First published online April 10, 2009
Development 136, 904e (2009)
© The Company of Biologists Limited
Trafficking cellular insights from plant vascular development
In this issue of Development, two papers exploit the genetic
tractability of the model plant Arabidopsis thaliana to investigate
plant vascular development, and by doing so shed new light on processes that
are of general importance to multicellular life. In the first study (see
p. 1529), Naramoto et
al. investigate the role of VAN3 in the formation of a continuous leaf
vasculature and report that both its subcellular localisation and activity are
regulated by phosphoinositide (PI) signalling. VAN3 is an ARF
GTPase-activating (ARF-GAP) protein, a family of proteins that regulate
multiple cellular processes, including endocytosis and secretion, through
their roles in vesicle transport and protein trafficking. Consistent with it
functioning in the post-Golgi transport pathway, VAN3, the authors report,
localises to subdomains of the trans-Golgi network (TGN). Through genetic
interaction studies and yeast two-hybrid screening, they identify two novel
regulators of VAN3 localisation: CVP2, an inositol polyphosphate 5'
phosphatase, and VAN3-binding protein (VAB). CVP2, they show, regulates VAN3
localisation to the TGN by regulating cellular PI levels, whereas VAB helps to
recruit VAN3 to PI-enriched TGN subdomains. PIs also control the ARF-GAP
activity of VAN3, leading the researchers to propose that they have a dual
role in regulating the subcellular distribution and enzymatic activity of
VAN3. Future work should identify whether VAN3 is also involved in polar auxin
transport.
In the second study, Pascal Genschik and colleagues turned to
Arabidopsis development to shed light on the activity of the
ubiquitin protein ligase APC/C
(p. 1475), which is
important for DNA replication and cell division but which surprisingly remains
active in post-mitotic vertebrate cells, such as neurons. The researchers
report that APC/C also remains active in most post-mitotic
Arabidopsis cells, and that reduced APC/C activity in mutant plants
results in developmental defects. These defects include disturbed vein
patterning in the cotyledon (the first leaf of a germinating seed) and
increased vascular tissue, indicating that APC/C functions in vascular
development and organisation. Although the role of PIs in vesicular
trafficking and the post-mitotic functions of APC/C now await further
investigation, these two studies illustrate the power of diverse model systems
for biological research.
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Related articles in Development:
- The APC/C E3 ligase remains active in most post-mitotic Arabidopsis cells and is required for proper vasculature development and organization
- Katia Marrocco, Alexis Thomann, Yves Parmentier, Pascal Genschik, and Marie Claire Criqui
Development 2009 136: 1475-1485.
[Abstract]
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- Phosphoinositide-dependent regulation of VAN3 ARF-GAP localization and activity essential for vascular tissue continuity in plants
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Development 2009 136: 1529-1538.
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