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Volume 33, No 1, Jan 2023

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 33 Issue 1, January 2023: 71-79   |  Open Access


RALF signaling pathway activates MLO calcium channels to maintain pollen tube integrity

Qifei Gao1,2,† , Chao Wang1,† , Yasheng Xi1 , Qiaolin Shao1 , Congcong Hou2 , Legong Li2 , Sheng Luan1,*

1Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA, USA
2College of Life Sciences, Capital Normal University, Beijing, China
These authors contributed equally: Qifei Gao, Chao Wang
Correspondence: Sheng Luan(

Pollen tube tip growth requires intricate Ca2+ signaling. Recent studies have also identified rapid alkalization factor (RALF)-family peptides and their receptors as critical components for pollen tube tip growth and integrity. The functional relationship of RALF and calcium signaling modules remains largely unclear. Here we report that disruption of RALF signaling pathway abolished the cytosolic Ca2+ gradient in the pollen tube, indicating that Ca2+ signaling is downstream of the RALF signaling pathway. We identified MILDEW RESISTANCE LOCUS O (MLO) family proteins MLO1, 5, 9, 15, as Ca2+ channels required for Ca2+ influx and pollen tube integrity. We further reconstituted the biochemical pathway in which signaling via RALF and RALF receptors activated MLO1/5/9/15 calcium channels. Together, we conclude that RALF peptides derived from pollen tube bind to their receptors to establish pollen tube Ca2+ gradient through activation of the MLO channels. Our finding has thus provided a mechanistic link between the RALF signaling pathway and Ca2+ signaling in controlling pollen tube integrity and growth.


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