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Calcium decoders and their targets: The holy alliance that regulate cellular responses in stress signaling. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2023; 134:371-439. [PMID: 36858741 DOI: 10.1016/bs.apcsb.2022.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Calcium (Ca2+) signaling is versatile communication network in the cell. Stimuli perceived by cells are transposed through Ca2+-signature, and are decoded by plethora of Ca2+ sensors present in the cell. Calmodulin, calmodulin-like proteins, Ca2+-dependent protein kinases and calcineurin B-like proteins are major classes of proteins that decode the Ca2+ signature and serve in the propagation of signals to different parts of cells by targeting downstream proteins. These decoders and their targets work together to elicit responses against diverse stress stimuli. Over a period of time, significant attempts have been made to characterize as well as summarize elements of this signaling machinery. We begin with a structural overview and amalgamate the newly identified Ca2+ sensor protein in plants. Their ability to bind Ca2+, undergo conformational changes, and how it facilitates binding to a wide variety of targets is further embedded. Subsequently, we summarize the recent progress made on the functional characterization of Ca2+ sensing machinery and in particular their target proteins in stress signaling. We have focused on the physiological role of Ca2+, the Ca2+ sensing machinery, and the mode of regulation on their target proteins during plant stress adaptation. Additionally, we also discuss the role of these decoders and their mode of regulation on the target proteins during abiotic, hormone signaling and biotic stress responses in plants. Finally, here, we have enumerated the limitations and challenges in the Ca2+ signaling. This article will greatly enable in understanding the current picture of plant response and adaptation during diverse stimuli through the lens of Ca2+ signaling.
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Eichstädt B, Lederer S, Trempel F, Jiang X, Guerra T, Waadt R, Lee J, Liese A, Romeis T. Plant Immune Memory in Systemic Tissue Does Not Involve Changes in Rapid Calcium Signaling. FRONTIERS IN PLANT SCIENCE 2021; 12:798230. [PMID: 34970294 PMCID: PMC8712724 DOI: 10.3389/fpls.2021.798230] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 11/26/2021] [Indexed: 05/09/2023]
Abstract
Upon pathogen recognition, a transient rise in cytoplasmic calcium levels is one of the earliest events in plants and a prerequisite for defense initiation and signal propagation from a local site to systemic plant tissues. However, it is unclear if calcium signaling differs in the context of priming: Do plants exposed to a first pathogen stimulus and have consequently established systemic acquired resistance (SAR) display altered calcium responses to a second pathogen stimulus? Several calcium indicator systems including aequorin, YC3.6 or R-GECO1 have been used to document local calcium responses to the bacterial flg22 peptide but systemic calcium imaging within a single plant remains a technical challenge. Here, we report on an experimental approach to monitor flg22-induced calcium responses in systemic leaves of primed plants. The calcium-dependent protein kinase CPK5 is a key calcium sensor and regulator of the NADPH oxidase RBOHD and plays a role in the systemic calcium-ROS signal propagation. We therefore compared flg22-induced cytoplasmic calcium changes in Arabidopsis wild-type, cpk5 mutant and CPK5-overexpressing plants (exhibiting constitutive priming) by introgressing the calcium indicator R-GECO1-mTurquoise that allows internal normalization through mTurquoise fluorescence. Aequorin-based analyses were included for comparison. Based on the R-GECO1-mTurquoise data, CPK5-OE appears to reinforce an "oscillatory-like" Ca2+ signature in flg22-treated local tissues. However, no change was observed in the flg22-induced calcium response in the systemic tissues of plants that had been pre-challenged by a priming stimulus - neither in wild-type nor in cpk5 or CPK5-OE-lines. These data indicate that the mechanistic manifestation of a plant immune memory in distal plant parts required for enhanced pathogen resistance does not include changes in rapid calcium signaling upstream of CPK5 but rather relies on downstream defense responses.
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Affiliation(s)
| | - Sarah Lederer
- Department for Biochemistry of Plant Interactions, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany
| | - Fabian Trempel
- Department for Biochemistry of Plant Interactions, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany
| | - Xiyuan Jiang
- Department for Biochemistry of Plant Interactions, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany
| | - Tiziana Guerra
- Dahlem Centre of Plant Sciences, Freie Universität Berlin, Berlin, Germany
- Leibniz Institute of Vegetable and Ornamental Crops, Großbeeren, Germany
| | - Rainer Waadt
- Entwicklungsbiologie der Pflanzen, Centre for Organismal Studies, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Justin Lee
- Department for Biochemistry of Plant Interactions, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany
| | - Anja Liese
- Department for Biochemistry of Plant Interactions, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany
| | - Tina Romeis
- Dahlem Centre of Plant Sciences, Freie Universität Berlin, Berlin, Germany
- Department for Biochemistry of Plant Interactions, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany
- *Correspondence: Tina Romeis,
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