Biology subjects

Garcia-Mina, J. M.

Publications and source records attributed to Garcia-Mina, J. M..

4 recordsLinked to original sources

bioRxiv2026

MpILR1 Hydrolyzes Jasmonate-Amino Acid Conjugates to Activate dn-iso-OPDA Signaling in Marchantia polymorpha.

Jasmonates are essential phytohormones that coordinate defense responses and developmental programs across land plants. In angiosperms, the active jasmonate ligand jasmonoyl-L-isoleucine (JA-Ile), is produced through GH3-mediated conjugation of jasmonic acid to isoleucine and JA-Ile homeostasis is further shaped by ILR1/ILL-family amidohydrolases. In contrast, the primary bioactive jasmonate ligand in bryophytes, dinor-12-oxo-phytodienoic acid (dn-iso-OPDA), is inactivated through conjugation with amino acids, raising the question of whether these conjugates constitute a reversible hormone reservoir or an irreversible catabolic end point. Although the ILR1-like family has been characterized extensively for its role in auxin and jasmonate homeostasis in angiosperms, its function in bryophytes remains basically unexplored. Here we show that MpILR1, the sole Marchantia ortholog of the ILR1/ILL family, hydrolyzes a specific subset of dn-iso-OPDA-amino acid conjugates in vivo. Loss-of-function Mpilr1 mutants exhibit enhanced accumulation of dn-iso-OPDA conjugated to hydrophobic amino acids (Val, Leu and Ile) but not to hydrophilic residues (His, Glu and Gln), demonstrating substrate-selective hydrolysis. MpILR1 hydrolytic activity is required for full dn-iso-OPDA-mediated responses, including transcriptional activation and defense against gastropod herbivory. These findings establish MpILR1 as a key positive regulator of jasmonate signaling in Marchantia polymorpha and suggest that hormone conjugation/deconjugation is an ancient regulatory mechanism evolved during plant terrestrialization.

plant biology↗

bioRxiv2024

Conjugation of dn-OPDA with amino acids inhibits its hormonal bioactivity in Marchantia polymorpha

Jasmonates are important phytohormones activating plant tolerance to biotic and abiotic stress, as well as different development processes. A conserved signalling pathway activated by distinct hormones in different plant species mediates these responses: 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 specialized 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 their 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, a 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.

plant biology↗

bioRxiv2021

An evolutionarily ancient Fatty Acid Desaturase is required for the synthesis of hexadecatrienoic acid, which is the main source of the bioactive jasmonate in Marchantia polymorpha

Jasmonates are fatty acid derived hormones that regulate multiple aspects of plant development, growth and stress responses. Bioactive jasmonates, defined as the ligands of the conserved COI1 receptor, differ between vascular plants and bryophytes (using jasmonoyl-L-isoleucine; JA-Ile and dinor-12-oxo-10,15(Z)-phytodienoic acid; dn-OPDA, respectively). 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 hexadecanoid pathway is blocked, 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 hexadecanoid pathway and the contribution of the octadecanoid pathway, i.e. from OPDA, is minimal. Remarkably, despite extremely low levels of dn-OPDA, MpCOI1-mediated responses to wounding and insect feeding can still be activated in Mpfad5, suggesting that dn-OPDA is not the only bioactive jasmonate and COI1 ligand in Marchantia.

plant biology↗

bioRxiv2020

Humic acids enrich the plant microbiota with bacterial candidates for the suppression of pathogens

Humic acids (HAs) stimulate the growth of several plant species by regulating their hormonal and redox metabolisms. Nevertheless, studies on the relationship of these substances with the plant-associated microbiota are almost nonexistent. Here, we hypothesized that the effect of HAs occurs in parallel with the regulation of the plant-associated bacterial community. Our results show the positive influence of HAs on the growth of rice and its stimulation of the root system. Metataxonomics revealed that the structure and composition of root bacterial communities were affected upon the application of HAs. Chitinophaga and Mucilaginibacter were the predominant genera in HA-treated roots. These bacteria produce enzymes that degrade compounds like those present in the wall of fungi, oomycetes, and nematode eggs. Pseudomonas and the Gp 1 group of Acidobacteria, both siderophore-producers and plant-growth promoters were also enriched, although with lower abundances. Given these results, we suggest that plants recruit these microorganisms in response to the stress caused by the HA-root interaction. For the first time, our findings indicate that HA-stimulated plants adopt the ecological strategy of recruiting members of the bacterial community that are candidates for the suppression of pathogens and, therefore, involved in plant defense.

microbiology↗