| Abstract Detail
Reproductive biology Joly, Valentin [1], Matton, Daniel P. [2]. Plants’ secret words of love: rapid evolution of pollen-pistil recognition proteins drives reproductive isolation of wild potatoes. Gathering 196 species, wild potatoes (Solanum sect. Petota) are a striking example of plant diversification. Although they coexist sympatrically throughout all Latin America, and have the physiological ability to hybridize with close species, they display strong reproductive isolation barriers. Experiments carried out in our laboratory show that pollen-pistil interactions are the cornerstone of this isolation: in a heterospecific pistil, pollen tubes can be slowed down and/or their receptivity to female chemoattractive cues can be impaired. How is this so finely regulated? Most of plant sexual interactions described to date involve binding of pollinic receptors to female protein ligands expressed in various locations all along the pollen tube path in the pistil or vice versa. We hypothesize that rapid divergence of these reproductive proteins, driven by directional selective pressures, is the engine of interspecific isolation. This could especially take the form of species-specific aminoacid changes accumulating within binding sites, impairing mutual recognition in case of an interspecific cross. To identify candidate proteins, we used next-generation sequencing technologies to obtain transcriptomes from ovules, pistils and pollen tubes of four closely related Solanum species, and screened for coding sequences displaying a non-synonymous substitution rate (dN) greater than the synonymous one (dS), which is a commonly used, robust signature of directional selection. This approach, that had scarcely been applied to plants so far, led to us to identify a wide range of candidates including proteins similar to well-known key players of pollen-pistil interactions —such as the ovule-expressed FERONIA (FER) receptor kinase, stylar adhesion proteins or pollen tube calcium channels— but also totally uncharacterized proteins including several families of small secreted cysteine-rich proteins (CRPs). CRPs are of outstanding interest since they display a dual evolutive pattern, involving a highly conserved cysteine backbone delimitating blocks of extensively divergent aminoacids. Several CRPs were shown to control various aspects of pollen-pistil interactions in other species, especially stigmatic and ovular chemoattraction cues. Using KAPPA, a sequence search program we recently developed to detect these peculiar proteins, we identified new groups of solanaceous-specific CRPs undergoing rapid divergence between species. These are promising candidates as ligands of pollinic or style receptors. Our study points out that reproductive isolation relies on a coordinated set of pistil species-specific checkpoints that need to be successively “unlocked” by pollen tubes to achieve fertilization. Further functional characterization of these proteins paves the way to a better understanding of the speciation processes in action among wild potatoes. Log in to add this item to your schedule
Related Links: Research paper describing KAPPA, our bioinformatic tool dedicated to detection of CRPs.
1 - Université de Montréal, Département des Sciences biologiques, Institut de Recherche en Biologie Végétale, 4101, rue Sherbrooke Est - Local G308, Montréal, QC, H1X 2B2, Canada 2 - Université de Montréal, Département des Sciences biologiques, Institut de Recherche en Biologie Végétale, 4101, rue Sherbrooke Est - Local F345, Montréal, QC, H1X 2B2, Canada
Keywords: pollen-pistil interactions reproductive isolation interspecific barriers solanaceae conspecific pollen precedence pollen tube guidance speciation.
Presentation Type: Oral Paper:Papers for Topics Session: 2 Location: Salon 1/The Shaw Conference Centre Date: Monday, July 27th, 2015 Time: 8:15 AM Number: 2002 Abstract ID:135 Candidate for Awards:CSPB President's Award for Best Student Presentation,CSPB Travel Bursary |