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Authors: Chang Zhang, Zhenxiang Li, Tingting Sun, Shoujian Zang, Dongjiao Wang, Yachun Su, Qibin Wu and Youxiong Que.
Journal of Agricultural and Food Chemistry (2024)
Abstract: "Calcium (Ca2+) is a second messenger in various physiological processes within plants. The significance of the Ca2+/H+ exchanger (CAX) has been established in facilitating Ca2+ transport in plants; however, disease resistance functions of the CAX gene remain elusive. In this study, we conducted sequence characterization and expression analysis for a sugarcane CAX gene, ScCAX4 (GenBank Accession Number: MW206380). In order to further investigate the disease resistance functions, this gene was then transiently overexpressed in Nicotiana benthamiana leaves, which were subsequently inoculated with Fusarium solani var. coeruleum. Results showed that ScCAX4 overexpression increased the susceptibility of N. benthamiana to pathogen infection by regulating the expression of genes related to salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) pathways, suggesting its negative role in disease resistance. Furthermore, we genetically transformed the ScCAX4 gene into N. benthamiana and obtained three positive T2 generation lines. Interestingly, the symptomatology of transgenic plants was consistent with that of transient overexpression after pathogen inoculation. Notably, the JA content in transgenic overexpression lines was significantly higher than that in the wild-type. RNA-seq revealed that ScCAX4 could mediate multiple signaling pathways, and the JA signaling pathway played a key role in modulating disease resistance. Finally, a regulatory model was depicted for the increased susceptibility to pathogen infection conferred by the ScCAX4 gene. This study provides genetic resources for sugarcane molecular breeding and the research direction for plant CAX genes."
Authors: Zilu Zhang, Qi Wang, Haiqiao Yan, Xiaoyan Cang, Wei Li, Jinyu He, Meixiang Zhang, Laiqing Lou, Ran Wang and Ming Chang.
New Crops (2024)
Abstract: "Calcium ions (Ca2+) serve as key messengers in plant immune reactions. A typical Ca2+ signaling involves three steps: encoding specific Ca2+ signatures by Ca2+-permeable channels, decoding Ca2+ signals by Ca2+ sensors, and downstream responses. This review focuses on plasma membrane-localized Ca2+-permeable channels and cytosolic Ca2+ sensors, unraveling their roles in cytosolic Ca2+ influx and immune signaling during pattern-triggered immunity, effector-triggered immunity, and autoimmunity. Several unresolved questions were highlighted, including the regulation of Ca2+-permeable channel activity for immune induction and the mechanism behind Ca2+ influx-triggered hypersensitive response cell death. This concise overview provides insights into the complex interplay of Ca2+ signaling in plant immunity, paving the way for future investigations on molecular plant-microbe interactions."
Authors: Cheng Zhang, Charles Tetteh, Sheng Luo, Pinyuan Jin, Xingqian Hao, Min Sun, Nan Fang, Yingjun Liu and Huajian Zhang.
Molecular Plant Pathology (2024)
Abstract: Pectin has been extensively studied in animal immunity, and exogenous pectin as a food additive can provide protection against inflammatory bowel disease. However, the utility of pectin to improve immunity in plants is still unstudied. Here, we found exogenous application of pectin triggered stomatal closure in Arabidopsis in a dose- and time-dependent manner. Additionally, pectin activated peroxidase and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase to produce reactive oxygen species (ROS), which subsequently increased cytoplasmic Ca2+ concentration ([Ca2+]cyt) and was followed by nitric oxide (NO) production, leading to stomatal closure in an abscisic acid (ABA) and salicylic acid (SA) signalling-dependent mechanism. Furthermore, pectin enhanced the disease resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) with mitogen-activated protein kinases (MPKs) MPK3/6 activated and upregulated expression of defence-responsive genes in Arabidopsis. These results suggested that exogenous pectin-induced stomatal closure was associated with ROS and NO production regulated by ABA and SA signalling, contributing to defence against Pst DC3000 in Arabidopsis.
Authors: Vilde Olsson Lalun, Maike Breiden, Sergio Galindo-Trigo, Elwira Smakowska-Luzan, Rüdiger Simon and Melinka A. Butenko.
bioRxiv (2024)
Abstract: "The abscission of floral organs and emergence of lateral roots in Arabidopsis is regulated by the peptide ligand INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) and the receptor protein kinases HAESA (HAE) and HAESA-LIKE 2 (HSL2). During these cell separation processes, the plant induces defense-associated genes to protect against pathogen invasion. However, the molecular coordination between abscission and immunity has not been thoroughly explored. Here we show that IDA induces a release of cytosolic calcium ions (Ca2+) and apoplastic production of reactive oxygen species, which are signatures of early defense responses. In addition, we find that IDA promotes late defense responses by the transcriptional upregulation of genes known to be involved in immunity. When comparing the IDA induced early immune responses to known immune responses, such as those elicited by flagellin22 treatment, we observe both similarities and differences. We propose a molecular mechanism by which IDA promotes signatures of an immune response in cells destined for separation to guard them from pathogen attack."
Authors: Yuli Du, Heng Zhang, Kunpeng Jia, Zongyan Chu, Shican Xu, Lam-Son Phan Tran, Jinggong Guo, Weiqiang Li and Kun Li.
Physiologia Plantarum (2024)
Abstract: "In terrestrial plants, stomata in the leaf epidermis formed by guard cells are the major pathways for gas exchange. However, opened stomata also provide a major channel for pathogen entry. At the pre-invasive stage, plants actively close stomata to prevent pathogen attack, which is termed stomatal immunity, and plant hormones are involved in this process. Here, we summarize recent advances in the role of abscisic acid (ABA) in promoting stomatal immunity to prevent pathogen entry. Additionally, salicylic acid shares common downstream elements with ABA to promote stomatal immunity, whereas reactive oxygen species and Ca2+ act as critical signals to cross-talk with ABA signalling to regulate stomatal movement, and they also enhance the effect of ABA in stomatal immunity. On the other hand, at the post-invasive stage, closed stomata create a water-soaked environment that allows pathogen multiplication, and ABA signalling is hijacked by pathogens to reduce stomatal aperture. Here, we propose a model of dual roles of ABA-mediated stomatal closure during plant-pathogen interaction and offer emerging consequences and questions for ABA-mediated stomatal immunity."
Authors: Yuri Aratani, Takuya Uemura, Takuma Hagihara, Kenji Matsui and Masatsugu Toyota.
Nature Communications (2023)
Editor's view: Plants sense volatiles emitted by injured neighboring plants and elicit defense responses to external threats. Here, the authors show that Arabidopsis leaves uptake two green leaf volatiles via stomata and trigger cytosolic Ca2+ defense signaling.
Abstract: "Plants perceive volatile organic compounds (VOCs) released by mechanically- or herbivore-damaged neighboring plants and induce various defense responses. Such interplant communication protects plants from environmental threats. However, the spatiotemporal dynamics of VOC sensory transduction in plants remain largely unknown. Using a wide-field real-time imaging method, we visualize an increase in cytosolic Ca2+ concentration ([Ca2+]cyt) in Arabidopsis leaves following exposure to VOCs emitted by injured plants. We identify two green leaf volatiles (GLVs), (Z)-3-hexenal (Z-3-HAL) and (E)-2-hexenal (E-2-HAL), which increase [Ca2+]cyt in Arabidopsis. These volatiles trigger the expression of biotic and abiotic stress-responsive genes in a Ca2+-dependent manner. Tissue-specific high-resolution Ca2+ imaging and stomatal mutant analysis reveal that [Ca2+]cyt increases instantly in guard cells and subsequently in mesophyll cells upon Z-3-HAL exposure. These results suggest that GLVs in the atmosphere are rapidly taken up by the inner tissues via stomata, leading to [Ca2+]cyt increases and subsequent defense responses in Arabidopsis leaves."
Authors: Muhammad Saad Shoaib Khan, Sulaiman Ahmed, Aziz ul Ikram, Fakhir Hannan, Muhammad Umair Yasin, Jin Wang, Biying Zhao, Faisal Islam and Jian Chen.
Physiologia Plantarum (2023)
Highlights: • Melatonin acts as a redox network regulator in plants via regulating secondary messengers signaling. • Melatonin regulates the activity of redox-sensitive proteins and transcription factors. • Melatonin influences gene expression and physiological processes in response to stresses. • Melatonin synergically work with other hormones to confer plant resistance and stress adaptability.
Abstract: "Plants being sessile in nature, are exposed to unwarranted threats as a result of constantly changing environmental conditions. These adverse factors can have negative impacts on their growth, development, and yield. Hormones are key signaling molecules enabling cells to respond rapidly to different external and internal stimuli. In plants, melatonin (MT) plays a critical role in the integration of various environmental signals and activation of stress-response networks to develop defense mechanisms and plant resilience. Additionally, melatonin can tackle the stress-induced alteration of cellular redox equilibrium by regulating the expression of redox homeostasis-related genes and proteins. The purpose of this article is to compile and summarize the scientific research pertaining to MT's effects on plants' resilience to biotic and abiotic stresses. Here, we have summarized that MT exerts a synergistic effect with other phytohormones, for instance, ethylene, jasmonic acid, and salicylic acid, and activates plant defense-related genes against phytopathogens. Furthermore, MT interacts with secondary messengers like Ca2+, nitric oxide, and reactive oxygen species to regulate the redox network. This interaction triggers different transcription factors to alleviate stress-related responses in plants. Hence, the critical synergic role of MT with diverse plant hormones and secondary messengers demonstrates phytomelatonin's importance in influencing multiple mechanisms to contribute to plant resilience against harsh environmental factors."
Authors: Trupti Gaikwad, Susan Breen, Emily Breeze, Rana M. Fraz Hussain, Satish Kulasekaran, Marta de Torres-Zabala, David Horsell, Lorenzo Frigerio and Murray Grant.
bioRxiv (2023)
Abstract: "Successful recognition of pathogen effectors by plant disease resistance proteins (effector triggered immunity, ETI) contains the invading pathogen through a localized hypersensitive response (HR). In addition, ETI activates long-range signalling cascades that establish broad spectrum systemic acquired resistance (SAR). Using a novel and sensitive reporter we have been able to image the spatio- temporal dynamics of SAR. We demonstrate that local ETI triggered SAR signal generation, followed by rapid propagation and establishment in systemic responding leaves, is dependent on both jasmonate biosynthesis and perception. Further, ETI initiates calcium- and jasmonate-dependent systemic surface electrical potentials, reminiscent of those activated by herbivory but with slower propagation kinetics. Thus, jasmonate signalling is crucial to the initiation and establishment of systemic defence responses against a diverse range of phytopathogens."
Authors: Arkadipta Bakshi, Sarah J. Swanson and Simon Gilroy.
Cell Calcium (2023)
Highlights • Touch- and wound-induced leaf movements in Mimosa plants require Ca2+ signals • Ca2+ increases move sequentially through the pulvini, the motor organs of the leaf • Ca2+ increases in the pulvini are required to trigger leaf movements • Mimosa's leaf movements deter insect herbivores
Abstract: "Mimosa pudica, the sensitive plant, responds to stimuli such as touch and wounding with leaf movements that propagate throughout the plant. The motion is driven by changes in the turgor of specialized cells in a set of motor organs called pulvinae. By imaging cellular Ca2+ levels as the wave of movement propagates through the leaf, Hagihara and colleagues now show that Ca2+ signals precede and predict the pulvinar movements. These results provide compelling support for a model where Mimosa uses a Ca2+-related response system to trigger its leaf movements. These researchers then used CRISPR to delete a critical genetic regulator of pulvinar development, producing plants with immobile leaves. These plants experienced more herbivory than wild type, suggesting that the Ca2+-triggered leaf movements are an adaptation to deter herbivory."
Authors: Heike Seybold, Jennifer Bortlik, Xiyuan Jiang, Anja Liese, Benjamin Conrads, Wolfgang Hoehenwarter, Susanne Matschi and Tina Romeis.
bioRxiv (2022)
Abstract: "In nature plants are constantly challenged by simultaneous abiotic and biotic stresses, and under conflicting stress scenarios prioritization of stress responses is required for plant survival. Calcium-dependent protein kinase CPK5 is a central hub in local and distal immune signaling, required for hormone salicylic acid (SA)-dependent immunity and pathogen resistance. Here we show that CPK5-dependent immune responses and pathogen resistance are inhibited upon abscisic acid (ABA) treatment or in genetic mutant backgrounds lacking PP2C phosphatase activities including abi1-2, whereas immune responses are enhanced by co-expression of active ABI1 phosphatase variants. Biochemical studies and mass spectrometry-based phospho-site analysis reveal a direct ABI1 phosphatase-catalyzed de-phosphorylation of CPK5 auto-phosphorylation site T98. Mimicking continuous de-phosphorylation in CPK5T98A leads to enhanced ROS production and more resistant plants, mimicking the auto-phosphorylated status in CPK5T98D, reduces CPK5-mediated immune responses. Mechanistic insight identifies differential phosphorylation at T98 in the N-terminal domain of CPK5 to control the level of interaction between the kinase and its substrate protein rather than CPK5 catalytic activity. Thus, CPK5-catalyzed immune signaling may become discontinued even at an elevated cytoplasmic calcium concentration. Our work reveals an elegant mechanism for stress response prioritization in plants: The ABA-dependent phosphatase ABI1, negative regulator of abiotic responses, functions as positive regulator of biotic stress responses, stabilizing CPK5-dependent immune signaling in the absence of ABA. Continuous pathogen survey activates plant immunity in environmentally friendly conditions, whereas under severe abiotic stress the phosphatase/kinase pair prohibits immune signaling through a direct biochemical switch involving two key regulatory enzymes of these antagonistic pathways."
Authors: Chaoyi Hu, Shaofang Wu, Jiajia Li, Han Dong, Changan Zhu, Ting Sun, Zhangjian Hu, Christine H. Foyer and Jingquan Yu.
New Phytologist (2022)
Abstract: "• Herbivory severely affects plant growth, posing a threat to crop production. Calcium ion (Ca2+) signaling and accumulation of jasmonates (JAs) are activated in plant response to herbivore attack leading to the expression of defense pathways. However, little is known about how the Ca2+ signal modulates JA biosynthesis. • We used diverse techniques, including CRISPR/Cas9, UPLC-MS/MS, and molecular biology methods to explore the role of ETHYLENE RESPONSE FACTOR 16 in Ca2+ signals-triggered JA burst during herbivore defenses in tomato. • Here we show that simulated herbivory induces GLUTAMATE RECEPTOR LIKE3.3/ 3.5 (GLR3.3/3.5)-dependent increases in electrical activity, Ca2+ influx and increases the levels of CALMODULIN2 (CaM2) and ERF16 transcripts in tomato. The interaction between CaM2 and ERF16 promotes JA biosynthesis by enhancing the transcriptional activity of ERF16, which increases the activation of ERF16 expression, and causes expression of LIPOXYGENASE D (LOXD), AOC, and 12-OXO-PHYTODIENOIC ACID REDUCTASE 3 (OPR3), the key genes in JA biosynthesis. Mutation of CaM2 results in decreased JA accumulation, together with the expression of JA biosynthesis-related genes leading to reduced resistance to the cotton bollworm Helicoverpa armigera. • These findings reveal a molecular mechanism underpinning the Ca2+ signals-initiated systemic JA burst and emphasize the pivotal role of Ca2+ signals/ ERF16 crosstalk in herbivore defenses."
Authors: Mamoru Matsumura, Mika Nomoto, Tomotaka Itaya, Yuri Aratani, Mizuki Iwamoto, Takakazu Matsuura, Yuki Hayashi, Tsuyoshi Mori, Michael J. Skelly, Yoshiharu Y. Yamamoto, Toshinori Kinoshita, Izumi C. Mori, Takamasa Suzuki, Shigeyuki Betsuyaku, Steven H. Spoel, Masatsugu Toyota and Yasuomi Tada.
Nature Communications (2022)
Editor's view: Plant immunity can be induced by pathogen signals or environmental cues. Here, the authors show that plant leaves use trichomes to sense incoming raindrops and trigger basal defence responses to protect against subsequent microbial infection.
Abstract: "Perception of pathogen-derived ligands by corresponding host receptors is a pivotal strategy in eukaryotic innate immunity. In plants, this is complemented by circadian anticipation of infection timing, promoting basal resistance even in the absence of pathogen threat. Here, we report that trichomes, hair-like structures on the epidermis, directly sense external mechanical forces, including raindrops, to anticipate pathogen infections in Arabidopsis thaliana. Exposure of leaf surfaces to mechanical stimuli initiates the concentric propagation of intercellular calcium waves away from trichomes to induce defence-related genes. Propagating calcium waves enable effective immunity against pathogenic microbes through the CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR 3 (CAMTA3) and mitogen-activated protein kinases. We propose an early layer of plant immunity in which trichomes function as mechanosensory cells that detect potential risks."
Authors: Xin Liu, Sabir Hussain, Wen Xie, Zhaojiang Guo, Qingjun Wu, Shaoli Wang, Yong Liu and Youjun Zhang.
Entomologia Experimentalis et Applicata (2021)
Abstract: "The phytophagous whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) causes serious crop yield losses around the world especially by vectoring viruses. Exogenous jasmonic acid (JA) induces direct plant resistance to B. tabaci, but the underlying mechanism of JA-induced exogenous defenses is not well understood. Here, we demonstrate that exogenous JA not only increases the cytosolic Ca2+ concentration ([Ca2+]cyt) in tomato mesophyll cells but also induces the expression of Ca2+-sensor genes and plant defense genes. Pretreatment with Ca2+ inhibitor (ruthenium red) significantly repressed the elevation of [Ca2+]cyt, expression of JA-induced genes, and emission of plant volatiles induced by JA, thus reducing the JA-induced direct (feeding choice and fitness of B. tabaci) and indirect [olfactory choice and parasitism by the parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae)] plant resistance to B. tabaci. These results indicate that the Ca2+ signal induced by JA mediates and directs the plants defenses against whitefly. Present results will not only give us a better understanding of how exogenous JA influences the crop community, but also deliver some clues for the potential application of exogenous JA, as a plant elicitor, in whitefly management."
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Authors: Sara Hailemariam, Chao-Jan Liao and Tesfaye Mengiste.
Trends in Plant Science (2024)
Highlights: Receptor-like cytoplasmic kinases (RLCKs) have become major players in plant immunity regardless of the pathways involved. RLCKs form regulatory nodes that link receptors to downstream regulators that modulate plant hormones, Ca2+ signaling, reactive oxygen species (ROS) accumulation as well as activation of mitogen-activated protein kinases (MAPKs), transcription regulators, and immune gene expression. Phosphorylation, ubiquitination, and other post-translational modifications by effectors regulate RLCKs, enabling functional versatility and homeostasis. As major integrators of signals from receptors, RLCKs are potential targets for biotechnological applications. RLCKs play pivotal roles in plant immunity by contributing to both PTI and ETI. Due to their critical functions, these kinases are targets for manipulation by pathogen effectors to attenuate PTI. RLCKs also directly or indirectly recognize effectors and activate ETI. The function of RLCKs in crop plant immunity is emerging.
Abstract: "The receptor-like kinase (RLK) family of receptors and the associated receptor-like cytoplasmic kinases (RLCKs) have expanded in plants because of selective pressure from environmental stress and evolving pathogens. RLCKs link pathogen perception to activation of coping mechanisms. RLK–RLCK modules regulate hormone synthesis and responses, reactive oxygen species (ROS) production, Ca2+ signaling, activation of mitogen-activated protein kinase (MAPK), and immune gene expression, all of which contribute to immunity. Some RLCKs integrate responses from multiple receptors recognizing distinct ligands. RLKs/RLCKs and nucleotide-binding domain, leucine-rich repeats (NLRs) were found to synergize, demonstrating the intertwined genetic network in plant immunity. Studies in arabidopsis (Arabidopsis thaliana) have provided paradigms about RLCK functions, but a lack of understanding of crop RLCKs undermines their application. In this review, we summarize current understanding of the diverse functions of RLCKs, based on model systems and observations in crop species, and the emerging role of RLCKs in pathogen and abiotic stress response signaling."
Authors: Chao Wang, Ren-Jie Tang, Senhao Kou, Xiaoshu Xu, Yi Lu, Kenda Rauscher, Angela Voelker and Sheng Luan
Nature (2024)
One-sentence summary: A study of calcium homeostasis in the plant Arabidopsis reveals two signalling pathways it uses to balance the objectives of growth and immunity by regulating the level of Ca2+ in the cytosol.
Abstract: "Calcium (Ca2+) is an essential nutrient for plants and a cellular signal, but excessive levels can be toxic and inhibit growth1,2. To thrive in dynamic environments, plants must monitor and maintain cytosolic Ca2+ homeostasis by regulating numerous Ca2+ transporters3. Here we report two signalling pathways in Arabidopsis thaliana that converge on the activation of vacuolar Ca2+/H+ exchangers (CAXs) to scavenge excess cytosolic Ca2+ in plants. One mechanism, activated in response to an elevated external Ca2+ level, entails calcineurin B-like (CBL) Ca2+ sensors and CBL-interacting protein kinases (CIPKs), which activate CAXs by phosphorylating a serine (S) cluster in the auto-inhibitory domain. The second pathway, triggered by molecular patterns associated with microorganisms, engages the immune receptor complex FLS2–BAK1 and the associated cytoplasmic kinases BIK1 and PBL1, which phosphorylate the same S-cluster in CAXs to modulate Ca2+ signals in immunity. These Ca2+-dependent (CBL–CIPK) and Ca2+-independent (FLS2–BAK1–BIK1/PBL1) mechanisms combine to balance plant growth and immunity by regulating cytosolic Ca2+ homeostasis."
Authors: Yanliang Guo and Hao Li.
In Book. "Melatonin in Plants: Role in Plant Growth, Development, and Stress Response" (2024). Editors: Anket Sharma and Golam Jalal Ahammed.
Abstract: "Numerous studies have proven evidence that melatonin plays an important regulatory role in plant growth, development, and defense against various biotic and abiotic stresses. As well as melatonin, plant hormones and many second messengers, such as calcium (Ca2+), reactive oxygen species (ROS), nitric oxide (NO), and hydrogen sulfide (H2S), also play important roles in the regulation of various physiological processes in plants. In recent years, increasing studies have indicated that melatonin interacts with plant hormones and many second messengers to regulate multiple physiological processes. The role of melatonin in regulating seed germination involves abscisic acid (ABA), gibberellins (GA), Ca2+ signal, and H2O2; in regulating stomatal movement involves ABA, Ca2+, ROS, and H2S; in regulating rhizogenesis involves auxin, ROS, and NO; in regulating fruit ripening involves ethylene (ETH), ROS, and NO; in regulating plant senescence involves ABA, cytokinins (CKs), Ca2+, ROS, and NO; in regulating tolerance to abiotic stress involves CK, ABA, ETH, jasmonic acid (JA), and all secondary signals mentioned above; in regulating disease resistance involves ETH, JA, salicylic acid (SA), ROS, and NO. Plant hormones and the second messengers also interact with each other, forming complex regulatory networks, to regulate multiple physiological processes in plants."
Authors: Deepika Mittal, Janesh Kumar Gautam, Mahendra Varma, Amrutha Laie, Shruti Mishra, Smrutisanjita Behera and Jyothilakshmi Vadassery.
Plant, Cell & Environment (2024)
Abstract: "Jasmonic acid-isoleucine (JA-Ile) is a plant defence hormone whose cellular levels are elevated upon herbivory and regulate defence signalling. Despite their pivotal role, our understanding of the rapid cellular perception of bioactive JA-Ile is limited. This study identifies cell type-specific JA-Ile-induced Ca2+ signal and its role in self-amplification and plant elicitor peptide receptor (PEPR)-mediated signalling. Using the Ca2+ reporter, R-GECO1 in Arabidopsis, we have characterized a monophasic and sustained JA-Ile-dependent Ca2+ signature in leaf epidermal cells. The rapid Ca2+ signal is independent of positive feedback by the JA-Ile receptor, COI1 and the transporter, JAT1. Microarray analysis identified up-regulation of receptors, PEPR1 and PEPR2 upon JA-Ile treatment. The pepr1 pepr2 double mutant in R-GECO1 background exhibits impaired external JA-Ile induced Ca2+cyt elevation and impacts the canonical JA-Ile responsive genes. JA responsive transcription factor, MYC2 binds to the G-Box motif of PEPR1 and PEPR2 promoter and activates their expression upon JA-Ile treatment and in myc2 mutant, this is reduced. External JA-Ile amplifies AtPep-PEPR pathway by increasing the AtPep precursor, PROPEP expression. Our work shows a previously unknown non-canonical PEPR-JA-Ile-Ca2+-MYC2 signalling module through which plants sense JA-Ile rapidly to amplify both AtPep-PEPR and jasmonate signalling in undamaged cells."
In: phys.org
"Plants emit volatile organic compounds (VOCs) into the atmosphere upon mechanical damages or insect attacks. Undamaged neighboring plants sense the released VOCs as danger cues to activate defense responses against upcoming threats."
Authors: Shuhuan Zhang, Weihao Miao, Ye Liu, Jiafu Jiang, Sumei Chen, Fadi Chen and Zhiyong Guan.
BMC Genomics (2023)
Abstract: "Background - Black spot disease caused by the necrotrophic fungus Alternaria spp. is one of the most devastating diseases affecting Chrysanthemum morifolium. There is currently no effective way to prevent chrysanthemum black spot. Results - We revealed that pre-treatment of chrysanthemum leaves with the methyl jasmonate (MeJA) significantly reduces their susceptibility to Alternaria alternata. To understand how MeJA treatment induces resistance, we monitored the dynamics of metabolites and the transcriptome in leaves after MeJA treatment following A. alternata infection. JA signaling affected the resistance of plants to pathogens through cell wall modification, Ca2+ regulation, reactive oxygen species (ROS) regulation, mitogen‐activated protein kinase cascade and hormonal signaling processes, and the accumulation of anti-fungal and anti-oxidant metabolites. Furthermore, the expression of genes associated with these functions was verified by reverse transcription quantitative PCR and transgenic assays. Conclusion - Our findings indicate that MeJA pre-treatment could be a potential orchestrator of a broad-spectrum defense response that may help establish an ecologically friendly pest control strategy and offer a promising way of priming plants to induce defense responses against A. alternata."
Authors: Shuhuan Zhang, Weihao Miao, Ye Liu, Jiafu Jiang, Sumei Chen, Fadi Chen and Zhiyong Guan.
Research Square (2023)
Abstract: "Background - Black spot disease caused by the necrotrophic fungus Alternaria spp. is one of the most devastating diseases affecting Chrysanthemum morifolium. There is currently no effective way to prevent chrysanthemum black spot. Results - We revealed that pre-treatment of chrysanthemum leaves with the plant hormone jasmonate (JA) significantly reduces their susceptibility to Alternaria alternata. To understand how JA treatment induces resistance, we monitored the dynamics of metabolites and the transcriptome in leaves after JA treatment following A. alternata infection. JA signaling affected the resistance of plants to pathogens through cell wall modification, Ca2+ regulation, reactive oxygen species (ROS) regulation, mitogen-activated protein kinase cascade and hormonal signaling processes, and the accumulation of anti-fungal and anti-oxidant metabolites. Furthermore, the expression of genes associated with these functions was verified by reverse transcription quantitative PCR and transgenic assays. Conclusion - Our findings indicate that JA pre-treatment could be a potential orchestrator of a broad-spectrum defense response that may help establish an ecologically friendly pest control strategy and offer a promising way of priming plants to induce defense responses against A. alternata.
Authors: Alexander Förderer and Jijie Chai.
The EMBO Journal (2023)
Abstract: "Plants must make decisions to balance their growth versus defense against pathogens. Signaling of the plant peptide hormone phytosulfokine (PSK) has emerged as a critical stimulus for growth promotion. In this issue of The EMBO Journal, Ding et al (2022) show that PSK signaling promotes nitrogen assimilation via phosphorylation of glutamate synthase 2 (GS2). In the absence of PSK signaling, the plants growth is stunted, but its resistance to disease is reinforced."
Authors: Yuxiang Jiang and Pingtao Ding.
Trends in Plant Science (2023)
Highlights: Calcium signaling is key in plant immune signaling, transmitting external or internal danger signals to activate downstream players. The spatial and temporal patterning of different calcium signatures reflects the formation of original stimuli, which also determines specific outputs. Multiple protein families have been identified as calcium channels to mediate calcium influx in plant immunity, including these localized in plasma membrane and many intracellular organelles. Recent breakthroughs have revealed that some plant NLRs are assembled into calcium channels to activate downstream immune responses. The calcium signal induces changes in both the transcription of genes and changes in the post-translational modification of proteins related to plant immunity. Advances in imaging and manipulating the calcium signals shed light on the spatiotemporal control of plant immune response.
Abstract: "Calcium ions (Ca2+) are prominent intracellular messengers in all eukaryotic cells. Recent studies have emphasized the crucial roles of Ca2+ in plant immunity. Here, we review the latest progress on the spatiotemporal control of Ca2+ function in plant immunity. We discuss discoveries of how Ca2+ influx is triggered upon the activation of immune receptors, how Ca2+-permeable channels are activated, how Ca2+ signals are decoded inside plant cells, and how these signals are switched off. Despite recent advances, many open questions remain and we highlight the existing toolkit and the new technologies to address the outstanding questions of Ca2+ signaling in plant immunity."
Authors: Takuma Hagihara, Hiroaki Mano, Tomohiro Miura, Mitsuyasu Hasebe and Masatsugu Toyota.
Nature Communications (2022)
Editor's view: Mimosa pudica moves its leaves within seconds of being touched or wounded. Here the authors show that such movements are triggered by rapid changes in Ca2+ and action and variation potentials and provide evidence that rapid movements help protect the plant from insect attacks.
Abstract: "Animals possess specialized systems, e.g., neuromuscular systems, to sense the environment and then move their bodies quickly in response. Mimosa pudica, the sensitive plant, moves its leaves within seconds in response to external stimuli; e.g., touch or wounding. However, neither the plant-wide signaling network that triggers these rapid movements nor the physiological roles of the movements themselves have been determined. Here by simultaneous recording of cytosolic Ca2+ and electrical signals, we show that rapid changes in Ca2+ coupled with action and variation potentials trigger rapid movements in wounded M. pudica. Furthermore, pharmacological manipulation of cytosolic Ca2+ dynamics and CRISPR-Cas9 genome editing technology revealed that an immotile M. pudica is more vulnerable to attacks by herbivorous insects. Our findings provide evidence that rapid movements based on propagating Ca2+ and electrical signals protect this plant from insect attacks."
Authors: Carl Procko, Ivan Radin, Charlotte Hou, Ryan A. Richardson, Elizabeth S. Haswell and Joanne Chory.
PNAS (2022)
Abstract: "Some of the most spectacular examples of botanical carnivory—in which predator plants catch and digest animals presumably to supplement the nutrient-poor soils in which they grow—occur within the Droseraceae family. For example, sundews of the genus Drosera have evolved leaf movements and enzyme secretion to facilitate prey digestion. The molecular underpinnings of this behavior remain largely unknown; however, evidence suggests that prey-induced electrical impulses are correlated with movement and production of the defense hormone jasmonic acid (JA), which may alter gene expression. In noncarnivorous plants, JA is linked to electrical activity via changes in cytoplasmic Ca2+. Here, we find that dynamic Ca2+ changes also occur in sundew (Drosera spatulata) leaves responding to prey-associated mechanical and chemical stimuli. Furthermore, inhibition of these Ca2+ changes reduced expression of JA target genes and leaf movements following chemical feeding. Our results are consistent with the presence of a conserved Ca2+-dependent JA signaling pathway in the sundew feeding response and provide further credence to the defensive origin of plant carnivory."
Authors: Monika Heyer, Sandra S. Scholz, Michael Reichelt, Grit Kunert, Ralf Oelmüller and Axel Mithöfer
Plant Molecular Biology (2021)
Key message: Calmodulin-like-proteins (CML) belong to a family of calcium-sensing proteins that are unique for plants and involved in many different developmental and stress-related reactions. In defense against herbivory, some pathogens and drought, CML37 acts as a positive and CML42 as a negative regulator, respectively. We provide evidence that both CMLs act antagonistically in the regulation of induced defense responses. A double knock-out line, cml37 x cml42, thus shows wild-type phenotypes upon all kind of stresses we used.
Abstract: "A transient increase in the cytosolic calcium concentration is one of the first reactions that can be measured in plant cells upon abiotic as well as biotic stress treatments. These calcium signals are sensed by calcium binding proteins such as calmodulin-like proteins (CMLs), which transduce the sensed information into appropriate stress responses by interacting with downstream target proteins. In previous studies, CML37 has been shown to positively regulate the plants’ defense against both the insect herbivore Spodoptera littoralis and the response to drought stress. In contrast, CML42 is known to negatively regulate those two stress responses. Here, we provide evidence that these two CMLs act antagonistically in the regulation of induced responses directed against drought and herbivory stress as well as in the defense against the necrotrophic pathogen Alternaria brassicicola. Both CMLs shape the plant reactions by altering the phytohormone signaling. Consequently, the phytohormone-regulated production of defensive compounds like glucosinolates is also antagonistically mediated by both CMLs. The finding that CML37 and CML42 have antagonistic roles in diverse stress-related responses suggests that these calcium sensor proteins represent important tools for the plant to balance and fine-tune the signaling and downstream reactions upon environmental stress."
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