Project

Discipline

Reproductive isolation; Species barrier; Reproductive isolation; Evolution; Plant breeding; Pollinator-mediated selection; Floral signals; Pollen tube reception

Lead
Lay summary
Reproductive isolation is one of the main mechanisms for establishing and maintaining species barriers. Reproductive isolation is based on mechanisms that reduce the capacity of two (incipient) species to mate and sexually reproduce with each other. Reproductive isolation can be based both on external (ecological) or internal (molecular) factors. Therefore, it manifests itself on several different levels during reproduction, most importantly before (pre-zygotic) or after (postzygotic) formation of a zygote. Reproductive isolation has important impacts not only on evolutionary processes, but also on plant breeding and thus food security. One part of this project focuses on pollinator-mediated pre-zygotic isolation in plants. Such isolation can evolve when floral signals attract specific, distinct pollinators in two groups of plants, leading to reduced exchange of gametes between these two groups. To understand the evolution of such different signals, we will analyze pollinator-mediated selection on floral signals. In addition, the role of herbivores in the evolution of floral signals will be studied. To understand the molecular bases of differences in signals, both genetic and epigenetic effects will be investigated. In the second sub-project, the focus is on interactions immediately preceding fertilization. Here we will investigate the molecular mechanisms of pollen tube reception, for which the FERONIA (FER) receptor-like kinase plays key role by controlling the access of the pollen tube to the embryo sac. In the project, the role of FER in interspecific crossing barriers will be studied. In addition, further genes involved in pollen tube reception will be identified by genome-wide association studies. Collectively, this project will lead to novel insights into the mechanisms and evolution of reproductive isolation in plants, a key component for the understanding of diversification and economic use of plants.

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Last update: 21.02.2013

Active participation

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The Research Module “Plant Reproductive Isolation: from Mechanisms to Evolution” is proposed to become part of the SNF Research Training Program for Doctoral Students “Plant Sciences and Policy”. This program combines a PhD in Plant Sciences with a set of courses that will allow the PhD students involved to obtain skills and expertise for policy work.Plant reproductive isolation is a crucial component of plant evolution. Furthermore, it is essential to seed production, plant breeding, sustainable crop yields, and food security. This Research Module aims at gaining a better understanding of the molecular mechanisms, ecological consequences, and evolutionary significance of reproductive isolation at different levels. We will investigate the molecular nature and ecological significance of pre-pollination reproductive isolation, specifically the effect of a changing environment on pollinator-mediated selection in Subproject A, and the mechanism and evolutionary role of post-pollination crossing barriers in speciation processes in Subproject B. These projects involve approaches from diverse fields such as genomics, ecology, evolutionary biology, genetics, statistics, as well as cell and molecular biology and thus offer a unique opportunity for young scientists to obtain interdisciplinary training. Importantly, the two PIs, whose backgrounds are in evolutionary ecology (Schiestl) and molecular genetics (Grossniklaus), have ongoing successful collaborations, illustrating the power of combining approaches from distinct fields in a joint effort. The two proposed subprojects require the expertise from both partners and could not be performed by one group alone. Pollinators mediate reproductive success in many plants and can thus select for floral traits. Little is known, however, about the details of pollinator-mediated selection, partly because of the lack of experimental data. Here we propose to assess the speed and evolutionary impact of an experimentally manipulated pollinator environment. From a starting population of rapid cycling Brassica rapa with extremely short generation time, three treatment groups with 5 replicates of 20 individuals each will be formed randomly and will be successively exposed to three different pollination types (honey bees, flies, random hand pollination as control) in a flight cage during 15 generations. Reproductive success, floral traits, as well as phenotypic selection gradients will be assessed in the three treatment groups during and after the experiment using multivariate statistics. In addition, the combined effect of herbivores and pollinators, and the role of sensory preferences of the different pollinator insects for pollinator-mediated selection will be investigated. After the selection experiment, the plants will be investigated at the molecular level to identify selected genetic and possibly epigenetic changes. The results will help us to understand whether changing pollinators lead to altered selection and whether changed selection regimes cause a short-term evolutionary response in plants. Mechanisms of reproductive isolation are central to evolution because they determine the rate of genetic exchange between populations and ultimately contribute to speciation. To date, there is a lack of studies that examine the molecular basis of reproductive isolation and evolutionary processes that operate on the level of genes. Successful plant reproduction relies on manifold interactions between the male and female reproductive tissues. One of the last steps prior to double fertilization is pollen tube reception: after penetrating a synergid cell, the pollen tube arrests its growth, ruptures, and releases the two sperm cells. The Arabidopsis FERONIA (FER) receptor-like kinase is required for this process. Since some interspecific crosses phenocopy the fer mutant, FER likely plays a role in establishing reproductive barriers and mediates a species-specific interaction. The goal of this subproject is to investigate the role of such a cellular recognition process in the ecology and evolution of species boundaries, using a combination of approaches from evolutionary genomics and molecular genetics. We will investigate the selective forces that acted during the evolution of FER and identify new components of this post-pollination reproductive barrier using genome-wide association studies (GWAS) in Arabidopsis thaliana. We will test whether pre-pollination isolation also affects this post-pollination process to increase compatible mating outcomes by analyzing allele frequencies of the Brassica orthologs of FER and the new candidate loci indentified by GWAS in the control and pollinator-treatment Brassica populations of Subproject A.