Molecular Analysis of the Cell Plate Forming Machinery 305
Fig. 2DRP1 and DRP2 act as tubulase and pinchase that control membrane tubulization
and vesiculation, respectively.A,CDRP1 (phragmoplastin) acts as a tubulase and forms
highly ordered spiral polymers on the surface of vesicles. Upon GTP hydrolysis, DRP1
provides mechanical force to convert vesicles in to tubular structures.B,DDRP2 (plant
dynamin) acts as a pinchase and forms a collar ring surrounding the junction region
between a budding endocytic vesicle and plasma membrane.EA long dumbbell-shaped
tubule observed at the nascent cell plate of tobacco BY-2 cells (Samuels et al. 1995). Note
that the tubule is coated with DRP1 tubulase.FThe pinching off of endocytic vesicles
from the plasma membrane is blocked in fruit flies with a temperature-sensitive muta-
tion at theshibirelocus that encodes dynamin (Koenig and Ikeda 1989). DYN1, dynamin
GTPase domain includes a GTP-binding motif (GXXXSGKS/T) and a dynamin signature.
DYN2, dynamin central region. PH, pleckstrin homology domain which binds to mem-
brane phospholipids such as PI-3-P and PI-4-P. GED, dynamin GTPase effector domain.
PRD, proline-rich domain which interacts with SH3-domain proteins
2
Tubulase and Pinchase at the Cell Plate
Since the characterization of soybean phragmoplastin (Gu and Verma
1995) andArabidopsisADL1 (Dombrowski and Raikhel 1995), many other
dynamin-related proteins (DRPs) have been studied in plants. They par-