With or without a Ca 2+ signal? A proteomics approach towards Ca 2+ dependent and independent proteome changes in response to oxidative stress in A. thaliana
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Calcium (Ca 2+ ) and reactive oxygen species (ROS) are key secondary messengers in plant stress signaling, yet their interplay in regulating proteome-wide responses remains poorly understood. In this study, we employed label-free quantitative (LFQ) proteomics to investigate Ca 2+ -dependent and independent changes in the proteome of Arabidopsis thaliana leaves upon oxidative stress induced by hydrogen peroxide (H 2 O 2 ). To dissect the role of Ca 2+ signaling, we inhibited H 2 O 2 -induced Ca 2+ transients by pretreatment with LaCl 3 , a plasma membrane Ca 2+ channel blocker. We then analysed the proteome of plants treated with H 2 0 2 or ddH 2 O after 10 and 30 min of treatment and detected 3724 and 3757 proteins, respectively. From these, 581 proteins showed significant changes in abundance after 10 min and 909 proteins after 30 min. Remarkably, the combined LaCl 3 and H 2 O 2 treatment resulted in the highest number of differentially abundant proteins (DAPs), indicating a strong attenuating effect of Ca 2+ signaling on the oxidative stress response. Specifically responsive to only H 2 O 2 were 37 and 57 proteins with distinct subsets of strictly Ca 2+ -dependent, partially Ca 2+ - dependent, and Ca 2+ -independent proteins. Notably, Ca 2+ -independent H 2 O 2 -responsive proteins predominantly showed increased abundance, while strictly Ca 2+ -dependent proteins exhibited decreased abundance, suggesting a role for Ca 2+ signaling in protein degradation. Furthermore, three proteins—WLIM1, CYP97C1, and AGAP1—underwent Ca 2+ -dependent shifts between the two time points, pointing to a dynamic nature of Ca 2+ -regulated proteomic changes. This study provides novel insights into short-term Ca 2+ -dependent and independent regulation of the Arabidopsis leaf proteome in response to oxidative stress, identifying key stress-responsive proteins and potential new targets for further research on plant stress resilience mechanisms.
