Natural variation in Arabidopsis thaliana as a tool for highlighting differential drought responses

Abstract

To test whether natural variation in Arabidopsis could be used to dissect out the genetic basis of responses to drought stress, we characterised a number of accessions. Most of the accessions belong to a core collection that was shown to maximise the genetic diversity captured for a given number of individual accessions in Arabidopsis thaliana. We measured total leaf area (TLA), Electrolyte Leakage (EL), Relative Water Content (RWC), and Cut Rosette Water Loss (CRWL) in control and mild water deficit conditions. A Principal Component Analysis revealed which traits explain most of the variation and showed that some accessions behave differently compared to the others in drought conditions, these included Ita-0, Cvi-0 and Shahdara. This study relied on genetic variation found naturally within the species, in which populations are assumed to be adapted to their environment. Overall, Arabidopsis thaliana showed interesting phenotypic variations in response to mild water deficit that can be exploited to identify genes and alleles important for this complex trait.

Figure 1. A Principal Component Analysis of control and stressed plants.

The 8 accessions from the central core-collection are in bold type. The Col-0 accession is indicated by a cross. 1A/Repartition of accessions on the first (PC1 and PC2 axis) and second PCA planes (PC3 and PC4 axis). PC1 explains 27% of the variation, PC2: 23%, PC3: 18% and PC4:7%. 1B/Plots of the first and the second PCA planes on correlation circles. The measured characters are indicated respectively for watered (c) and stress (s) plants: TLA = Total leaf area, EL = Electrolytes Leakage, RWC = Relative Water Content, WKA = Water Keeping Ability. TLAc and TLAs, WKAc and WKAs, RWCc and RWCs and MDRc and MDRs are plotted on the same area, on the circle of correlation corresponding to the first plane. The MDRc and MDRs are plotted on the same area, on the circle of correlation corresponding to the second plane.

Figure 2. Dendrogram of the upgma classification of the whole set of accessions, under watered and water deficit conditions.

The central core-collection accessions are in bold. The Col-0 accession is indicated by a cross.

Figure 3. Electrolyte Leakage (EL,%) in rosettes of 24 accessions of Arabidopsis thaliana, in watered (black bars) and water deficit (grey bars) conditions.

Vertical bars are SE at the 95% confidence level (n = 3). Accessions are ordered on the X-axis, from left to right, according to increased reduction in EL following water deficit. The central core-collection accessions are in bold. Col-0 is indicated by a cross. * indicates a statistically significant difference between control and water deficit conditions at 95% confidence level, determined with a non parametric test (Kruskall-Wallis).

Figure 4. Relative Water Content (RWC,%) in rosettes of 24 accessions of Arabidopsis thaliana, in watered (black bars) and water deficit (grey bars) conditions.

Vertical bars are SE at the 95% confidence level (n = 3). Accessions are ordered on the X-axis, from left to right, according to increased reduction in RWC following water deficit. The central core-collection accessions are in bold. Col-0 is indicated by a cross. * indicates a statistically significant difference between control and water deficit conditions at 95% confidence level, determined with a non parametric test (Kruskall-Wallis).

Figure 5. Rosettes Total Leaf Area (TLA, cm²) of 24 accessions of Arabidopsis thaliana, in watered (black bars) and water deficit (grey bars) conditions.

Vertical bars are SE at the 95% confidence level (n = 4). Accessions are ordered on the X-axis, from left to right, according to increased reduction in TLA following water deficit. The central core-collection accessions are in bold. Col-0 is indicated by a cross. * indicates a statistically significant difference between control and water deficit conditions at 95% confidence level, determined with a non parametric test (Kruskall-Wallis).

Figure 6. Cut Rosette Water Loss (CRWL, %) of 24 accessions of Arabidopsis thaliana, in watered (black bars) and water deficit (grey bars) conditions.

Vertical bars are SE at the 95% confidence level (n = 3). Accessions are ordered on the X-axis, from left to right, according to increased reduction of CRWL following water deficit. The central core-collection accessions are in bold. Col-0 is indicated by a cross. * indicates a statistically significant difference between control and water deficit conditions at 95% confidence level, determined with a non parametric test (Kruskall-Wallis).