Cell strains and plant material
Suspension cultures of Vitis rupestris (Seibicke et al., 2002), and a transgenic cell line of V. vinifera ‘Chardonnay’, expressing the fluorescent actin marker GFP-AtFABD2 (Akaberi et al., 2018), were cultivated in liquid medium containing 4.3 g.L-1 Murashige and Skoog salts (Duchefa, Haarlem, The Netherlands), 30 gL-1 sucrose, 200 mg.L-1KH2PO4, 100 mg.L-1 inositol, 1 mg.L-1 thiamine, and 0.2 mg.L-1 2,4-dichlorophenoxy-acetic acid (2,4-D), pH 5.8. The cells were subcultured weekly, inoculating 6 ml of stationary cells into 30 ml of fresh medium in 100 ml Erlenmeyer flasks and incubated at 27°C in the dark at 150 rpm on a horizontal shaker (KS250 basic, IKA Labortechnik, Staufen, Germany). For cultivation of the transgenic actin marker line, the medium was supplemented with kanamycin (50 mg.L-1). Since aluminium readily partitions into inactive complexes at neutral pH, especially in complex media, the complex MS medium was replaced by a acidified (pH 4.5) sucrose solution complemented with 3 mM CaCl2 (Ikegawa et al. , 2000).
The Vitis vinifera ssp. sylvestris genotype ‘Hö29’, and the V. vinifera ssp. vinifera variety ‘Augster Weiss’ were cultivated and collected from the grapevine germplasm collection of the Botanical Garden of the Karlsruhe Institute of Technology.