Jasmonic Acid Pathway in Plant Hormone Signaling

Jasmonic Acid Pathway

Overview

• A plant hormone signaling pathway involved in defense responses against biotic and abiotic stresses
• Plays a crucial role in plant immunity, growth, and development

Biosynthesis

• Jasmonic acid (JA) is derived from alpha-linolenic acid, an omega-3 fatty acid
• Conversion involves the octadecanoid pathway, which includes the following enzymes:
  1. Lipoxygenase (LOX)
  2. Allene oxide synthase (AOS)
  3. Allene oxide cyclase (AOC)
  4. OPDA reductase (OPR3)

Signaling Pathway

• JA is converted to its bioactive form, jasmonoyl-L-isoleucine (JA-Ile), by the enzyme JAR1
• JA-Ile binds to the COI1 receptor, a component of the SCF (Skp, Cullin, F-box) complex
• The SCF complex ubiquitinates and degrades JAZ (jasmonate ZIM-domain) repressors, allowing for the expression of JA-responsive genes

Functions

• Defense against herbivores and pathogens:
  • Regulates the production of defense compounds, such as alkaloids and terpenes
  • Activates the production of reactive oxygen species (ROS) to combat pathogens
• Wound response:
  • Triggers the expression of wound-responsive genes, leading to the formation of callus tissue
• Growth and development:
  • Regulates root growth, senescence, and flower development
  • Modulates the expression of genes involved in auxin and ethylene signaling

Interactions with Other Hormones

• Interacts with salicylic acid (SA) to regulate defense responses against pathogens
• Antagonizes the effects of ethylene, promoting plant growth and development
• Interacts with auxins to regulate root growth and development

Jasmonic Acid Pathway

Overview

• Crucial plant hormone signaling pathway for defense against biotic and abiotic stresses
• Involved in plant immunity, growth, and development

Biosynthesis

• Derived from alpha-linolenic acid, an omega-3 fatty acid
• Involves the octadecanoid pathway with enzymes:
  • Lipoxygenase (LOX)
  • Allene oxide synthase (AOS)
  • Allene oxide cyclase (AOC)
  • OPDA reductase (OPR3)

Signaling Pathway

• Jasmonic acid (JA) converted to jasmonoyl-L-isoleucine (JA-Ile) by JAR1
• JA-Ile binds to COI1 receptor, part of SCF complex
• SCF complex ubiquitinates and degrades JAZ repressors, allowing JA-responsive gene expression

Functions

• Defense against herbivores and pathogens:
  • Regulates defense compound production (alkaloids, terpenes)
  • Activates reactive oxygen species (ROS) against pathogens
• Wound response:
  • Triggers wound-responsive gene expression
  • Leads to callus tissue formation
• Growth and development:
  • Regulates root growth, senescence, and flower development
  • Modulates auxin and ethylene signaling gene expression

Interactions with Other Hormones

• Interacts with salicylic acid (SA) for defense against pathogens
• Antagonizes ethylene, promoting plant growth and development
• Interacts with auxins for root growth and development regulation

A plant hormone signaling pathway involved in defense responses against biotic and abiotic stresses, playing a crucial role in plant immunity, growth, and development.