Imaging of subcellular compartments in companion cells and phloem parenchyma cells.

<p>(a, c-h) Fluorescent proteins observed in leaves from plants resulting from crosses between <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> plants and lines carrying fluorescent proteins targeted to different subcellular compartments. Overlay images, obtained by CLSM, with fluorescence signals shown in false colors; CFP is shown in green (a, c-h) and GFP, YFP or RFP in red (a, c-h) except in (b). Superimposed pixels are shown in yellow. (a) Observation of chloroplasts in the companion cells of a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> x <i>p35S</i>:<i>RbcS</i>:<i>YFP</i> plant (PP2-A1:CFP fluorescence is shown in green and RbcS:YFP in red). (b) Observation of the typical morphology of phloem cells of a <i>p35S</i>:<i>GFP</i>:<i>LTI6b</i> plant. GFP is shown in green and chloroplast autofluorescence is shown in red. Two types of phloem cells—companion cells and phloem parenchyma cells—were identified on the basis of plastid distribution (autofluorescence, shown in red). In these plants, GFP:LTI6b fluorescence (in green) could also be used to identify sieve elements. Phloem parenchyma cells are the largest cells and are located on the edge of the vasculature. Sieve elements lack chloroplasts. Companion cells display typical chloroplast alignments. (c) Observation of nuclei in the companion cells of a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> x <i>p35S</i>:<i>H2B</i>:<i>RFP</i> plant. Companion cells have square-like nuclei. (d) Observation of the endoplasmic reticulum in the companion cells of a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> x <i>p35S</i>:<i>ER</i>:<i>YFP</i> plant. In companion cells, the ER is found principally next to the plasma membrane and around the nucleus. On this image, the ER can also be seen in a sieve element aligned between two arrays of companion cells. (e) Observation of mitochondria in the companion cells of a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> x <i>p35S</i>:<i>COX4</i>:<i>GFP</i> plant. On this image, large numbers of mitochondria can be seen in the companion cells. (f) Observation of vacuoles in the companion cells of a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP x p35S</i>:<i>yTIP</i>:<i>YFP</i> plant. The image shows several vacuoles per companion cell. (g) Observation of actin network in the companion cells of a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> x <i>p35S</i>:<i>FABD2</i>:<i>GFP</i> plant. Thick actin bundles can be seen whereas thin actin filaments are barely detectable. (h) Observation of cortical microtubules in bent companion cells at a vein junction in a <i>pSUC2</i>:<i>PP2-A1</i>:<i>CFP</i> x <i>p35S</i>:<i>GFP</i>:<i>MBD</i> plant. Stars indicate the vacuoles. Scale bar = 5 μm.