Chaibang, Adisorn , Johnson, Mark A .
Are pollen tube guidance signals species specific?
Pollen tube growth and guidance are precisely regulated to ensure successful fertilization. In Arabidopsis, the pollen tube germinates on the stigma, penetrates the stigmatic cell wall, enters the style, grows through the transmitting tract, turns toward an ovule, grows up an ovule funiculus, targets the micropyle, and bursts within a synergid cell. Each of these steps is carefully regulated and guided by floral cells. Importantly, these steps represent opportunities for female cells to scrutinize potential mates; at each step, appropriate pollen is guided, while foreign pollen may be blocked or left to wander. Very little is known about the mechanisms of pollen discrimination. To begin to understand the molecular basis for mate choice in flowering plants, we hand-pollinated Arabidopsis stigmas with pollen from closely related members of the Brassicaceae. We observed several incongruities in pollen tube growth and guidance that contribute to barriers to interspecific hybridization. Interestingly, the distance that pollen tubes traveled before growth or guidance defects were observed did not correlate with the phylogenetic distance between the two species. We also observed combinations in which pollen tubes were able to target Arabidopsis ovules, but did not stop growing and burst. These results suggest that pollen tube reception, when the female gametophyte signals the pollen tube to stop growing and release sperm, is an interspecific barrier in these crosses, and that the molecules that mediate this signaling interaction have diverged in these species combinations. As genomics resources develop for the Brassicaceae, this approach can be used to identify molecules that mediate these signaling events and function as gatekeepers to interspecific fertilization.
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1 - Brown University, Department of Molecular Biology, Cell Biology, and Biochemistry, 185 Olive St.
Box G-L160, Box G-L160, Providence, RI, 02912, USA
pollen tube guidance
pollen tube reception.
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM