To study both local (direct) and systemic (distant) responses to electromagnetic field stimulation in wild type and mutant plants with different inhibitors and to measure the accumulation of two transcripts (as markers for stress response) at several times after exposure (immediately after exposure and after 5, 15, 30, and 60 min.).
Naproxen (abscisic acid biosynthesis inhibitor) was added to the culture medium of hydroponically grown wild type tomatoes 24 h before electromagnetic field stimulation. Calcium counteracting drugs (EGTA and LaCl3) were sprayed simultaneously on the exposed leaf of wild type plants 30 min. before stimulation.
Exposure duration: continuous for 10 min
|Exposure duration||continuous for 10 min|
|electric field strength||5 V/m||-||-||-||-|
Exposing total wild type tomato evoked rapid accumulation of bZIP mRNA in the terminal leaf with kinetics very similar to that seen in response to wounding, while in the abscisic acid mutant (Sitiens) the response was more rapid, but transient.
Exposing just the oldest leaf of a wild type tomato evoked bZIP mRNA accumulation both locally in the exposed leaf and systemically in the unexposed (distant) leaf, although systemic accumulation was delayed somewhat.
Accumulation of Pin2 mRNA was less than bZIP in both the exposed and distant leaves in wild type, but there was no delay in the systemic response. In Sitiens, bZIP mRNA accumulation was far less than in wild type in both local and distant leaves, while Pin2 mRNA accumulation was stronger in the exposed leaf, but totally prevented in the systemic leaf.
In the jasmonic acid mutant (JL-5) and in wild type plants treated with naproxen, responses were similar to those in the abscisic acid mutant, while treatment of the exposed leaf with calcium antagonists totally abolished both local and systemic increases in bZIP transcript accumulation.
In conclusion, the data provide evidence that tomato plants are a good model to study the impact of radiofrequency electromagnetic fields as they perceive and respond to electromagnetic fields as though it was an injurious treatment (wound). The findings support the contention that there are two different signals evoking gene expression: a slower one evoking bZIP accumulation and a faster signal evoking Pin2 mRNA accumulation. Finally, they support a complex role for abscisic acid and jasmonic acid in the transcriptional responses.