Quantitative analysis of herbivore-induced cytosolic calcium by using a Cameleon (YC 3.6) calcium sensor in Arabidopsis thaliana

Ca²⁺ is a key player in plant cell responses to biotic and abiotic stress. Owing to the central role of cytosolic Ca²⁺ (Ca²⁺]_cyt) during early signaling and the need for precise determination of Ca²⁺]_cyt variations, we used a Cameleon YC 3.6 reporter protein expressed in Arabidopsis thaliana to quantify Ca²⁺]_cyt variations upon leaf mechanical damage (MD), herbivory by 3rd and 5th instar larvae of Spodoptera littoralis and S. littoralis oral secretions (OS) applied to MD. YC 3.6 allowed a clear distinction between MD and herbivory and discriminated between the two larvae instars. To our knowledge this is the first report of quantitative Ca²⁺]_cyt determination upon herbivory using a Cameleon calcium sensor.