DIVERSITY OF RHYTHMS

Analysis of natural-genetic variation controlling the timing of GIGANTEA expression in Arabidopsis

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 Obiettivo del progetto (Objective)

'The circadian clock regulates many physiological and developmental processes in plants. The GIGANTEA (GI) protein plays a major role in the clock mechanism and controls important clock outputs including photoperiodic flowering. GI expression follows a circadian rhythm, with a peak in the evening, and changes in the timing of GI expression have dramatic effects on biological programs such as flowering. Natural-genetic variation in the timing of circadian-clock-controlled-gene expression is important in the adaptation of plants to growth at different latitudes both in nature and in agriculture. This project proposes to identify the molecular basis of natural-genetic variation that causes differences in the timing of GI expression between accessions of Arabidopsis. The three major objectives are (1) to map QTL implicated in the control of GI expression (2) to isolate the gene underlying at least one of these QTL and thereby identify a new gene, or natural allele of a known gene, that alters the timing of GI expression (3) to initiate the functional characterization of the identified GI regulator. To reach these objectives 85 Arabidopsis accessions were originally transformed with a GI::Luciferase transgene and several of them showed differences in the timing of GI expression compared to the reference accession Col. Two of these lines were crossed with Col and study of the F2 progeny demonstrated wide variation in the timing of GI expression. The results support the feasibility of the objectives, and these populations will be used in this program to identify QTL. Training on the study of natural variation will take place at the Max Planck Institute in Cologne and will complement the researchers existing skills in molecular biology. The technical expertise gained, the materials generated in the project and the expertise in project management that will be obtained will assist the applicant in reaching his goal of starting an independent research group in his home country.'

Introduzione (Teaser)

A wide range of physiological and developmental processes in humans and plants are regulated by an internal time-keeping mechanism, the circadian clock.

Descrizione progetto (Article)

In plants, several genes and proteins have been identified as playing a role in the regulation of the circadian clock. However, the complex workings of this mechanism are still not fully understood. Various data indicate that the GIGANTEA (GI) protein has an important function in the regulation of plant development, even controlling outputs such as photoperiodic flowering. Expression of the GI protein follows a circadian rhythm, peaking in the evening.

The 'Analysis of natural-genetic variation controlling the timing of Gigantea expression in Arabidopsis' (Diversity of rhythms) project set out to identify regulators of GI expression. More specifically, the EU-funded research team hoped to identify the molecular basis bringing about differences in the timing of GI expression between Arabidopsis ecotypes (accessions). Researchers sought to achieve this using natural-genetic variation in accessions of Arabidopsis thaliana. This novel approach held potential for producing information on the processes that lead to variation in nature.

Project partners focused on mapping quantitative trait loci (QTL) in the control of GI expression and on isolating the gene of at least one of these QTL, with the aim of revealing the factors at play in changing the timing of GI expression. QTL are strands of DNA that contain or are linked to the genes underlying a quantitative trait. Another objective was to characterise the function of identified GI regulators.

Researchers transformed 85 Arabidopsis accessions with a GI::Luciferase transgene. Two lines crossed with Arabidopsis mutant line Columbia (Col) demonstrated major differences in the timing of GI expression. Another success was being able to detect QTL that explain variations of GI peak time between the ecotypes. Experimental data suggest that differences of GI expression in natural ecotypes are due to a varied and complex genetic basis.

Natural-genetic variation in gene expression as regulated by the timing of a plant's circadian clock is important for understanding how plants adapt to growth at different latitudes both in the wild and in agricultural practices.