Both action potentials and variation potentials induce proteinase inhibitor gene expression in tomato

Area of Science:

• Plant Biology
• Molecular Biology
• Plant Physiology

Background:

• Tomato plants (Lycopersicon esculentum) exhibit systemic accumulation of proteinase inhibitor 2 (pin2) mRNA following wounding.
• Previous research indicated that chemical signals mediate these systemic responses.
• The role of electrical and hydraulic signals in systemic wound responses remained largely unexplored.

Purpose of the Study:

• To investigate whether electrical or hydraulic signals can induce systemic pin2 gene expression in tomato plants.
• To compare the efficacy of hydraulically induced variation potentials (VP) and electrically induced action potentials (AP) in triggering pin2 expression.

Main Methods:

• Mild flame treatment to induce hydraulic signals and local electrical responses (VP).
• Electrical stimulation to induce systemic electrical signals (AP).
• Measurement of VP and AP kinetic parameters.
• Quantification of pin2 mRNA levels in response to these stimuli.

Main Results:

• Flame-wounded plants showed significant electrical responses and a rapid, several-fold increase in pin2 mRNA.
• Electrically stimulated plants that transmitted an AP exhibited similar rapid increases in pin2 mRNA.
• Plants with minimal or no electrical signal showed no change in pin2 mRNA levels.
• Both VP and AP signals preceded the accumulation of pin2 mRNA in the receiving leaf.

Conclusions:

• Hydraulically induced VPs and electrically induced APs are capable of evoking pin2 gene expression in tomato plants.
• These electrical and hydraulic signals act as systemic wound signals in addition to previously identified chemical signals.
• The findings elucidate novel signaling pathways involved in plant defense responses.