Fight to survive: Marchantia synthesizes newly identified metabolites in response to wounding

Plants sense and adjust to continuously changing environmental cues. Whether these cues are abiotic like temperature and light, or biotic like soil microorganisms, plant responses to all of them are centrally coordinated through phytohormones. The field of phytohormone research has come a long way since the beginning of the last century when “phytohormone” simply meant auxin (Kende and Zeevaart 1997). Besides a group of “classic” hormones—auxin, gibberellin, ethylene, cytokinin, and abscisic acid—the field currently includes an extended group of small-molecule phytohormones that regulate different aspects of plant life and that arose over the course of their evolution (Kende and Zeevaart 1997; Gasperini and Howe 2024).<br><br>In terms of signaling pathways, one of the best understood phytohormones is jasmonate (JA). In angiosperms, JA conjugated to isoleucine (JA-Ile) is a major regulator of biotic and abiotic plant stress responses as well as developmental pathways (Chini et al. 2016). It controls diverse processes, from the scent of jasmine flowers to the regulation of complex transcription networks (Chini et al. 2016; Howe et al. 2018). The wide range of responses tightly regulated by JAs is a result of increasing evolutionary complexity and redundancy in its regulatory pathway. While JAs were already present in the earliest land plants and while different plant lineages share JA basic signaling pathway characteristics, the starting molecule that activates the pathway is different for different species (Chini et al. 2023). The lineages that led to Marchantia polymorpha and Arabidopsis thaliana diverged 450 million years ago. While in bryophyte Marchantia, dinor-12-oxo-phytodienoic acid (dn-OPDA) is the activating JA; in angiosperm Arabidopsis, the JA-Ile conjugate acts as the activator (Fig).