P-303 - ACC as a potential signaling molecule in plant-microbe co-evolution

Microbes have coevolved with plants since they transitioned from water to land about 450 million years ago, most likely influencing plant evolution. We hypothesize that one key signaling molecule in this early evolutionary interaction is 1-Aminocyclopropane-1-carboxylate (ACC), the ethylene precursor in seed plants. In non-seed plants such as bryophytes, ethylene is produced via an unknown precursor, while ACC itself plays a role as a candidate signaling molecule independent of ethylene. Furthermore, some microorganisms can consume ACC as a carbon/nitrogen source. Here, we hypothesize that ACC also operates as a candidate plant-microbe interaction signaling molecule, playing an important role in plant land colonization. First, we aim to verify ACC secretion by bryophytes, using the evolutionary model liverwort Marchantia polymorpha and its mutant lines targeting the ACC metabolism. Further, in a pilot study, the microbiome of Marchantia was analyzed by amplicon sequencing to validate an optimal sampling strategy. The bacterial community showed no differences between different sampling methods, validating our approach. Members of the core microbiome belong to genera known as complex carbon degraders. A culture collection was built based on this preliminary information, setting the stage for future studies on the potential role of ACC as signaling molecule, as well as the role of ACC deaminase activity of the microbiome core members and their impact on early plant development.