LSFM of transgenic alfalfa plants with actin filaments visualized by GFP-FABD2 marker (green). (A, Supplemental Video S6) Root growing in the light-sheet microscope before the application and (B, Supplemental Video S7) during the application of S. meliloti labeled by mRFP (magenta). C, After perfusion, S. meliloti attached to the root hairs. (D, Supplemental Video S8) Actin filaments in the control root hair and (E, Supplemental Video S9) in two root hairs with attached S. meliloti imaged for the period of 8 h. Bar = 50 µm (A–C), 10 µm (D, E). Imaging: (A–E) W Plan-Apochromat 20×/1.0 NA, 488 nm (for GFP excitation) and 561 nm (for mRFP excitation) at 4% and 2% of relative laser power level, respectively, BP505–545 and BP575–615 detection, light sheet thickness 4.52 µm, z-stacks of 0.48 µm/plane, encompassing the volume of 438.46 × 438.46 × 380.43 µm (x × y × z) in (A–C) and 313.02 × 159.71 × 153.12 µm (x × y × z) in (D and E).