Periodic Reporting for period 1 - ETHYLUTION (Revealing the ancient plant ethylene biosynthesis and ACC signaling pathway)
Periodo di rendicontazione: 2023-09-01 al 2026-02-28
When ancestral plants colonized the land 450 million years ago, they needed to adapt to harsh environmental conditions when giving up their aquatic lifestyle. Perhaps this was one of the most impactful events during the evolutionary history of plants. We hypothesize that during this water-to-land transition, the volatile plant hormone ethylene became an important growth regulator to face terrestrial stressors. In fact, modern-day crops use ethylene to regulate stress responses, and perhaps ethylene served this role in pioneering land plants to cope with harsh conditions coinciding with this habitat transition. We previously showed that ethylene signaling was functionally assembled in ancestral Charophyte green algae, prior to land colonization. Now we question why and how early land plants produced ethylene. It is known that seed plants make ethylene using ACC as precursor. However, non-seed plants produce ethylene via a different unknown ethylene biosynthesis pathway, which we want to reveal using the liverwort Marchantia polymorpha, a model species representing early life on earth. We also question why non-seed plants make ACC, but not use it for ethylene synthesis. New studies revealed that ACC itself can act as a signaling molecule, independent from ethylene, by an unknown signaling pathway to regulate plant development. We also postulate that both the alternative ethylene biosynthesis and ACC signaling pathway might have an origin in ancient algae, prior to land colonization, and might be conserved in seed plants, possibly exerting important functions yet to be uncovered. Using functional genetics in representative species of algae and crops, we will unravel the importance and role of ACC and ethylene that allowed plants to thrive on earth.
In order to unravel the true ethylene biosynthesis pathway and reveal the ACC signaling pathway of non-seed plants and algae, we use the model species Marchantia polymorpha, a liverwort and a representative descent of early land plants.
To discover the unknown ethylene biosynthesis pathway, we have performed an EMS genetic screen and identified several mutants with an altered ethylene production capacity (ebm mutants). We have phenotyped these mutants, and are in the process of identifying the causal mutations by whole genome sequencing. We have also established metabolomics techniques to measure the intermediate compounds of this putative biosynthesis pathway, and we have performed isotope tracing experiments to track these intermediate metabolites in their path towards ethylene synthesis.
To uncover the ACC signaling pathway, we have characterized and sequenced the candidate ACC-insensitive (ain) mutants. We have also performed additional omics experiments, including transcriptomics, proteomics and metabolomics to uncover the biological processes and pathway regulated by ACC signaling. We are currently further validating the biological function of several candidate regulatory genes and involved pathways.
To discover the unknown ethylene biosynthesis pathway, we have performed an EMS genetic screen and identified several mutants with an altered ethylene production capacity (ebm mutants). We have phenotyped these mutants, and are in the process of identifying the causal mutations by whole genome sequencing. We have also established metabolomics techniques to measure the intermediate compounds of this putative biosynthesis pathway, and we have performed isotope tracing experiments to track these intermediate metabolites in their path towards ethylene synthesis.
To uncover the ACC signaling pathway, we have characterized and sequenced the candidate ACC-insensitive (ain) mutants. We have also performed additional omics experiments, including transcriptomics, proteomics and metabolomics to uncover the biological processes and pathway regulated by ACC signaling. We are currently further validating the biological function of several candidate regulatory genes and involved pathways.
In ETHYLUTION we have been working to uncover the unknown ethylene biosynthesis and ACC signaling pathways. We have been able to identify a candidate pathway and precursor metabolites that liverworts use to make ethylene. We have also revealed candidate pathways that are involved in ACC signaling in liverworts. In the following years we will validate these candidate pathways, and study their biological functionality in Marchantia polymorpha development and stress responses. We will also translate our findings to other plant species such as algae, to find the evolutionary origin of these pathways, and seed plants, to unravel the conservation of these pathways.