Uncoupling High Light Responses from Singlet Oxygen Retrograde Signaling and Spatial-Temporal Systemic Acquired...

Area of Science:

• Plant Physiology
• Molecular Biology
• Stress Signaling

Background:

• Reactive oxygen species (ROS) signaling, including singlet oxygen ((1)O2), superoxide, and hydrogen peroxide, plays dual roles in plant stress responses, mediating cell death or acclimation.
• Complex interactions, both antagonistic and synergistic, exist within and between these ROS signaling pathways.
• Studying specific chloroplastic ROS signals is challenging, necessitating alternative experimental approaches to understand their roles in plant acclimation.

Purpose of the Study:

• To investigate the distinct signaling pathways involved in high light (HL) stress perception and systemic acquired acclimation (SAA).
• To differentiate between local perception of HL/ROS and the distal signaling required for SAA.
• To elucidate the roles of specific ROS, mutants (tapx, ex1/ex2, rbohD/F), and vascular connections in plant acclimation responses.

Main Methods:

• Utilized localized high light (HL) stress and ROS treatments to trigger rapid systemic signaling.
• Employed quantitative PCR (qPCR) to analyze gene expression for local perception and distal signal reception.
• Investigated mutants including thylakoidal ascorbate peroxidase (tapx), singlet oxygen (1O2)-retrograde signaling (ex1/ex2), and apoplastic signaling (rbohD/F).

Main Results:

• Thylakoidal ascorbate peroxidase (tAPX) and EXECUTER 1 are crucial for perceiving both direct HL and systemic acclimation stress.
• Apoplastic RBOHs (respiratory burst oxidase homologs) are essential for the systemic spread of acclimation signals, but not for local perception.
• Localized singlet oxygen ((1)O2) induction strongly triggered systemic responses, with qPCR revealing a direct vascular connection component in SAA signaling.

Conclusions:

• An EXECUTER-dependent (1)O2 retrograde signal is vital for both local and long-distance acclimation signaling mediated by RBOH proteins.
• This (1)O2 signaling pathway is distinct from other high light (HL) signaling mechanisms.
• Direct vascular connections play a significant role in the spatial and temporal induction of systemic acquired acclimation (SAA).