Biosynthesis of gibberellin-related compounds modulates far-red light responses in the liverwort Marchantia polymorpha

The phytohormone gibberellins (GAs) are key regulators of growth, development and environmental responses in angiosperms. From an evolutionary perspective, all major steps of GA biosynthesis are conserved among vascular plants, while GA biosynthetic intermediates such as ent-kaurenoic acid (KA) are also produced by bryophytes. Here we show that in the liverwort Marchantia polymorpha, KA and GA12 are synthesized by evolutionarily conserved enzymes, which are required for developmental responses to far-red light (FR). Under FR-enriched conditions, mutants of various biosynthesis enzymes consistently altered thallus growth allometry, delayed the initiation of gametogenesis, and affected the morphology of gamete-bearing structures (gametangiophores). By chemical treatments and LC-MS/MS analyses, we confirmed these phenotypes were caused by deficiency of some GA-related compounds derived from KA, but not bioactive GAs from vascular plants. Transcriptome analysis showed that FR enrichment induced the up-regulation of genes related to stress responses and secondary metabolism in M. polymorpha, which was largely dependent on the biosynthesis of GA-related compounds. Due to the lack of the canonical GA receptors in bryophytes, we hypothesize that GA-related compounds are commonly synthesized in land plants but co-opted independently to regulate responses to light quality change in different lineages during the past 450 million years of evolution.