218 A. Rose
Table 1Protein markers for the study of nuclear envelope dynamics in plant mitosis
Protein Description Reference
NMCP1 Carrot coiled-coil protein Masuda et al. 1997, 1999;
MAF1, WPPs Tomato WPP domain protein and Dixit and Cyr 2002; Gindullis
Arabidopsis homologs et al. 1999; Patel et al. 2004
RanGAP1 Arabidopsis Ran GTPase activating Jeong et al. 2005; Pay et al.
protein 2002; Rose and Meier 2001
LBR N-terminal targeting domain of Irons et al. 2003
mammalian lamin B receptor
gion of the daughter nuclei and circles the nuclei completely during telophase
(Masuda et al. 1999). Similar to animal lamins, NMCP1 is predicted to have
a primarily coiled-coil structure, making it the best candidate for a lamin-like
protein in plants.
MAF1 and RanGAP share a homologous targeting domain, the WPP do-
main (Rose and Meier 2001). This domain is responsible for targeting green
fluorescent protein fusions to the nuclear envelope during interphase (see
Fig. 4) and to the cell plate of the phragmoplast in cytokinesis (Jeong et al.
2005; Patel et al. 2004). Three homologs of MAF1 exist in Arabidopsis. In-
terestingly, they are differentially targeted to the nuclear envelope. Only two
members of the family, WPP1 and WPP2, concentrate at the nuclear enve-
lope in meristematic root cells while the third one, WPP3, does not. Their
targeting is abolished once the cells reach the zone of differentiation, but is
reestablished after inducing root tissue to form callus. The reduction of these
proteins in roots via RNAi is associated with reduced mitotic activity, func-
tionally linking WPP proteins to mitosis (Patel et al. 2004).
In addition to nuclear envelope proteins, the Golgi proteinN-acetyl-
glucosaminyl transferase (Nag) has been found to label the plant nuclear
Fig. 4 Arabidopsis RanGAP1 marks the nuclear envelope in tobacco BY-2 cells.aFluor-
escence of RanGAP1-GFP fusion protein transiently expressed in a BY-2 cell as imaged
with a laser scanning confocal microscope.bCorresponding transmitted light image.
NEnuclear envelope,Nunucleus,Nonucleolus,Cytcytoplasm,Va cvacuole