FIGURE 4.

Expression of VSFP2s from the Ubi-10 promoter and targeting to nuclear membrane in root cells.(A–D) When driven by the ubiquitin-10 promoter, the FRET pair in VSFP2.3 (mCerulean and citrine) produces strong and uniform signals at the plasma membrane of cells in the root maturation zone (A,B). When WPP is fused to the VSFP2.3 construct, fluorescence is highly concentrated at the nuclear membrane in cells of the maturation zone and in root hair cells (C,D, +WPP). (E–H) Similar results are obtained with VSFP2.4 under the control of the ubiquitin-10 promoter (FRET pair mCitrine and mKate2; E,F, plasma membrane; G,H, +WPP, nuclear membrane). The weaker plasma membrane fluorescence than nuclear fluorescence in (G) and (H) indicates that ONM targeting of the ubiquitin-10 promoter-driven VSFP2.4 is more specific than the RPS5 promoter-driven VSFP2.4 (Figure 7). Images shown are fluorescence wide field images acquired after focusing on the top cell layers of the root or the root hair. Each image was made using the respective excitation and emission wavelengths of the individual chromophores (see Figure 3 legend).