Time Bomb for Pollen Tubes: Peptide RALF-Mediated Signaling Xiaomin Peng, Shanshan Li, Hao Wang  Molecular Plant  Volume 11, Issue 4, Pages 518-520 (April 2018) DOI: 10.1016/j.molp.2018.02.010 Copyright © 2018 The Author Terms and Conditions

Figure 1 RALF-Mediated Signaling Regulates Pollen Tube Integrity in Plant Fertilization. Upon landing on the surface of a flower stigma, pollen germinates immediately and forms a pollen tube carrying two sperm cells to grow rapidly toward ovules deeply embedded in the flower. Small peptides RALF4/19 secreted by the pollen tube interact with receptor heteromers comprising BUPS1/2 and ANX1/2 that localize on the pollen tube plasma membrane. The peptide–receptor interactions sustain pollen tube integrity. However, when pollen tubes reach the contact interface of pollen tube–female gametophytes, RALF34 competitively binds with BUPS1/2 and ANX1/2 at nanomolar concentrations and immediately induces pollen tube burst and sperm discharge. In addition, RALF4/19 can physically bind with cell wall-associated LXR proteins to regulate pollen tube integrity via activating the ANX1/2-mediated downstream signal transduction pathway in pollen tubes. Molecular Plant 2018 11, 518-520DOI: (10.1016/j.molp.2018.02.010) Copyright © 2018 The Author Terms and Conditions