Green fluorescent protein targeted to the nucleus, a transgenic phenotype useful for studies in plant biology

We present a characterization of transgenic Arabidopsis thaliana (L.) Heynh. plants expressing a chimeric gene comprising the Green Fluorescent Protein (GFP) and β-glucuronidase (GUS) coding sequences, fused to an efficient nuclear localization signal (NLS). The transgenic plants accumulate the fusion protein in their nuclei, and this provides a novel phenotype, that of green-fluorescent nuclei. The fluorescent nuclei are readily observed using conventional epifluorescence and laser scanning confocal microscopy. We describe the use of this phenotype for in vivo studies of nuclear shape and movement, cell division, and for analysis of the transcriptional activities of constitutive and tissue-specific promoters. We propose that the phenotype of fluorescent nuclei will prove particularly valuable in histological, physiological and developmental studies of higher plants that require the facile observation of nuclei within living cells and in the absence of fixation or external staining.