Project description:Jasmonates are important phytohormones activating plant tolerance to biotic and abiotic stress, as well as different development processes. These responses are mediated by a conserved signalling pathway activated by different hormones in different plants: dinor-12-oxo-phytodienoic acid (dn-OPDA) isomers in bryophytes and lycophytes, and JA-Ile in most vascular plants. The final responses depend, in many cases, on the accumulation of secondary metabolites. To identify novel compounds regulated by the dn-OPDA pathway in Marchantia, untargeted metabolomic analyses were carried out in response to dn-OPDA-regulated stress. A novel group of molecules were identified as dn-OPDA-amino acid conjugates (dn-OPDA-aas), and its accumulation after wounding and herbivory confirmed by targeted metabolic profiling in Marchantia and all species in which we previously found dn-iso-OPDA. Mutants in GRETCHEN-HAGEN 3A (MpGH3A) failed to accumulate dn-OPDA-aa conjugates, and showed a constitutive activation of the OPDA pathway and increased resistance to herbivory. Our results show that dn-iso-OPDA bioactivity is reduced by conjugation with amino acids. Therefore, an apparent dichotomous role of jasmonate conjugation in land plants is highlighted: jasmonic acid (JA) conjugation with isoleucine (Ile) produce the bioactive JA-Ile in tracheophytes, whereas conjugation of dn-iso-OPDA with different amino acids disactivate the hormone in bryophytes and lycophytes.
Project description:Jasmonoyl-isoleucine regulates defence, growth and developmental responses in eudicots. Bryophyte genomes have conserved sequences for all JA-Ile signalling pathway components, but in contrast to higher plants, the bioactive hormone has not been identified. We show that the JA-Ile receptor COI1 is functionally conserved in the bryophyte Marchantia polymorpha, but responds to a different ligand. Although Marchantia plants neither synthesize nor respond to JA-Ile, loss-of-function Mpcoi1 mutants have phenotypic defects reminiscent of COI1-dependent functions in Arabidopsis. AtCOI1 functionally complements Mpcoi1 mutation and confers JA-Ile responsiveness on M. polymorpha, as does a single amino acid substitution in MpCOI1 that switches ligand specificity. Mass spectrometry quantification of cyclopentenone derivatives, bioactivity analysis and COI1-ligand interaction assays pinpointed two isomers of the JA-Ile precursor dinor-OPDA (dinor-cis-OPDA and dinor-iso-OPDA) as the natural MpCOI1 ligands. Our results identify the ancestral jasmonate, confirm the functional conservation of its signalling pathway, and show that JA-Ile and COI1 emergence in higher plants from their ancestral counterparts required co-evolution of hormone biosynthetic complexity and receptor specificity.
Project description:In plants, jasmonate signalling regulates a wide range of processes from growth and develop-ment to defence responses and thermotolerance. Bioactive jasmonates, such as JA, JA-Ile, OPDA and dn-OPDA, are derived from C18- and C16- fatty acids (FAs), which are found ubiquitously in the plant kingdom. Bryophytes also contain long chain C20- and C22- FAs (LCFAs), which are absent in most vascular plants but are found in organisms of other king-doms, including mammals. The existence of bioactive jasmonates derived from LCFAs is cur-rently unknown. Here, we describe the identification of an OPDA-like molecule derived from a C20-FA in Marchantia polymorpha, which we term C20-OPDA. This molecule accumulates upon wounding, and when applied exogenously can activate known COI1-dependent and -independent jasmonate responses. Furthermore, we identify a dn-OPDA-like molecule (Δ4-dn-OPDA) deriving from C20-OPDA and demonstrate it to be a ligand of the jasmonate co-receptor (MpCOI1-MpJAZ) in Marchantia. By analysing mutants involved in the production of LCFAs, we elucidate the major biosynthetic pathway of C20-OPDA and Δ4-dn-OPDA. Moreover, using a double mutant compromised in the production of both Δ4-dn-OPDA and dn-OPDA, we demonstrate the additive nature of these molecules in the activation of jasmonate responses. Taken together, our data identify LCFAs as a source of bioactive jasmonates that are essential to plant plasticity and resilience.
Project description:In plants, jasmonate signalling regulates a wide range of processes from growth and develop-ment to defence responses and thermotolerance. Bioactive jasmonates, such as JA, JA-Ile, OPDA and dn-OPDA, are derived from C18- and C16- fatty acids (FAs), which are found ubiquitously in the plant kingdom. Bryophytes also contain long chain C20- and C22- FAs (LCFAs), which are absent in most vascular plants but are found in organisms of other king-doms, including mammals. The existence of bioactive jasmonates derived from LCFAs is cur-rently unknown. Here, we describe the identification of an OPDA-like molecule derived from a C20-FA in Marchantia polymorpha, which we term C20-OPDA. This molecule accumulates upon wounding, and when applied exogenously can activate known COI1-dependent and -independent jasmonate responses. Furthermore, we identify a dn-OPDA-like molecule (Δ4-dn-OPDA) deriving from C20-OPDA and demonstrate it to be a ligand of the jasmonate co-receptor (MpCOI1-MpJAZ) in Marchantia. By analysing mutants involved in the production of LCFAs, we elucidate the major biosynthetic pathway of C20-OPDA and Δ4-dn-OPDA. Moreover, using a double mutant compromised in the production of both Δ4-dn-OPDA and dn-OPDA, we demonstrate the additive nature of these molecules in the activation of jasmonate responses. Taken together, our data identify LCFAs as a source of bioactive jasmonates that are essential to plant plasticity and resilience.
Project description:Jasmonates are fatty acid derived hormones that regulate multiple aspects of plant development, growth and stress responses. Bioactive jasmonates differ between vascular plants and bryophytes (using jasmonoyl-L-isoleucine; JA-Ile and dinor-12-oxo-10,15(Z)-phytodienoic acid; dn-OPDA, respectively), but bind an evolutionarily conserved COI1 receptor. Whilst the biosynthetic pathways of JA-Ile in the model vascular plant Arabidopsis thaliana have been elucidated, the details of dn-OPDA biosynthesis in bryophytes are still unclear. Here, we identify an ortholog of Arabidopsis Fatty Acid Desaturase 5 (AtFAD5) in the model liverwort Marchantia polymorpha and show that FAD5 function is ancient and conserved between species separated by more than 450 million years of independent evolution. Similar to AtFAD5, MpFAD5 is required for the synthesis of 7Z-hexadecenoic acid. Consequently, in Mpfad5 mutants the hexadecanoic pathway is blocked, the dn-OPDA levels almost completely depleted and normal chloroplast development is impaired. Our results demonstrate that the main source of dn-OPDA in Marchantia is the hexadecanoic pathway and the contribution of the octadecanoid pathway, i.e. from OPDA, is minimal. Remarkably, despite extremely low levels of the bioactive hormone (dn-OPDA), MpCOI1-mediated responses to wounding and insect feeding can still be activated in Mpfad5 mutants, suggesting that dn-OPDA is not the only bioactive jasmonate and COI1 ligand in Marchantia.
Project description:JAZ genes are negative regulators of jasmonate responses with a dual function as repressors of transcription factors and co-receptors, together with COI1, of the hormone jasmonoyl-isoleucine (JA-Ile). This family has been mainly studied in angiosperms, where high gene redundancy hinders the characterization of a complete depletion of JAZ function. Moreover, the recent discovery that JA-Ile is not the sole COI1/JAZ ligand in land plants, as dn-OPDA is the bioactive ligand in Marchantia polymorpha, underscores the importance of studying JAZ co-receptors in bryophytes. Here we exploited the low gene redundancy of the liverwort Marchantia polymorpha to characterize the function of the single MpJAZ in this early-divergent plant lineage. We demonstrate that MpJAZ is the ortholog of AtJAZ and acts as a repressor of dinor-OPDA responses in Marchantia. Mpjaz mutants show a dwarf phenotype and severe developmental defects related to growth inhibition, consistent with a constitutive activation of the dinor-OPDA pathway and the overaccumulation of both dinor-OPDA and its precursor OPDA. The expression of AtJAZ3 in Mpjaz complements MpJAZ repressor function, indicating that JAZ function is conserved across land plants. However, AtJAZ3 is unable to form co-receptor complexes with MpCOI1 and dn-OPDA, which evidences that the Jas domain, and not only COI1, determines ligand specificity.
Project description:In the present study, Marchantia polymorpha Mppcs loss of function mutants were generated through CRISPR/cas9 mediated genome-editing. To assess whether the knockout of MpPCS gene affects the transcription of M. polymorpha nuclear genes in unstressed condition, the Mppcs-2 knockout mutant and Cam2 wild-type transcriptomes were compared by RNA-Seq.
Project description:In order to elucidate the role of the single Marchantia B-GATA ortholog in response to high light intensities, a transcriptomic analysis of Marchantia polymorpha BoGa, Mpb-gata1 mutants and MpB-GATA1ox under high-ligh stress conditions was performed.
Project description:RNA-seq of Marchantia polymorpha Mpb-gata1 mutants was performed in order to investigate their molecular signature of gene expression changes.