Arabidopsis GH3.10 conjugates jasmonates.

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Jasmonates are key regulators of plant development and defense responses.
• Jasmonoyl-isoleucine (JA-Ile) is the canonical bioactive jasmonate in angiosperms, synthesized by JAR1 and GH3.10 in Arabidopsis thaliana.
• The fertility of gh3.10 jar1 knockout lines suggests other jasmonates or GH3 enzymes may play a role.

Purpose of the Study:

• To investigate the contribution of other jasmonates and GH3 enzymes to plant fertility regulation.
• To identify the complete set of enzymes responsible for JA-Ile biosynthesis in Arabidopsis.
• To explore the potential bioactivity of novel JA conjugates in the absence of JA-Ile.

Main Methods:

• Liquid chromatography-mass spectrometry (LC-MS) for jasmonate quantification.
• Non-targeted ex vivo metabolomics of Arabidopsis flower and leaf extracts.
• In vitro enzyme assays to determine the substrate specificity of recombinant GH3 enzymes.
• Jasmonate application experiments to assess bioactivity.

Main Results:

• JAR1 and GH3.10 were confirmed as the exclusive enzymes for JA-Ile biosynthesis in Arabidopsis.
• 12-hydroxy-JA was identified as the preferred substrate for GH3.10.
• Novel JA conjugates (JA-Gln, JA-Asn, JA-Glu) were identified in flowers and leaves, particularly in JA-Ile deficient lines.
• The aos gh3.10 jar1 mutant was generated as a tool to study JA-Gln bioactivity.

Conclusions:

• Arabidopsis thaliana relies solely on JAR1 and GH3.10 for JA-Ile production.
• Several JA conjugates are present and potentially bioactive in the absence of JA-Ile.
• The precise role of these JA conjugates in regulating plant fertility requires further investigation.