Consequences of environmental modifications on Arabidopsis seed mucilage properties, diversity and ecophysiological function

Informations

Funding country

France

Acronym

CEMMU

URL

-

Start date

10/1/2014

End date

-

Budget

394,880 EUR

Fundings

Abstract

Climate change is predicted to have major effects on ecosystems and their biodiversity. To evaluate the consequences of climate change detailed studies are required to determine the genetic basis of natural variation in traits affecting population dynamics and structure, together with the assessment of how these are modified by environmental constraints. Mucilage is formed around the seeds of certain species when they are imbibed and is proposed to play a range of ecophysiological roles, including maintaining seed viability. In Arabidopsis, mucilage is formed of two structurally distinct layers; precisely how and why the two layers are generated is unknown. In a previous ANR-project, we characterised natural variation in the outer layer of mucilage. We demonstrated that natural variability exists in the physicochemical properties of the macromolecules and in the amount of polymers produced. Furthermore, variation in the properties of outer mucilage polysaccharides was correlated to environmental constraints. In effect, natural variants from regions with cold winters were correlated with an increased production of outer mucilage layer polysaccharides. Furthermore, our preliminary results indicate that less inner mucilage layer polymers are produced in seeds when the mother plant is grown at higher temperatures. The impact of temperature modifications on mucilage traits will be studied in more detail in the CEMMU project using variants with divergent outer mucilage characteristics. These data will contribute to the prediction of the impact of climate change on natural populations of Arabidopsis. To date, little is known about the macromolecular structure of the polymers forming the inner mucilage layer, as extraction of these biopolymers can only be achieved by hydrolysis of the polysaccharide constituents. Nuclear magnetic resonance (NMR) can, however, be used to analyse mucilage properties in situ. Natural variants with divergent outer mucilage traits will be studied in detail using low-field NMR. As well as describing variation in inner mucilage properties, the data obtained will enable potential links between variation in the two mucilage layers to be ascertained and help in our understanding of layer formation. Previously, using low-field NMR, we found that mucilage retains water and slows down its transfer to internal seed tissues. Here, we will test the hypothesis that the water-retention properties of mucilage maintain seed hydration, thereby allowing sufficient time for repair mechanisms to function and prolonging seed viability. To test this, the effect of hydration-dehydration cycles on DNA/protein repair and viability will be analysed in a range of Arabidopsis mucilage mutants. As well as contributing to our knowledge of the genetic basis of natural variation, the natural variants exhibiting extreme mucilage properties are an original resource for the identification of novel genes involved in mucilage production. We will exploit three of these natural Arabidopsis mutants to identify and characterise genes modulating mucilage viscosity or the formation of the inner mucilage layer. The primary objectives of CEMMU are (1) to describe the natural variation in the inner mucilage layer, (2) to determine directly the effect of temperature constraints on mucilage synthesis, (3) to analyse the role of mucilage in seed viability and how this is affected by environmental conditions during seed set and (4) to identify and functionally characterise three loci that influence mucilage diversity. The CEMMU project involves the collaboration of three partners whose complementary skills have already been successfully employed for seed mucilage studies, as demonstrated by six co-publications.