Figure 4.

Influence of At-DBF2 overexpression in sense and antisense orientations on stress tolerance. BY2 cells were transformed by A. tumefaciens with recombinant T-DNA vectors containing At-DBF2 driven by CaMV 35S RNA promoter, pBIN-35S-At-DBF2 (upper left and right sections in A or diamonds in B), the CaMV 35S promoter and terminator pBIN-35S-CaMVter (bottom left sections in A or triangles in B), or antisense At-DBF2 under the control of the CaMV 35S promoter pBIN-35S-ASAt-DBF2 (bottom right sections in A or circles in B). (A) Picture of same amounts of transgenic cells after 3 weeks of growth on solid medium supplemented with 300 mM NaCl, 25% PEG, 2 mM H₂O₂, or at 47°C (heat). (B) Growth of suspension cells in liquid medium. Upon stress, growth was measured as fresh weight and expressed as percentage of unstressed growth (control) (a). Stresses were applied after subculturing (= day 0) at indicated temperatures (e) and concentrations of NaCl (b), PEG (c), and H₂O₂ (f). For the cold shock (d), cells were maintained at 0°C for 2 days before the 2-week culture at 22°C. For each construction, data of three independent transgenic lines were pooled. To not overload the figure, SDs are not shown (maximum 15% of measured values). (C) Northern analysis of At-DBF2+TDBF2, kin1, and HSP17.6. Total RNAs were extracted from independent lines transformed with pBIN-35S-At-DBF2 (1) and (2), pBIN-35S-CaMVter (3), and pBIN-35S-ASAt-DBF2 (4). Drought was induced with 10% PEG treatment for 5 hr (stressed).