Institutional Publications

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Author: search.filters.author.Mithöfer, AxelSubject: search.filters.subject.Arabidopsis thaliana

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    Calmodulin-like protein CML37 is a positive regulator of ABA during drought stress in Arabidopsis
    (Taylor & Francis Group, 2015) Scholz, Sandra S; Reichelt, Michael; Vadassery, Jyothilakshmi; Mithöfer, Axel
    Plants need to adapt to various stress factors originating from the environment. Signal transduction pathways connecting the recognition of environmental cues and the initiation of appropriate downstream responses in plants often involve intracellular Ca(2+) concentration changes. These changes must be deciphered into specific cellular signals. Calmodulin-like proteins, CMLs, act as Ca(2+) sensors in plants and are known to be involved in various stress reactions. Here, we show that in Arabidopsis 2 different CMLs, AtCML37 and AtCML42 are antagonistically involved in drought stress response. Whereas a CML37 knock-out line, cml37, was highly susceptible to drought stress, CML42 knockout line, cml42, showed no obvious effect compared to wild type (WT) plants. Accordingly, the analysis of the phytohormone abscisic acid (ABA) revealed a significant reduction of ABA upon drought stress in cml37 plants, while in cml42 plants an increase of ABA was detected. Summarizing, our results show that both CML37 and CML42 are involved in drought stress response but show antagonistic effects.
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    Systemic cytosolic Ca2+ elevation is activated upon wounding and herbivory in Arabidopsis
    (John Wiley & Sons, 2015) Kiep, Victoria; Vadassery, Jyothilakshmi; Lattke, Justus; Maaß, Jan-Peter; Boland, Wilhelm; Peiter, Edgar; Mithöfer, Axel
    Calcium ion (Ca2+) signalling triggered by insect herbivory is an intricate network with multiple components, involving positive and negative regulators. Real-time, noninvasive imaging of entire Arabidopsis thaliana rosettes was employed to monitor cytosolic free calcium ([Ca2+]cyt) elevations in local and systemic leaves in response to wounding and Spodoptera littoralis feeding. Luminescence emitted by the cytosol-localized Ca2+ reporter aequorin was imaged using a high-resolution photon-counting camera system. Spodoptera littoralis feeding on Arabidopsis induced both local and systemic [Ca2+]cyt elevations. Systemic [Ca2+]cyt signals were found predominantly in adjacent leaves with direct vascular connections to the treated leaf and appeared with a delay of 1 to 2 min. Simulated herbivory by wounding always induced a local [Ca2+]cyt response, but a systemic one only when the midrib was wounded. This systemic [Ca2+]cyt response was suppressed by the presence of insect-derived oral secretions as well as in a mutant of the vacuolar cation channel, Two Pore Channel 1 (TPC1). Our results provide evidence that in Arabidopsis insect herbivory induces both local and systemic [Ca2+]cyt signals that distribute within the vascular system. The systemic [Ca2+]cyt signal could play an important signalling role in systemic plant defence.