Plant Immune Memory in Systemic Tissue Does Not Involve Changes in Rapid Calcium Signaling

Area of Science:

• Plant immunity
• Calcium signaling
• Systemic acquired resistance (SAR)

Background:

• Cytoplasmic calcium rises are early events in plant defense.
• Systemic acquired resistance (SAR) involves priming for enhanced defense.
• It remains unclear if calcium signaling differs in primed plants.

Purpose of the Study:

• To investigate calcium responses in systemic leaves of primed Arabidopsis plants.
• To determine if prior pathogen exposure alters calcium signaling upon secondary challenge.
• To explore the role of CPK5 in systemic calcium signaling during priming.

Main Methods:

• Utilized a novel approach for systemic calcium imaging in Arabidopsis.
• Employed the R-GECO1-mTurquoise calcium indicator for fluorescence-based measurements.
• Compared calcium responses in wild-type, cpk5 mutant, and CPK5-overexpressing lines.

Main Results:

• CPK5-overexpressing plants showed reinforced oscillatory calcium signatures in local tissues.
• No significant changes in flg22-induced calcium responses were detected in systemic tissues of primed plants.
• This lack of altered systemic calcium signaling was consistent across all tested genotypes.

Conclusions:

• Plant immune memory in distal tissues does not involve altered rapid calcium signaling upstream of CPK5.
• Enhanced pathogen resistance in primed plants relies on downstream defense mechanisms.
• Rapid calcium transients are not the primary mechanism for systemic immune memory in plants.