Table 1.
Rice cultivars in study population belong to indica or japonica subspecies.
Figure 1.
RNA expression response to drought differs between rice cultivars.
Hierarchical clustering and heatmap of expression levels in leaves of rice plants grown under control conditions (c) or drought stress (d). The code below the heatmap indicates the line id (see Table 1) and the condition (blue: control = c, green: drought stress = d).
Figure 2.
Correlation of physiological data with candidate gene expression.
Annotation, primer (P), locus identifier of and correlation coefficients for candidate genes with significant (p<0.05) positive (blue) or negative (red) correlation of log-transformed expressions levels with physiological data under drought (d) or control (c) conditions. Data of 21 different cultivars with 2 to 3 replicates per cultivar and condition, 51 data pairs in total. Negative rank - mean scoring rank multiplied with -1; WUE - water use efficiency; yield - chlorophyll-a fluorescence yield; FWS - fresh weight shoot; DWS - dry weight shoot; FWT - total fresh weight; DWT - total dry weight. Sorted by LocusID.
Figure 3.
Expression of genes for aconitate hydratase (A), an AMP deaminase (B) and asparagine synthetase (C) correlated negatively with shoot dry weight.
Relative expression levels of genes and average shoot dry weight measured in rice cultivars in three independent experiments. The regression coefficient r for the linear regression of shoot dry weight against expression level is shown in the upper right corner.
Figure 4.
Expression of the fructose-1,6-bisphosphatase gene correlated with photosynthetic quantum yield.
Correlation of relative expression levels of genes coding for a cytosolic (A) and a plastidial (B) fructose-1,6-bisphosphatase with photosynthetic quantum yield of leaves measured after 18 days of growth under drought stress.
Figure 5.
Metabolite response to drought differs between rice cultivars.
Hierarchical clustering and heatmap of metabolite levels in leaves of rice plants grown under control conditions (c) or drought stress (d). Metabolite levels were normalised within an experiment by Z-transformation as indicated in Material and Methods. The code below the heatmap indicates the line id (see Table 1) and the condition (blue: control, green: drought stress).
Figure 6.
Correlation of physiological data with metabolite levels.
Correlation coefficients for selected metabolites with significant (p<0.05) positive (blue) or negative (red) correlation between log-transformed metabolite levels with physiological data under drought (d) or control (c) conditions. Data of 21 different cultivars grown in two experiments. Mean values of three to five replicates per cultivar and condition and experiment were correlated. Negative rank - mean scoring rank multiplied with -1; WUE – water use efficiency (g DW/g H2O per day); yield - chlorophyll-a fluorescence yield; FWS - fresh weight shoot [g]; DWS - dry weight shoot [g]; FWT - total fresh weight [g]; DWT - total dry weight [g].
Figure 7.
Levels of serine (A) threonine (B) and threonic acid (C) correlated negatively with shoot dry weight of rice plants under drought stress.
Average metabolite levels and average shoot dry weight of 20 rice cultivars from two independent experiments.
Figure 8.
High asparagine levels are predominantly found in cultivars with low water use efficiency.
Water use efficiency (g water per g final dry weight per day) of rice cultivars grown under control or drought conditions plotted against the relative asparagine level (Z score of log2 transformed values) in their leaves. The vertical reference lines indicate the average asparagine level of all samples minus (left) or plus (right) one standard deviation.
Figure 9.
Levels of galactaric acid (A), glucose (B) and MST 2482.9 (C) correlate positively with shoot dry weight of rice plants under drought stress.
Average metabolite levels and average shoot dry weight of 20 rice cultivars from two independent experiments.
Figure 10.
Principal component analysis (PCA) separated samples by treatment and genetic origin of rice cultivars.
PCA plots on normalised metabolite levels with PC1 and PC2 (A) separated samples of plants grown under control (c) and drought conditions (d). PC2 and PC3 (B) separated samples of indica (blue) and japonica cultivars (green). Numbers for cultivars see Table 1.