Arabidopsis COBL10 is a male determinant of pollination
Sha Li^a,1, Fu-Rong Ge^a,1, Ming Xu^b,3, Xin-Ying Zhao^a, Guo-Qiang Huang^a, Anja Kombrink^c, Liang-Zi Zhou^a, Jia-Gang Wang^a, Sheila McCormick ^b, Xian Sheng Zhang^a,2, Yan Zhang^a,2

^a State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai’an 271018, Shandong, China.
^b Plant Gene Expression Center, University of California Berkeley and United States Agricultural Department, Albany, CA94710, USA.
^c Phytopathology, Wageningen University, 6708 PB Wageninge, The Netherlands.
¹ These authors contributed equally to this work.
² Corresponding author, email yzhang@sdau.edu.cn, zhangxs@sdau.edu.cn

³ Current address: College of Horticulture, Shenyang Agricultural University, Shenyang 110866, Liaoning, China.

Abstract
Successful reproduction of flowering plants requires constant communications between female tissues and growing pollen tubes. Female cells secrete molecules and peptides as nutrients or guidance cues for fast and directional tube growth, which are executed by dynamic changes of intracellular activities within pollen tubes. Compared to the extensive interests on female cues and intracellular activities of pollen tubes, there is little progress on internal machinery of pollen tubes that perceive female cues and interpret them into fast and directional growth. We show here that COBL10, a glycosylphosphatidylinositol (GPI)-anchored protein (GAP), is one component of this pollen tube internal machinery. Mutations at COBL10 caused gametophytic male sterility due to reduced growth in female transmitting tract and compromised directional sensing of pollen tubes. Deposition of apical pectin cap and cellulose microfibril was disrupted in cobl10 mutants. Localization of COBL10 at apical plasma membrane but not at intracellular punctates is critical for its function and relies on proper GPI processing and its C-terminal hydrophobic residues. GAPs are universal cell sensors in eukaryotes, especially during male-female communication. The role COBL10 plays in pollen-pistil interaction suggested an evolutionarily conserved paradigm during reproduction.