The birds do it, the bees do it, and now researchers have discovered how plants can do it better. Published in the February 1 issue of Genes & Development, researchers have discovered that the presence of a potassium ion channel in pollen increases reproductive success.
During pollination, pollen grains land on the female stigma (the receptacle portion of the female reproductive organ)and begin the process of extending a long tube up the style, through the ovary and into the ovule. Once in the ovule, the pollen tube tip bursts and releases the sperm that will fertilize the female egg. However, because many pollen tubes grow towards only a few ovules, the process of pollen tube elongation becomes a race for reproductive survival.
Dr. Herve Sentenac and colleagues at the CNRS and INRA Centre de Versailles in France have discovered that the Arabidopsis gene, SPIK, encodes a potassium ion channel that is found specifically in pollen. Potassium ion channels play crucial roles in a variety of cellular processes in animals, including neural activity and heart contraction in humans, but this paper is the first report of a potassium channel in pollen.
The SPIK protein forms a pore through the pollen cell membrane that specifically allows the passage of potassium ions through to the cytoplasm, thereby regulating intracellular potassium levels. Dr. Sentenac and colleagues found that plant cells deficient in SPIK displayed markedly decreased pollen tube growth.
Using several different biochemical and genetic approaches, Dr. Sentenac and colleagues conclude that the SPIK potassium ion channel increases pollen competitive ability by facilitating the rapid elongation of the pollen tube, and therefore helps to ensure the reproductive success of pollen grain.