Guo, Feng , McCubbin, Andrew G .
Petunia R-SNARE/Longin PiVAMP721 promotes vesicle fusion and is important in pollen tube growth.
Pollen tubes are an excellent model with which to study exo/endocytosis. The growing apex of these cells is dedicated to balancing these processes to form a cylindrical tube, and as a result perturbations of either exo- or endocytosis tend to cause a morphological phenotype. Membrane fusion is a key step during exo/endocytosis. VAMP7 is a SNARE protein that has been shown to mediate cognate membrane fusion. Human VAMP7 or Ti-VAMP is important in mediating neurite outgrowth. Here we present data that suggests PiVAMP721 of Petunia inflata is an important mediator of tip growth in pollen tubes. RT-PCR analysis suggests that PiVAMP721 is pollen specific, and phylogenetic analysis identifies AtVAMP725 is itís closest Arabidopsis homolog. Transient expression of an N-terminal YFP-PiVAMP721 fusion protein at low levels leads to labeling of the well-characterized inverted cone of vesicles at the pollen tube tip, as well as the plasma membrane. At high levels over-expression of this fusion protein inhibits pollen tube growth and causes bulging of the tips. Over-expression of the N-terminal longin domain alone has less effect, whereas the over-expression of C terminal domain of PiVAMP721 enhances the growth inhibition phenotype. Interestingly the bulging tips of these inhibited tubes developed large membranous sacs immediately behind the pollen tube tip. We hypothesize that PiVAMP721 is involved in an endocytic pathway important in pollen tube growth, either nutritionally or perhaps in the direct recycling of endocytic vesicles for tip extension.
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1 - Washington State University, School of Biological Sciences and Center of Reproductive Biology, Pullman, Wa, 99164-4236, USA
2 - Washington State University, School of Biological Sciences and Center of Reproductive Biology
pollen tube growth.
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM