Fig. 1.

Evolution of phytomelatonin (MT). At the beginning of life on Earth, it is believed that MT was first produced by prokaryotes. During the early stages of evolution, the progenitor cells engulfed cyanobacteria and α-proteobacteria, evolving into mitochondrial and chloroplast-containing plant cells, which were able to produce MT. The MT receptors CAND2/PMTR1 were first originated in single-celled green algae, Coccomyxa subellipsoidea and Botryococcus braunii. Following plant acclimatization, the phytohormone pathways initiated and increased the ability of the plant to cope with biotic stresses with the aid of MT. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)