Factors Affecting Nuclear Dynamics and Green Fluorescent Protein Targeting to the Nucleus in Arabidopsis thaliana Roots
We have previously described a novel marker protein comprising a translational fusion between GFP, an effective tobacco nuclear localization sequence (NLS), and the complete coding region of E. coli beta-glucuronidase (GUS) (1). This protein is efficiently targeted to the nuclei of transgenic Arabidopsis plants, and can be conveniently observed in vivo using confocal microscopy. Nuclear movement within the roots has been studied using time lapse analysis (2). To characterise the mechanism governing this movement, we applied drugs that affect tubulin and actin, metabolic inhibitors, and chemicals that alter the concentrations of divalent cations in the cell. Our results indicate that nuclear movement in Arabidopsis roots is energy-dependent, and involves actin but not tubulin. The concentration of magnesium ions seems to play a crucial role in the movement of the nuclei and targeting of GFP-NLS-GUS chimeric protein into the nucleus. In contrast, concentration of calcium ions did not affect neither nuclear dynamic nor GFP accumulation. We discuss these results in terms of some of the physiological processes occurring within the cell.
(1). Grebenok et al., Plant J. 11:573 (1997), 12:685 (1997); Chytilova et al., Ann. Bot. 83:645 (1999).
Elwira Sliwinska1,2, Georgina Lambert1 and David Galbraith1
1Department of Plant Sciences, University of Arizona,