Fig. 2. Dipeptide production by stony corals under thermal stress.

(A to C) Volcano plots of M. capitata metabolites generated from positive ionization mode data when comparing ambient- and high-temperature treatments. Putative dipeptides are shown with the filled orange circles. RA at T3 had an adjusted P = 1 and is not marked on the plot. (D to F) Accumulation of dipeptides KQ, RV, and RA under heat stress. The P values are all <0.005 when comparing ambient T5 and heat-stressed T5 using Student’s t test. (G to I) The metabolites that showed accumulation under heat stress matched synthetic standards of KQ, RV, and RA dipeptides in retention time and MS² spectra.