Quantitative PCR of stress genes
To validate involvement of the abovementioned signaling pathways in polyp bail-out, we conducted a second polyp bail-out experiment (experiment II) and collected RNA samples at finer temporal resolution (6-h intervals) for a qPCR assay. The same salinity-changing profile and morphological changes in corals were observed as in experiment I (data not shown). Among the 10 stress genes in our qPCR assay, three expression profiles were identified. For CASP8 and FAS genes, significant upregulation occurred during the first 12 h and remained relatively stable afterward (Fig. 3, profile I). A second expression profile was exhibited by FGF2, FGFR2, RHO, and the two MMPs genes. For these genes, little upregulation was seen in the first 6 h (2.5-fold on average) followed by a significant upregulation of over 40-fold from 6 h to 12 h. Another significant upregulation of 8.4-fold was identified from 12 h to 18 h, after which the gene expression stabilized (Fig. 3, profile II). While for the NFKB1, JNK, and XIAP genes, linear upregulation during the entire experimental period was detected (Fig. 3, profile III).