Arabidopsis COBRA‐LIKE 10, a GPI‐anchored protein, mediates directional growth of pollen tubes

Abstract

These authors contributed equally to this work. SUMMARYSuccessful reproduction of flowering plants requires constant communication 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 is executed by dynamic changes of intracellular activities within pollen tubes. Compared with the extensive interest in female cues and intracellular activities of pollen tubes, how female cues are sensed and interpreted intracellularly in pollen is poorly understood. We show here that COBL10, a glycosylphosphatidylinositol (GPI)-anchored protein, is one component of this pollen tube internal machinery. Mutations in COBL10 caused gametophytic male sterility due to reduced pollen tube growth and compromised directional sensing in the female transmitting tract. Deposition of the apical pectin cap and cellulose microfibrils was disrupted in cobl10 pollen tubes. Pollen tube localization of COBL10 at the apical plasma membrane is critical for its function and relies on proper GPI processing and its C-terminal hydrophobic residues. GPI-anchored proteins are widespread cell sensors in mammals, especially during egg-sperm communication. Our results that COBL10 is critical for directional growth of pollen tubes suggest that they play critical roles in cell-cell communications in plants.

Glycosylphosphatidylinositol (GPI) modification serves as a primary plasmodesmal targeting signal

“…6). Previously reported non-Pd GPI-APs with exclusive PM localization also did not show Pd enrichment (Debono et al, 2009;Zhang et al, 2011aZhang et al, , 2011bLi et al, 2013Li et al, , 2015. Together, these observations suggest that Pd exclusion mediated by a non-Pd ectodomain likely occurs prior to arrival at the PM and Pd, possibly at the level of vesicle sorting in Golgi membranes.…”

A mutation in the catalytic subunit of the glycosylphosphatidylinositol transamidase disrupts growth, fertility and stomata formation in Arabidopsis.

“…The loss of GPI anchoring is embryonic lethal in mammals and plants (Nozaki et al, 1999;Lalanne et al, 2004;Gillmor et al, 2005). In plants, GPI-APs are involved in various metabolic and developmental processes, including cellulose biosynthesis, callose metabolism, morphogenesis, and different aspects of reproduction (Schindelman et al, 2001;Lalanne et al, 2004;Gillmor et al, 2005;Levy et al, 2007;Capron et al, 2008;Simpson et al, 2009;Harpaz-Saad et al, 2011;Li et al, 2013;Cheung et al, 2014). Here, for the first time to our knowledge, we investigate the role of GPI-APs in stomata formation.…”

POLYPRENOL REDUCTASE2 Deficiency Is Lethal in Arabidopsis Due to Male Sterility

“…Even more interestingly, a gene encoding SKU5-SIMILAR18 (AT1G75790) protein possessing four potential N-glycosylation sites is coexpressed (TAIR) with ACYL-COA SYNTHETASE5, which is critical for pollen development and sporopollenin biosynthesis (Quilichini et al, 2015). Moreover, Dol deficiency might disturb the function of COBL10, a GPI-anchored protein that is a component of pollen tube internal machinery critical for normal pollen tube growth and directional sensing in the female transmitting tract (Li et al, 2013). In line with this, an essential role of Dol kinase (DOK) in pollen development and the pollen tube reception pathway (Lindner et al, 2015) has been described recently.…”