Plant cell migration: Opportunities and Challenges

         Ravi Palanivelu, Department of Plant Sciences


                         Abstract:

Background

After a pollen grain lands on the female structure, it absorbs water
from these tissues and forms a pollen tube =97 a long polar process
that transports all of the cellular contents, including the sperm. 
Subsequently, pollen tubes deliver sperm after navigating past a
variety of cells, most likely with the help of attractive and
repulsive cues.  The variety and inaccessibility of these cells and
tissues has made it challenging to characterize the dynamics of
pollen tube migration and identification of guidance signals.

Results

I have developed an in vitro assay in the model plant Arabidopsis
thaliana to study pollen tube guidance to excised egg-bearing
structures called ovules.  Using this assay, I characterized the
dynamics of pollen tube responses, established that unfertilized A.
thaliana ovules emit diffusible, developmentally regulated, species-
specific attractants, and demonstrated that ovules penetrated by
pollen tubes rapidly release diffusible pollen tube repellents.

Future challenges

These results demonstrate that in vitro pollen tube guidance to
excised A. thaliana ovules efficiently recapitulates much of in vivo
pollen tube behaviour.  This assay thus offers an unprecedented
opportunity to understand the dynamic regulation of plant cell
migration.  However, high-throughput analysis of acquired time-lapse
images remain a technical hurdle that has to be overcome before this
assay can be employed in identifying the long-elusive attractant and
repellent cues.


Reference:  Palanivelu, R. & Preuss, D (2006).  BMC Plant Biology, 6:7.