"We have used quantum-dot bio-conjugates to uncover new knowledge about the binding of a protein at the growing pollen tube tip," researcher Cengiz Ozkan told nanotechweb.org. "This study not only opens the door for the potential use of quantum dots in live imaging of plant cells, but is also valuable for understanding the mechanism of interaction between the pollen tube and female tissue during reproduction."
Ozkan and colleagues used cadmium selenide (CdSe) quantum dots coated with zinc sulphide as fluorescent probes. The particles had a diameter of 6.3 nm. The team terminated the quantum dots with carboxylic groups by reacting them with mercaptoacetic acid. Then they conjugated the quantum dots with the amine groups of stigma/stylar cysteine-rich adhesin (SCA) - a plant pollen tube adhesion protein. This labelled the protein molecules with fluorescent tags.
The researchers then added the molecules to germinated lily pollen grains and examined them under a confocal microscope.
The team also imaged the proteins by conventional immunolocalization methods using fluorescently labelled antibodies.
"[We] learned from the quantum-dot labelling procedure that there were indications of endocytosis of the SCA into the pollen tube," said Ozkan. "The classical technique did not show any such result as its bulky size made endocytosis difficult."
A better understanding of the interaction of SCA with pollen tubes could help with successful plant breeding.
"Future work is focused towards further confirming the endocytosis of SCA inside the pollen tubes," said Ozkan. "This will be achieved by conducting similar localization experiments using a genetically engineered SCA that does not show the binding property to the pollen tube tips in in vitro experiments."
The researchers reported their work in Nanotechnology.