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Statistical analyses were performed using … Statistical analyses were performed using R v2.12.1 (www.r-project.org/) and Microsoft Office Excel 2007. Differences in the morphological traits of rice seeds and kernels between Nipponbare and each cultivar or mutant were determined using Welch’s t-test (p < 0.05). The fold changes of all cultivars and mutants were calculated by dividing by the mean value of Nipponbare. The differentially accumulated metabolites between a cultivar and Nipponbare and between a mutant and Nipponbare were detected using the LIMMA package (Smyth, 2004), which includes false discovery rate (FDR) correction for multiple testing (Benjamini and Hochberg, 1995). We identified metabolites with significant changes in metabolite levels (the log2-fold change > |1|) and the corresponding FDR-corrected p-values that were <0.05.<br />
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We used the log2-fold change matrix for HCA and MDS analysis. HCA was performed using Cluster 3.0 (de Hoon et al., 2004), and the results of HCA were visualized using Java TreeView v1.1.6 (http://jtreeview.sourceforge.net/). We applied Euclidean distance as similarity matrices for the metabolites and cultivars or mutants and the average linkage for clustering. Using Euclidean distance as implemented in the ‘cmdscale’ function of the R software, we performed MDS analysis, which tries to demonstrate the underlying structure of empirically acquired data. We also used the log2-fold change values for this analysis. log2-fold change values for this analysis.
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