Fig. 2

Decomposition of combined drought-heat stress response relative to single stress responses. The ten major response groups of genes and metabolic masses found by linear modeling of transcriptomic and metabolomic data are arranged as a table according to the specificity of single stress responses (columns) and the interaction of single stress responses in combined stress (rows). Each response group consists of two subgroups: the up-regulation part and the down-regulation part. For each subgroup, an arrow code indicates the direction of regulation in the single stresses (D denotes drought, H denotes heat), and a + or - sign denotes a significant positive or negative interaction term (D:H), respectively, which describes the difference between the observed response to combined stress and the combined additive response to single stresses. In the “additive” response groups, there is no significant interaction term, in the “reduced” response groups, the interaction term counteracts the single stress regulation, and in the “enhanced:” response groups, the interaction term enhances the single stress regulation; the specific response group has no single stress regulation but significant interaction. Opposite regulation between drought and heat occurs only in rare cases and is discussed in the main text. For each group, the numbers of up- and down-regulated genes and masses as well as the top significantly enriched processes summarizing the abiotic stress response functions of up- and down-regulated genes are given. For full lists of genes and enriched GO terms and for classification of each variable, see Additional file 2