Deciphering the Possible Mechanism of GABA in Tobacco Pollen Tube Growth and Guidance.

gamma-Aminobutyric acid (GABA) is an inhibitory transmitter in animal central and peripheral nervous systems, and also plays an important role in pollen tube growth and guidance. However, the mechanisms underlying these effects in plants are poorly understood, mainly because the GABA receptor in plants has not been elucidated. To address this issue, we recently created quantum dot probes to identify possible GABA receptors on the membrane surfaces of pollen protoplasts. We found that GABA bound to cell membranes and regulated downstream Ca(2+) oscillation in the cells. These results provide important clues to further specifying the nature of the binding sites and deciphering the role of GABA as a signal molecule in pollen tube growth and orientation.