Plant Pollen Sex Receptor Discovered

When a particle of plant pollen lands on a female flower, its journey is not done. The pollen, which typically contains two sperm cells and a sperm transport vehicle called the pollen tube cell, germinates in order to deliver a sperm to an egg, which is often located deep in the flower. Following chemical signals, the pollen tube cell grows in length toward the egg, sometimes extending several centimeters to reach its target. Researchers previously identified some of the chemical signals—typically peptides—used by the female flower to entice the pollen tube cell to grow in the right direction. But they’ve struggled to identify the receptor for the peptide lures. A team led by Hong-Ju Li and Wei-Cai Yang of the Chinese Academy of Sciences has now identified a receptor on pollen tube cells for the peptide love potion (Nature 2016, DOI: 10.1038/nature16975). Working in the model plant Arabidopsis thaliana, the team found three membrane-spanning kinases called MDIS1, MIK1, and MIK2 that work synergistically to sense a female peptide signal called LURE1. When the team used genetic and biochemical techniques to block reception of LURE1, the pollen tube cells had trouble reaching the egg and enabling fertilization.