The Populus PTD promoter imparts floral-predominant expression and enables high levels of floral-organ ablation in Populus,Nicotiana and Arabidopsis

We evaluated the utility of the promoter from the Populus PTD gene—homologous to the MADS box genes DEFICIENS and APETALA3—to genetically engineer reproductive sterility. Floral-predominant expression was confirmed via GUS reporter assays in two heterologous species (Arabidopsis and tobacco) and in an early-flowering poplar genotype. Using the PTD promoter to direct expression of the disarmed cytotoxin DTA resulted in sterile plants with otherwise normal growth at high frequency in all three species. Biomass production in greenhouse-grown, morphologically normal tobacco cytotoxin lines was indistinguishable from lines lacking the cytotoxin gene, confirming strong floral specificity of the promoter. These results suggest that the poplar PTD promoter may prove useful for transgene confinement without detrimental effects on yield.