The potato Lhca3.St.1 promoter confers high and stable transgene expression in chrysanthemum, in contrast to CaMV-based promoters

The enhanced cauliflower mosaic virus 35S (dCaMV) promoter and the potato Lhca3.St.1 promoter were evaluated for their expression abilities in chrysanthemum. The promoters were fused to the beta-glucuronidase (GUS) reporter gene with and without flanking matrix-associated regions (MARs). They were transferred into chrysanthemum via Agrobacterium-mediated transformation. The quantitative evaluation of GUS activity in a total of 127 independently derived transformants established that in chrysanthemum the Lhca3.St.1 promoter was 175 fold more active in the leaves than the dCaMV promoter was. The latter was as poor in expression as the single CaMV promoter. The use of such CaMV-based promoters in the genetic engineering of chrysanthemum should be discouraged when high levels of transgene expression are desired. No clear influence of the presence of MARs was observed on the variability of GUS gene expression, in contrast to earlier studies in tobacco. This may indicate a possible plant species dependent activity of MAR elements. Lhca3.St.1 promoter-driven GUS activity was relatively higher in the stem of chrysanthemum and proved stable over extensive time periods. Therefore this potato promoter is attractive to obtain high expression levels in chrysanthemum.