Aequorin-Based In Vivo Luminescence Imaging Detects Calcium Signalling in Response to Biotic and Abiotic Stresses in Tomato

Abstract

The tomato (Solanum lycopersicum L.), a widely cultivated and economically important vegetable crop, is subject to a number of biotic and abiotic stresses in nature. Several abiotic and biotic stresses have been demonstrated to elevate the concentration of cytosolic free Ca2+ ([Ca2+]i) in Arabidopsis due to the influx of calcium ions. In this study, recombinant aequorin was introduced into the tomato in order to investigate the change in [Ca2+]i when treated with exogenous Ca2+. This resulted in strong luminescence signals, which were mainly observed in the roots. Luminescence signals were also detected in the whole plant, including the leaves, when a surfactant (Silwet L-77) was added to coelenterazine. The concentration of [Ca2+]i increased with the dosage of NaCl/elf18. The luminescence signals also showed a lower increase in intensity with elf18 treatment compared to NaCl treatment. Furthermore, the [Ca2+]i responses to other abiotic or biotic stresses, such as H2O2 and Pep1, were also evaluated. It was found that this transgenic tomato expressing aequorin can effectively detect changes in [Ca2+]i levels. The transgenic tomato expressing aequorin represents an effective tool for detecting changes in [Ca2+]i and provides a solid basis for investigating the adaptation mechanisms of tomatoes to various abiotic and biotic stresses. Moreover, the aequorin-based system would be a highly valuable tool for studying the specificity and crosstalk of plant signalling networks under abiotic and biotic stresses in tomatoes.