Expression of the etr1-1 allele under control of floral- and senescence-specific promoters in Pelargonium zonale

In this study, two different etr1-1 allele-based expression constructs were introduced into Pelargonium zonale 'Katinka', controlled either by the senescence-associated gene 12 promoter (pSAG12) from Arabidopsis thaliana or by the floral-specific Petunia hybrida class B gene-specific promoter of FLORAL BINDING PROTEIN 1 (pFBP1). Selected kanamycin-resistant transgenic plants were transferred to the greenhouse, tested for expression of these transgenes, and further, the response of fresh flowers and fully expanded leaves to ethylene was studied. A reverse transcription (RT)-PCR revealed that the etr1-1 transcript from the FBP1 promoter construct was present in flowers, green tissues and roots, whereas the SAG12 promoter was only active in processes associated with premature ageing (senescence) in leaves and flower petals. Generally, the sensitivity to 2 µL L^‑1 of exogenous ethylene was markedly reduced by using both promoter constructs. Flowers from non-transformed controls had lost their vitality completely 96 h after ethylene exposure, while more than 90% of the flower petals from pFBP1::etr1-1 and more than half of the petals from pSAG12::etr1-1 lines remained unchanged. The leaves displayed less leaf yellowing and wilting, which were very similar for both promoter variants compared to wild-type controls.