VERNNATVAR_AT

Molecular analysis of the natural variation in vernalization response of Arabidopsis accessions

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 Obiettivo del progetto (Objective)

'The model plant A. thaliana shows a wide range of genetic and phenotypic variation among natural accessions. Notably, adaptation of flowering time to specific environmental conditions is essential for reproductive success. This proposal will use our knowledge of the molecular basis of vernalization to uncover how Arabidopsis thaliana accessions have adapted to their environment. Analysis of flowering time and vernalization in Arabidopsis accessions provides a unique opportunity to link mechanistic understanding of a complex trait with an understanding of the fitness consequences of different alleles and their distribution within the population. The specific aims of this project will be 1) to fully define the molecular variation at FLC and linked genes underpinning the natural variation in accessions selected to represent a wide range of vernalization responses and 2) use the different accessions as a pool of “natural mutants” to gain a better understanding of the basis of FLC regulation during vernalization. We will first confirm that FLC cis-elements are involved in this variation by a complementation analysis, followed by mix and match experiments to determine which region contains the cis-regulatory elements that account for the variation. We will also analyse the epigenetic changes at the FLC locus which result from the polymorphisms in the cis-elements, as well as the role of other chromosome 5 candidates identified in a QTL analysis for the variation in vernalization response. In parallel, we will characterize important cis-elements in FLC required to initiate and maintain FLC repression during and after vernalization. We will then pick natural variants with polymorphisms in these cis-elements. Dissecting the molecular basis of adaptation is a major goal in evolutionary genetics and the results from this study are likely to provide important insights into adaptation relevant to many biological systems.'

Introduzione (Teaser)

Plants need to be exposed to cold weather to be able to flower in season. Coldness, therefore, is a key factor in reproductive success for plant life. However, flowering can be speeded up by a process known as vernalisation. Knowing this, a project was launched to find out how a specific plant can adapt to its environment.

Descrizione progetto (Article)

The Arabidopsis thaliana, a plant native to Europe, Asia and North Africa, is a popular model organism used by biologists and geneticists because of its small plant genome. It is therefore regularly used to study flowering development.

A European project, entitled 'Molecular analysis of the natural variation in vernalisation response of Arabidopsis accessions' (Vernnatvar_at), studied plants' ability to flower or germinate in the spring by exposure to the prolonged cold of winter.

A. thaliana has a gene, called 'Flowering locus C' (FLC), which in normal temperatures prevents the plant from flowering. However, after a long cold winter, the gene is suppressed, and the plant is able to flower. Although, the gene has variations in its alleles - DNA sequences of a particular gene. In this case, they can allow the plant to either flower rapidly in one summer, or flower only after vernalisation.

The first test carried out by the project was to see whether FLC plays any role in the variation of vernalisation. A type of Arabidopsis thaliana from Sweden called Lov-1 was chosen as a test. The project showed that, after a relatively short vernalisation period, there was a delay in flowering.

Further tests on Lov-1 were carried out to determine what part of FLC contributed to the late flowering period. Results showed that a variation within FLC was responsible for the delay which allowed FLC to be activated, and thereby prevent flowering.

When delving deeper to discover why FLC had this variation, the researchers found that a specific histone (a protein that regulates genes) associated with repression plays a role: it does not successfully repress FLC to enable flowering in Lov-1. They found that the histone needs twice as much time to suppress FLC as it would in other genes.

The project, carried out under a Marie Curie Fellowship, successfully showed that variation within FLC contributes to the natural variation in Arabidopsis thaliana vernalisation.

Getting down to the molecular basis of local adaptation in plants is a major goal in genetics, which shows how successful the project was. Therefore, the results obtained from the study show how variation in vernalisation response will have broader impacts on the adaptation of many biological systems, not just Arabidopsis thaliana.