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Projects
Three | Intercellular protein trafficking through plasmodesmata.
This project is funded by the NSF-IBN
Integrative Plant Biology program.
The maize KNOTTED1 protein is able to traffic cell to cell, presumably
through plasmodesmata (PD), small channels that connect plant cells.
We have characterized this pathway using fusions to the green fluorescent
protein (GFP). We find that there are specific developmentally regulated
domains for protein trafficking. For example, a GFP~KN1 fusion protein
is able to traffic from perivascular cells through mesophyll and into
epidermal cells. However when expressed in the epidermis, the fusion
protein cannot traffic down into mesophyll cells. Remarkably, this
implies that there is directional regulation of protein trafficking
at the epidermal-mesophyll boundary. This appears to be a specific
property of GFP~KN1, since a fusion of GFP to a viral movement protein
is able to traffic from epidermal to mesophyll cells. Presumably this
reflects the virus’ ability to overcome the normal regulation
of PD trafficking in the leaf, which is necessary for the virus to
spread and cause infection.
 
We are particularly interested to understand how protein trafficking
is regulated in the shoot apical meristem. We therefore made specific
reporter constructs to allow us to drive the expression of any protein
in a restricted domain of the meristem. Using these reporters we have
found that GFP~KN1 is able to traffic bidirectionally in the meristem.
As protein trafficking appears to be an important regulatory mechanism
in plant development, we are developing these tools to understand
how trafficking is regulated in the meristem. In the future, these
tools will also be useful for the characterization of developmental
mutants that may affect protein trafficking or cell specification.
Our newer studies are aimed at defining trafficking signals in KN1,
and in developing genetic screens to characterize plasmodesmal trafficking.
  
Continue: Four | Localization of proteins of
unknown function in Arabidopsis.
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