An efficient floral dipping transformation method for the metal hyperaccumulator Noccaea caerulescens

Noccaea caerulescens is a metal hyperaccumulator plant species with the capacity to accumulate high concentrations of zinc (Zn), cadmium (Cd) and nickel (Ni). Several candidate genes have so far been associated with accumulation and tolerance of these metals, but gene function analysis has been cumbersome in the absence of an efficient stable plant transformation method for N. caerulescens. A previously identified mutation in the FLOWERING LOCUS C gene, conferring early flowering to the calamine accession St. Felix de Pallières, has been introgressed in the genetic background of five different genotypes, originating from the calamine populations Clough Wood (CLW) and Le Blémard (BLE), the ultramafic population Cira (CIR), and the non-metallicolous populations St. Baudille (SBD) and Werschmatt (WER). Agrobacterium tumefaciens mediated floral dipping transformation was employed in five introgression lines in these backgrounds and in Arabidopsis thaliana as control. Three introgression lines, of genetic backgrounds CLW, BLE and SBD, were successfully transformed, achieving an average transformation efficiency ≥ 0.29% for each background. A reproducible, stable transformation method based on floral dipping is presented here as an improvement on previously reported methods. The early flowering N. caerulescens flc mutation can be readily introgressed into different genetic backgrounds to facilitate genetic transformation studies, which is expected to provide a highly desired extra genetic tool to study gene function analysis in the metal hyperaccumulator N. caerulescens.