Journal Article

Tip-localized receptors control pollen tube growth and LURE sensing in Arabidopsis

Takeuchi, Hidenori, Higashiyama, Tetsuya

2016

Overview

Pollen-specific receptor-like kinase 6 (PRK6), which signals through the guanine nucleotide-exchange factors ROPGEFs, is required for sensing of the LURE1 attractant peptide in Arabidopsis thaliana , and functions together with other PRK family kinases; when introduced into the pollen tubes of the related species Capsella rubella , PRK6 could confer responsiveness to AtLURE1. Multiple pollen-tube receptors for LURE1 In flowering plants, the female gametophyte secretes chemoattractant peptides to guide pollen tube growth so that it delivers the immobile sperm to the ovule-enclosed female gametophyte. Two papers published in this issue of Nature report the identification of male pollen tube cell-surface receptors for one of these female attractants, LURE1, in the model plant Arabidopsis thaliana . Wei-Cai Yang and colleagues show that LURE1 is perceived by a receptor-like kinase complex, the heteromer MDIS1–MIK. Tetsuya Higashiyama and Hidenori Takeuchi report that pollen-specific receptor-like kinase 6 (PRK6) is required for sensing LURE1, and PRK6 acts together with other PRK family receptors. Both groups demonstrate that by engineering pollen tubes of the sister species Capsella rubella to express a component of the A. thaliana receptors — either MDIS1 or PRK6 — the reproductive isolation barrier between the two species is partially broken down. Directional control of tip-growing cells is essential for proper tissue organization and cell-to-cell communication in animals and plants 1 , 2 . In the sexual reproduction of flowering plants, the tip growth of the male gametophyte, the pollen tube, is precisely guided by female cues to achieve fertilization 3 . Several female-secreted peptides have recently been identified as species-specific attractants that directly control the direction of pollen tube growth 4 , 5 , 6 . However, the method by which pollen tubes precisely and promptly respond to the guidance signal from their own species is unknown. Here we show that tip-localized pollen-specific receptor-like kinase 6 (PRK6) with an extracellular leucine-rich repeat domain is an essential receptor for sensing of the LURE1 attractant peptide in Arabidopsis thaliana under semi- in-vivo conditions, and is important for ovule targeting in the pistil. PRK6 interacted with pollen-expressed ROPGEFs (Rho of plant guanine nucleotide-exchange factors), which are important for pollen tube growth through activation of the signalling switch Rho GTPase ROP1 (refs 7 , 8 ). PRK6 conferred responsiveness to AtLURE1 in pollen tubes of the related species Capsella rubella . Furthermore, our genetic and physiological data suggest that PRK6 signalling through ROPGEFs and sensing of AtLURE1 are achieved in cooperation with the other PRK family receptors, PRK1, PRK3 and PRK8. Notably, the tip-focused PRK6 accumulated asymmetrically towards an external AtLURE1 source before reorientation of pollen tube tip growth. These results demonstrate that PRK6 acts as a key membrane receptor for external AtLURE1 attractants, and recruits the core tip-growth machinery, including ROP signalling proteins. This work provides insights into the orchestration of efficient pollen tube growth and species-specific pollen tube attraction by multiple receptors during male–female communication.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/449/1736 / 631/449/2675 / 631/449/2679/2113 / Arabidopsis - genetics / Arabidopsis - metabolism / Arabidopsis - physiology / Arabidopsis Proteins - chemistry / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / Attractants / Capsella - genetics / Capsella - metabolism / Capsella - physiology / Females / Flowering plants / Flowers & plants / Germination / Growth / Growth (Plants) / GTP-Binding Proteins - metabolism / Humanities and Social Sciences / letter / Ligands / multidisciplinary / Mutation / Observations / Ovule - metabolism / Peptides / Phenotype / Phosphotransferases - chemistry / Phosphotransferases - genetics / Phosphotransferases - metabolism / Physiological aspects / Physiology / Plant reproduction / Pollen / Pollen Tube - genetics / Pollen Tube - growth & development / Pollen Tube - metabolism / Protein Structure, Tertiary / Protein-Serine-Threonine Kinases - genetics / Protein-Serine-Threonine Kinases - metabolism / Proteins / Receptors, Cell Surface - chemistry / Receptors, Cell Surface - genetics / Receptors, Cell Surface - metabolism / Reproduction / Science / Signal Transduction / Species Specificity / Studies