(A-C) AtMUTEp:AtMUTE-YFP is exclusively expressed in Guard Mother Cells (GMCs). Expression of AtMUTEp:YFP-BZU2/ZmMUTE and AtMUTEp:YFP-BdMUTE is seen in GMCs and neighboring cells. (D-E) The fluorescence of AtMUTEp:YFP-BZU2/ZmMUTE-ΔC is only observed in GMCs, being located both in the nucleus and the cytoplasm. The fluorescence from AtMUTEp:YFP-BdMUTE-ΔC expression is seen mostly in GMCs. (F) Quantification of YFP-AtMUTE (N = 128), YFP-BZU2/ZmMUTE (N = 227), YFP-BdMUTE (N = 197), YFP-BZU2/ZmMUTE-ΔC (N = 355), and YFP-BdMUTE-ΔC (n = 613) expression in GMCs and in neighboring cells. Arabidopsis images from T2 cotyledons, 3.5 dag. Cell walls are counterstained with propidium iodide (red). Scale bars, 10 μm. dag, days after germination.