaching 30% of the cauliflower mosaic virus 35S promoter) in tobacco protoplasts, while the phloem specificity in tra nsgenic tobacco plants was conserved, Surprisingly, the CFDV stem-loop structure dramatically influenced transcriptional efficiency. From th ese studies and sequence comparisons with other phloem-specific promot ers, cia-signals involved in CFDV promoter strength and tissue specifi city were identified.