In plantamonitoring of the activity of two constitutive promoters, CaMV 35S and TR2′, in developing feeding cells induced byGlobodera rostochiensisusing green fluorescent protein in combination with confocal laser scanning microscopy

Under the control of either the constitutive CaMV 35S or the mannopine synthase TR2′ promoter, the green fluorescent protein (GFP) from the jellyfishAequorea victoriawas expressed in transgenic potato (Solanum tuberosum) plants. Confocal laser scanning microscopy (CLSM) was applied to observe GFPin plantaand, subsequently, to investigate promoter activity in developing feeding cells developed during potato cyst nematode (Globodera rostochiensis) infection. Both the CaMV 35S and the TR2′ promoter were strongly upregulated in young feeding cells in less than 4 days upon infection byG. rostochiensis,whereas the GFP level in the surrounding tissues remained low. Optical sectioning revealed intense green fluorescence in the dense cytoplasm of the entire syncytial cell, including the most distal cell. Furthermore, GFP was observed within the digestive system of the feeding nematode, showing that proteins with an apparent molecular weight of 32 kDa can be taken up by parasitic juveniles ofG. rostochiensis. Provided CLSM is used, GFP was shown to be a powerful tool that allowsin vivomonitoring of gene expression inside young developing feeding cells. Finally, the transcriptional regulation of the CaMV 35S and TR2′ promoter in plant–nematode interactions is discussed.