Abstract
During plant reproduction, sperm cells are delivered to ovules through growing pollen tubes. This process involves tip-localized receptor kinases regulating integrity and/or guidance of pollen tubes, whose localizations must be strictly regulated. However, the molecular basis for tip-localization of these molecules remains largely elusive. Here we show that a pair of AP180 N-terminal homology domain-containing proteins, PICALM5a and PICALM5b, is responsible for the tip-localization of ANXUR receptor kinases acting in an autocrine signaling pathway required for pollen tube integrity in Arabidopsis thaliana. The picalm5a picalm5b double mutant exhibits reduced fertility, and the double mutant pollen is defective in pollen tube integrity with premature bursts. The tip localization of ANXUR proteins is severely impaired in picalm5a picalm5b pollen tubes, whereas another receptor kinase PRK6 acting in pollen tube guidance is not affected. Based on these results, we propose that PICALM5 proteins serve as specific loading adaptors to recycle ANXUR proteins.
Highlights
During plant reproduction, sperm cells are delivered to ovules through growing pollen tubes
While none of wild-type pollen tubes burst 3 h after pollination (n = 35), 85.6 % of double mutant pollen tubes burst at this time point (n = 99) (Fig. 2e). These results indicate that PICALM5a and PICALM5b are required for pollen tube integrity, which is essential for fertilization in the basal part of the pistil
Our results suggest that PICALM5a and PICALM5b are required for tip-localization of ANX proteins, which could reflect the function of the PICALM5 proteins as loading adaptors for ANX proteins in clathrin-mediated endocytosis (CME)
Summary
Sperm cells are delivered to ovules through growing pollen tubes. We show that a pair of AP180 N-terminal homology domain-containing proteins, PICALM5a and PICALM5b, is responsible for the tip-localization of ANXUR receptor kinases acting in an autocrine signaling pathway required for pollen tube integrity in Arabidopsis thaliana. Phosphatidylinositol binding clathrin assembly protein 4a (PICALM4a) and PICALM4b (aka CAP1) have been shown to directly interact with TML, a core component of the TPLATE/TSET complex[7], and PICALM6/AP180 is shown to localize at the subapical plasma membrane in tobacco pollen tubes[8]. These results suggest that ANTH proteins have roles in plant endocytic processes. We report the essential roles of the redundantly functioning ANTH domain-containing proteins in tip-localization of ANXUR1/2 and sustained pollen tube integrity by probably acting as specific loading adaptors during CME
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
