The language of calcium signaling

TPCs: FROM PLANT TO HUMAN

In 2005, the Arabidopsis thaliana two-pore channel TPC1 channel was identified as a vacuolar Ca2+-release channel. In 2009, three independent groups published studies on mammalian TPCs as nicotinic acid adenine dinucleotide phosphate (NAADP)-activated endolysosomal Ca2+ release channels, results that were eventually challenged by two other groups, claiming mammalian TPCs to be phosphatidylinositol-3,5-bisphosphate [PI(3,5)P2]-activated Na+ channels. By now this dispute seems to have been largely reconciled. Lipophilic small molecule agonists of TPC2, mimicking either the NAADP or the PI(3,5)P2 mode of channel activation, revealed, together with structural evidence, that TPC2 can change its selectivity for Ca2+ versus Na+ in a ligand-dependent fashion (N- vs. P-type activation). Furthermore, the NAADP-binding proteins Jupiter microtubule-associated homolog 2 protein (JPT2) and Lsm12 were discovered, corroborating the hypothesis that NAADP activation of TPCs only works in the presence of these auxiliary NAADP-binding proteins. Pathophysiologically, loss or gain of function of TPCs has effects on autophagy, exocytosis, endocytosis, and intracellular trafficking, e.g., LDL cholesterol trafficking leading to fatty liver disease or viral and bacterial toxin trafficking, corroborating the roles of TPCs in infectious diseases such as Ebola or COVID-19. Defects in the trafficking of epidermal growth factor receptor and β1-integrin suggested roles in cancer. In neurodegenerative lysosomal storage disease models, P-type activation of TPC2 was found to have beneficial effects on both in vitro and in vivo hallmarks of Niemann-Pick disease type C1, Batten disease, and mucolipidosis type IV. Here, we cover the latest on the structure, function, physiology, and pathophysiology of these channels with a focus initially on plants followed by mammalian TPCs, and we discuss their potential as drug targets, including currently available pharmacology.

BrCNGC12 and BrCNGC16 mediate Ca2+ absorption and transport to enhance resistance to tipburn in Chinese cabbage

Tipburn is a common physiological disorder in leafy vegetables, significantly impairing crop growth and commercial value. It is widely recognized that Ca2+ deficiency is a key factor triggering tipburn; however, the functions and regulatory mechanisms of genes conferring resistance remain largely unexplored. Through transcriptomic analysis of Chinese cabbage under normal (medium calcium, MCa) and Ca2+-deficient (low calcium, LCa) conditions, we observed that genes in the hormone and calcium signalling pathways exhibited significant responses to LCa stress. Among these, the cyclic nucleotide-gated ion channel (CNGC) genes BrCNGC12 and BrCNGC16, part of the calcium signalling pathway, were notably up-regulated and down-regulated, respectively, under LCa stress. Silencing BrCNGC12 in Chinese cabbage improves Ca2+ absorption and distribution, which strengthens tipburn resistance. Conversely, under LCa stress, heterologous expression of BrCNGC16 in Arabidopsis thaliana increases resistance to tipburn, whereas partial silencing of BrCNGC16 in Chinese cabbage diminishes resistance, with both outcomes linked to altered Ca2+ uptake and translocation. Additionally, overexpression of BrCNGC16 in Chinese cabbage promotes Ca2+ uptake and translocation, thereby enhancing resistance to tipburn and mitigating oxidative damage induced by Ca2+ deficiency. In conclusion, BrCNGC12 and BrCNGC16 play pivotal roles in tipburn resistance in Chinese cabbage, offering novel insights into the interplay between the calcium signalling pathway and tipburn resistance.

A conserved fungal effector disturbs Ca2+ sensing and ROS homeostasis to induce plant cell death

Acting as a major Ca2+ sensor, calmodulin (CaM) activates target proteins to regulate a variety of cellular processes. Here, we report that CaM-target binding is disturbed by a fungal virulence effector PdCDIE1 (Penicillium digitatum Cell Death-Inducing Effector 1), which results into reactive oxygen species (ROS)-dependent plant cell death. PdCDIE1 is an evolutionarily conserved fungal effector that exhibits plant cell death-inducing activity and contributes significantly to pathogen virulence. PdCDIE1 interacts with a plant heat shock protein Hsp70 that is antagonistic to ROS-dependent plant cell death. Hsp70 is a bona fide target of CaM and its CaM-binding domain also interacts with N-terminal PdCDIE1. The interaction between CaM and Hsp70 in citrus fruit is disturbed during pathogen infection but recovered during ΔPdCDIE1 mutant infection. Application of a CaM inhibitor and silencing of CaM genes induce plant cell death and high levels of ROS as PdCDIE1 does. These results reveal a molecular framework of effector-triggered susceptibility which integrates Ca2+ sensing and ROS homeostasis to induce plant cell death.

Systematic characterization of the calmodulin-like (CML) gene family in alfalfa and functional analysis of MsCML70 under salt stress

Calmodulin-like proteins (CMLs), which are widely involved in various abiotic stress responses, are important calcium ion sensors in plants. However, systematic identification and functional analysis of these proteins have not been performed in alfalfa. Here, a total of 211 MsCMLs were identified in the alfalfa genome. Conserved domain analysis revealed that most MsCMLs contained three EF-hand domains. A total of 17 tandem duplication events and 292 segmental duplication events were identified, indicating that segmental duplications were the major factor in the expansion of MsCMLs. There were 28, 36 and 18 MsCMLs that responded to drought, salt and cold stress, respectively, in alfalfa. In addition, MsCML70 overexpression significantly increased salt tolerance in Arabidopsis. MsCML70 participates in the plant salt stress response through various biological pathways, including transcriptional regulation, protein modification, plant hormone metabolism and secondary metabolism. Moreover, MsCML70 significantly increased the expression of HKT1 (high-affinity K+transporter 1), DREB19 (dehydration responsive element binding protein 19), PRX32 (peroxidase 32), JAL10 (jacalin-associated lectins 10), HB17 (homeobox 17), and NPF2.3 (nitrate transporter 2.3) under salt stress to promote tolerance to salt stress in Arabidopsis. The results of this study help elucidate the function of alfalfa CML genes and provide a new gene resource for the breeding of stress-resistant alfalfa.

Revealing non-trivial information structures in aneural biological tissues via functional connectivity

A central challenge in the progression of a variety of open questions in biology, such as morphogenesis, wound healing, and development, is learning from empirical data how information is integrated to support tissue-level function and behavior. Information-theoretic approaches provide a quantitative framework for extracting patterns from data, but so far have been predominantly applied to neuronal systems at the tissue-level. Here, we demonstrate how time series of Ca2+ dynamics can be used to identify the structure and information dynamics of other biological tissues. To this end, we expressed the calcium reporter GCaMP6s in an organoid system of explanted amphibian epidermis derived from the African clawed frog Xenopus laevis, and imaged calcium activity pre- and post- a puncture injury, for six replicate organoids. We constructed functional connectivity networks by computing mutual information between cells from time series derived using medical imaging techniques to track intracellular Ca2+. We analyzed network properties including degree distribution, spatial embedding, and modular structure. We find organoid networks exhibit potential evidence for more connectivity than null models, with our models displaying high degree hubs and mesoscale community structure with spatial clustering. Utilizing functional connectivity networks, our model suggests the tissue retains non-random features after injury, displays long range correlations and structure, and non-trivial clustering that is not necessarily spatially dependent. In the context of this reconstruction method our results suggest increased integration after injury, possible cellular coordination in response to injury, and some type of generative structure of the anatomy. While we study Ca2+ in Xenopus epidermal cells, our computational approach and analyses highlight how methods developed to analyze functional connectivity in neuronal tissues can be generalized to any tissue and fluorescent signal type. We discuss expanded methods of analyses to improve models of non-neuronal information processing highlighting the potential of our framework to provide a bridge between neuroscience and more basal modes of information processing.

Metal ions and nanomaterials for targeted bone cancer immunotherapy

Bone cancer remains a significant challenge in oncology, with limited success in current therapeutic approaches, particularly immunotherapy. Emerging research highlights the potential of integrating metal ions and nanomaterials for targeted immunotherapy in bone cancer. Metal ions, including calcium, magnesium, and zinc, play a significant role in modulating immune responses within the tumor microenvironment, affecting essential pathways necessary for immune activation. Meanwhile, nanomaterials, particularly metallic nanoparticles, offer precise drug delivery and immune system modulation, improving the efficacy of immunotherapeutic agents. This review explores the synergistic effects of metal ion-nanomaterial conjugates, discussing their role in enhancing immune cell activation, particularly T-cells and macrophages, and their potential for controlled drug release. We highlight preclinical advancements in bone cancer treatment using metal ion-responsive nanoparticles, and address current challenges such as biocompatibility and toxicity. Finally, we discuss the future prospects of these technologies in personalized and precision medicine, aiming to revolutionize bone cancer immunotherapy.

Genome-wide identification of SlIQMs and the regulatory effect of calcium on tomato seedlings under drought stress and phytohormone treatment

KEY MESSAGE

SlIQMs were identified, exogenous calcium and phytohormones induced their expression. SlIQMs's function were verified by VIGS. Calcium synergistically promoted seedling growth with ABA, IAA, MeJA and antagonized growth inhibition with GA3 or SA. The IQM genes, are crucial members of the calmodulin-binding protein family, play pivotal roles in plant growth and stress response. However, the existence and impact of IQM in tomato remain unclear. This study demonstrates that the SlIQMs are randomly distributed across the 4 chromosomes of tomato and exclusively located within the nucleus. Phylogenetic analysis classifies the SlIQMs into 3 distinct subclasses. Analysis of cis-acting elements reveals that SlIQMs may function in stress or hormone process. Quantitative reverse-transcriptase PCR analysis further testified that polyethylene glycol (PEG), abscisic acid (ABA), indole acetic acid (IAA), gibberellin (GA3), methyl jasmonate (MeJA), and salicylic acid (SA) induce expression levels of SlIQM1/2/3/5/6/7. Furthermore, exogenous calcium significantly alleviates detrimental effects on seedlings growth leaded by drought stress. Moreover, the relationships between hormones and calcium were explored. The results showed that calcium synergistically promoted the seedlings growth with ABA, IAA and MeJA, however antagonistic effects on inhibiting growth are observed between calcium and GA3 or SA. The virus-induced silencing of 6 candidate genes caused growth inhibition of tomato seedlings under drought stress and phytohormone treatment. These findings lay the foundation for a comprehensive study of the structure and biological function of SlIQM genes and the interaction between calcium and different plant hormones on plant growth.

Quinoline- and Pyrimidine-based Allosteric Modulators of the Sarco/Endoplasmic Reticulum Calcium ATPase

Small-molecule allosteric activators of the enzyme sarco/endoplasmic reticulum calcium ATPase (SERCA) hold promise as novel experimental tools to manipulate intracellular calcium concentrations and as therapeutic agents to treat medical conditions associated with elevated cytosolic calcium levels. Here, we synthesized and characterized 20 analogs of the known allosteric SERCA activator CDN1163 and tested their ability to stimulate SERCA activity. The structures of the compounds varied in the alkyl group of the parent scaffold's ether moiety as well as in the composition of the nitrogenous aromatic ring system. The most active compounds exhibited potencies in the sub-micromolar range while increasing enzyme activity by more than 25 %. The observed structure-activity relationships indicated that bulky alkyl groups in the ether moiety along with a quinoline ring methyl substituent were beneficial for activity. Replacement of the quinoline by a pyrimidine ring system reduced activity. To conceive a potential mechanism of action, we generated a molecular model of the transition state of SERCA when undergoing the rate-limiting step of its catalytic cycle. Subsequent blind docking with CDN1163 identified a high-affinity binding site close to the enzyme's ATP binding pocket, suggesting that the activators may accelerate SERCA's catalytic cycle by aiding in ATP binding and positioning.

Cryo-EM structures of Arabidopsis CNGC1 and CNGC5 reveal molecular mechanisms underlying gating and calcium selectivity

Plant cyclic nucleotide-gated channels (CNGCs) belong to the cyclic nucleotide-binding domain (CNBD) channel family, but are phylogenetically classified in a distinct branch. In contrast to their animal counterparts of K+-selective or non-selective cation channels, plant CNGCs mainly mediate Ca2+ influx and are involved in various physiological processes, such as stomatal movements, pollen-tube growth and immune responses. Here, we present the cryo-EM structure and electrophysiological analysis of plant CNGC representatives, Arabidopsis CNGC1 and CNGC5. We found that CNGC1 and CNGC5 contain a unique extracellular domain featuring disulfide bonds that is essential for channel gating via coupling of the voltage-sensing domain with the pore domain. The pore domain selectivity filter possesses a Gln residue at the constriction site that determines the Ca2+ selectivity. Replacement of this Gln with Glu, typically observed in CNBD-type non-selective cation channels, could convert CNGC1 and CNGC5 from Ca2+-selective channels to non-selective cation channels permeable to Ca2+, Na+ or K+. In addition, we found that the CNGC1 and CNGC5 CNBD homology domain contains intrinsic-ligand-like interactions, which may devoid the binding of cyclic nucleotides and lead to gating independent of cAMP or cGMP. This research not only provides a mechanistic understanding of plant CNGCs' function, but also adds to the comprehensive knowledge of the CNBD channels.

Plant intelligence dux: a comprehensive rebuttal of Kingsland and Taiz

Intelligence is a fundamental property for all life enabling an increased probability of survival and reproduction under wild circumstances. Kingsland and Taiz (2024) think that plants are not intelligent but seem unaware of the extensive literature about intelligence, memory, learning and chromatin topology in plants. Their views are consequently rejected. Their claim of fake quotations is shown to result from faulty reasoning and lack of understanding of practical biology. Their use of social media as scholarly evidence is unacceptable. Darwin's views on intelligence are described, and their pertinence to the adaptive responses of plants is discussed. Justifications for comments I have made concerning McClintock and her "thoughtful" cell, von Sachs writings as indicating purpose (teleonomy) to plant behaviour, Went and Thimann's allusions to plant intelligence and Bose legacy as the father of plant electrophysiology are described. These scientists were usually first in their field of knowledge, and their understanding was consequently deeper. The article finishes with a brief critical analysis of the 36 scientists who were used to condemn plant neurobiology as of no use. It is concluded that participants signed up to a false prospectus because contrary evidence was omitted.

Function of key ion channels in abiotic stresses and stomatal dynamics

Climate changes disrupt environmental and soil conditions that affect ionic balance in plants, presenting significant challenges to their survival and productivity. Membrane transporters are crucial for maintaining ionic homeostasis and regulating the movement of substances across plasma and organellar membranes, particularly under abiotic stresses. Among these abiotic stress-responsive mechanisms, stomata are critical for regulating water loss and carbon dioxide uptake, reflecting a plant's ability to respond and adapt to abiotic stresses effectively. This review highlights the role of ion transporters, including both anion and cation transporters in plant abiotic stress responses. It explores the interplay between different ion channels and regulatory components that enable plants to withstand key abiotic stresses such as drought, salinity, and heat. Moreover, we emphasized the contributions of three essential types of ion channels - potassium, anion, and calcium to abiotic stress-related stomatal regulation. These ion channels orchestrate complex signaling networks that allow plants to modulate stomatal behavior and maintain physiological balance under adverse conditions. This article provides valuable molecular and physiological insights into the mechanisms of ion transport and regulation for plants to adapt to environmental challenges. Thus, this review offers a useful foundation for developing innovative strategies to enhance crop resilience and performance in an era of increasingly unpredictable and harsh climates.

Molecular mapping and transfer of sheath blight resistance QTLs from PAU-shb8 to cultivated rice PR-121

Sheath blight, caused by Rhizoctonia solani, severely affects rice, causing 20-69% yield losses in tropical and temperate regions. Key challenges include the pathogen's broad host range, persistent sclerotia, climate change, and the reliance on semi-dwarf varieties. The disease's complex inheritance and lack of highly resistant cultivars hinder management, making resistant variety breeding a sustainable solution. This study mapped sheath blight resistance Quantitative trait locus (QTLs) from PAU-shb8, a moderately resistant rice line. This line exhibited moderate resistance with a disease score of 3 (RLH < 20%), whereas susceptible rice cultivar PR121 scored 9 (RLH > 60%). Screening of 1160 plants from BC1F5 and BC1F6 populations revealed 50.34% as moderately resistant, 37.76% moderately susceptible, and 11.88% susceptible. (QTL) mapping using 4622 SNP markers identified 20 QTLs across eight traits, with significant loci on chromosomes 2, 4, 6, 8, 9, 10, 11, and 12. Chromosome 12 harbored a cluster of QTLs associated with multiple traits, including RLH, lesion height, and disease score, while chromosome 8 exhibited a major QTL for RLH with a LOD score of 9.8 and 9.2% phenotypic variance. Genomic analysis pinpointed candidate genes related to resistance, such as leucine-rich repeat proteins and calcium/calmodulin-dependent protein kinases. Promising genotypes 7168, 7183, and 7152 demonstrated moderate resistance, combining key QTLs for RLH, disease severity, and lesion height with favorable agronomic traits. These backcross inbred lines are pivotal for breeding sheath blight-resistant rice varieties and for the expansion of resistance gene pool of sheath blight.

Cyclic nucleotide-gated ion channel 20 regulates melatonin-induced calcium signaling and cold tolerance in watermelon

Melatonin plays a crucial role in regulating plant cold tolerance, but the mechanisms underlying signal transduction remain elusive. In this study, we discovered that overexpression of the melatonin biosynthetic gene caffeic acid O-methyltransferase1 (COMT1) enhanced watermelon (Citrullus lanatus) cold tolerance, accompanied by the accumulation of cytosolic free calcium ([Ca2+]cyt), a stimulation of Ca2+ influx, and upregulation of 4 Ca2+-permeable channel genes (CNGC2/10/17/20). Conversely, the knockout of COMT1 exhibited contrasting effects compared with its overexpression. Knocking out the 4 CNGC genes revealed that only cyclic nucleotide-gated ion channel 20 (CNGC20) mediates melatonin-induced Ca2+ influx in response to cold stimuli. CNGC20 deletion impeded watermelon callus redifferentiation, prompting us to employ a virus-induced gene silencing strategy to suppress its expression. Silencing CNGC20 compromised COMT1 overexpression-induced [Ca2+]cyt accumulation, Ca2+ influx, and watermelon cold tolerance. Yeast 2-hybrid, bimolecular fluorescence complementation, firefly luciferase complementation imaging, and pull-down assays revealed an interaction between CNGC20 and calmodulin7 (CaM7). Overexpressing CaM7 inhibited melatonin-induced [Ca2+]cyt accumulation, Ca2+ influx, and watermelon cold tolerance. Conversely, silencing CaM7 increased [Ca2+]cyt accumulation, Ca2+ influx, and cold tolerance, whereas COMT1 overexpression failed to further enhance these responses in CaM7-silenced plants, indicating the negative regulation role of CaM7 in melatonin-mediated cold responses. Overall, these findings provide insights into the molecular mechanisms underlying melatonin-enhanced plant cold tolerance via Ca2+ signaling, holding potential for breeding/engineering cold-tolerant cucurbit varieties.

The concerted function of a novel class of transcription factors, ZBFs, in light, jasmonate, and abscisic acid signaling pathways

Several classes of transcription factors have been investigated in light signaling pathways that bind to the light-responsive elements (LREs) present in the promoters of light regulatory genes for transcriptional regulation. Some of these transcription factors have been shown to bind to numerous promoters through genome-wide ChIP-on-chip (ChIP-chip) studies. Furthermore, through the integration of ChIP-seq and RNA-seq techniques, it has been demonstrated that a transcription factor modifies the expression of numerous genes with which it interacts. However, the mode of action of these transcription factors and their dependency on other regulators in the pathway has just started to be unraveled. In this review, we focus on a particular class of transcription factors, ZBFs (Z-box-binding factors), and their associated partners within the same or other classes of transcription factors and regulatory proteins during photomorphogenesis. Moreover, we have further made an attempt to summarize the crosstalk of these transcription factors with jasmonic acid-, abscisic acid-, and salicylic acid-mediated defense signaling pathways. This review offers an in-depth insight into the manner in which ZBFs and their interactors reshape cellular functions and plant behavior. The underlying principles not only contribute to a comprehensive understanding but also establish a framework for analyzing the interplay between early developmental events and hormone signaling, a regulation orchestrated by the ZBF family.

Single-cell transcriptomic profiling of maize cell heterogeneity and systemic immune responses against Puccinia polysora Underw

Southern corn rust (SCR), caused by Puccinia polysora Underw (P. polysora), is a catastrophic disease affecting maize, leading to significant global yield losses. The disease manifests primarily as pustules on the upper surface of corn leaves, obscuring our understanding of its cellular heterogeneity, the maize's response to its infection and the underlying gene expression regulatory mechanisms. In this study, we dissected the heterogeneity of maize's response to P. polysora infection using single-cell RNA sequencing. We delineated cell-type-specific gene expression alterations in six leaf cell types, creating the inaugural single-cell atlas of a maize leaf under fungal assault. Crucially, by reconstructing cellular trajectories in susceptible line N110 and resistant line R99 during infection, we identified diverse regulatory programs that fortify R99's resistance across different leaf cell types. This research uncovers an immune-like state in R99 leaves, characterized by the expression of various fungi-induced genes in the absence of fungal infection, particularly in guard and epidermal cells. Our findings also highlight the role of the fungi-induced glycoside hydrolase family 18 chitinase 7 protein (ZmChit7) in conferring resistance to P. polysora. Collectively, our results shed light on the mechanisms of maize resistance to fungal pathogens through comparative single-cell transcriptomics, offering a valuable resource for pinpointing novel genes that bolster resistance to P. polysora.

Function of WAKs in Regulating Cell Wall Development and Responses to Abiotic Stress

Receptor-like kinases (RLKs) are instrumental in regulating plant cell surface sensing and vascular tissue differentiation. Wall-associated kinases (WAKs) are a unique group of RLKs that have been identified as key cell wall integrity (CWI) sensors. WAK signaling is suggested to be activated during growth in response to cell expansion or when the cell wall is damaged, for example, during pathogen attack. WAKs are proposed to interact with pectins or pectin fragments that are enriched in primary walls. Secondary walls have low levels of pectins, yet recent studies have shown important functions of WAKs during secondary wall development. Several wak mutants show defects in secondary wall thickening of the xylem vessels and fibers or the development of vascular bundles. This review will discuss the recent advances in our understanding of WAK functions during plant development and responses to abiotic stresses and the regulation of vascular tissue secondary wall development.

Rice Responses to Abiotic Stress: Key Proteins and Molecular Mechanisms

The intensification of global climate change and industrialization has exacerbated abiotic stresses on crops, particularly rice, posing significant threats to food security and human health. The mechanisms by which rice responds to these stresses are complex and interrelated. This review aims to provide a comprehensive understanding of the molecular mechanisms underlying rice's response to various abiotic stresses, including drought, salinity, extreme temperatures, and heavy metal pollution. We emphasize the molecular mechanisms and structural roles of key proteins involved in these stress responses, such as the roles of SLAC1 and QUAC1 in stomatal regulation, HKT and SOS proteins in salinity stress, heat shock proteins (HSPs) and heat stress transcription factors (HSFs) in temperature stress, and Nramp and ZIP transport proteins in response to heavy metal stress. This review elucidates the complex response networks of rice to various abiotic stresses, highlighting the key proteins and their related molecular mechanisms, which may further help to improve the strategies of molecular breeding.

Discovery, Characterization, and Anti-XOD Activity of Calcium Metallophore from Coix lacryma-jobi

In this work, coixalkyne A (1), a natural polynuclear calcium complex with a novel cross-shaped molecular architecture, was isolated from Coix lacryma-jobi L. along with the undescribed analogue coixalkyne B (2). Their structures were identified by means of NMR spectroscopy, ECD calculations, and single-crystal X-ray diffraction. It is noteworthy that the calcium ligands of 1 as well as compound 2 possess rare terminal alkynes and a nor-carbon sesquiterpene (C14) framework. The antihyperuricemic activity of C. lacryma-jobi and xanthine oxidase (XOD) inhibitory effects of 1-2 were elucidated by in vivo and in vitro assays, while the possible mechanism of action was suggested by molecular docking. Different from the reported chemical synthesis and protein calcium carriers, the discovery of compounds 1 and 2 provided new proof for the natural calcium metallophore in plants with xanthine oxidase inhibitory activity.

Genome-wide identification of CAMTA gene family in teak (Tectona grandis) and functional characterization of TgCAMTA1 and TgCAMTA3 in cold tolerance

BACKGROUND

Calmodulin-binding transcription activator (CAMTA) proteins play significant roles in signal transduction, growth and development, as well as abiotic stress responses, in plants. Understanding their involvement in the low-temperature stress response of teak is vital for revealing cold resistance mechanisms.

RESULTS

Through bioinformatics analysis, the CAMTA gene family in teak was examined, and six CAMTA genes were identified in teak. The encoded proteins were predicted to be located in the nucleus and exhibited hydrophilic properties, with molecular weights ranging from 103.4 to 123.3 kDa and isoelectric points ranging from 5.49 to 7.55. On the basis of protein sequence homology, the CAMTA family could be divided into three subgroups. Domain and 3D structure analyses demonstrated that all the TgCAMTA proteins contained the typical CAMTA domain with the CaMBD binding domain, which was exposed on the surface. Expression analysis of different tissues revealed the expression of TgCAMTA genes in teak roots, stems, leaves, flowers, fruits, and branches. Furthermore, the promoter region contained various cis-acting elements related to light, hormone, and abiotic stress responses. After low-temperature stress treatment, different expression patterns of TgCAMTAs were observed in teak roots, stems, and leaves, with TgCAMTA1 showing the highest expression level in leaves compared with stems. Transgenic lines carrying the TgCAMTA1/3 promoter::GUS construct cold stress induction of TgCAMTA1/3 genes revealed the presence of multiple low-temperature responsive cis-acting elements in the TgCAMTA1/3 promoter region. Subcellular localization analysis indicated that these genes were functional predominantly in the nucleus. Compared with wild-type Arabidopsis, TgCAMTA1/3-overexpressing Arabidopsis presented increased tolerance to freezing stress, with increased expression of AtCOR genes. Moreover, under low-temperature conditions, TgCAMTA3-overexpressing Arabidopsis presented significantly elevated expression levels of genes related to the CBF signaling pathway, including AtCBF1/2/3.

CONCLUSIONS

Our findings add significantly to the existing knowledge regarding cold stress tolerance and help elucidate cold response mechanisms in teak.

Calcium Signalling in Neurological Disorders, with Insights from Miniature Fluorescence Microscopy

Neurological disorders (NDs), such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and schizophrenia, represent a complex and multifaceted health challenge that affects millions of people around the world. Growing evidence suggests that disrupted neuronal calcium signalling contributes to the pathophysiology of NDs. Additionally, calcium functions as a ubiquitous second messenger involved in diverse cellular processes, from synaptic activity to intercellular communication, making it a potential therapeutic target. Recently, the development of the miniature fluorescence microscope (miniscope) enabled simultaneous recording of the spatiotemporal calcium activity from large neuronal ensembles in unrestrained animals, providing a novel method for studying NDs. In this review, we discuss the abnormalities observed in calcium signalling and its potential as a therapeutic target for NDs. Additionally, we highlight recent studies that utilise miniscope technology to investigate the alterations in calcium dynamics associated with NDs.

A regulatory network involving calmodulin controls phytosulfokine peptide processing during drought-induced flower abscission

Drought stress substantially decreases crop yields by causing flowers and fruits to detach prematurely. However, the molecular mechanisms modulating organ abscission under drought stress remain unclear. Here, we show that expression of CALMODULIN2 (CaM2) is specifically and sharply increased in the pedicel abscission zone in response to drought and plays a positive role in drought-induced flower drop in tomato (Solanum lycopersicum). Due to partial functional redundancy with SlCaM6, we generated the Slcam2 Slcam6 double mutant, which showed minimal flower drop under drought. SlCaM2 and SlCaM6 interacted with the transcription factor signal responsive 3L (SlSR3L), with the 3 proteins operating in the same pathway, based on genetic data. We identified Protease inhibitor26 (SlPI26) as a target gene of SlSR3L by DNA affinity purification sequencing and transcriptome analysis. SlPI26 specifically inhibited the activity of the phytaspase SlPhyt2, hence preventing the generation of active phytosulfokine peptide and negatively regulating drought-induced flower drop. SlCaM2 and SlCaM6 enhanced the repression of SlPI26 expression by SlSR3L, promoting drought-induced flower drop. In addition, the nonphototropic hypocotyl3 (SlNPH3)-Cullin3 (SlCUL3) complex, which relies on auxin, interacted with SlSR3L to induce its degradation. However, under drought conditions, SlNPH3-SlCUL3 function is compromised due to lower auxin concentration. These results uncover a regulatory network that precisely controls floral drop in response to drought stress.

Passivation of metal sulfides by a marine bacterium for acid mine drainage control

Acid mine drainage originates from metal sulfides oxidation, which results in acidic metal-rich leachate. In this study, a novel and environmentally friendly approach was demonstrated to passivate pyrite and lead-zinc tailings, respectively. The key to this approach is to develop biofilms of the marine bacterium Qipengyuania flava S1. Biofilms can induce biomineralization, thereby isolating metal sulfides from air and water. The stability and biological toxicity of the bio-passivation layers were evaluated by leaching bio-passivated pyrite or tailings in initially acidic H2O2 solutions with shaking for 180 days and then cultivating Brassica chinensis and Allium cepa with the leachates. Our results showed that after passivation, the amount of iron released by pyrite decreased by at least 99.2 ± 0.2 (in wt%). For lead-zinc tailings after passivation, the released metal ions (Fe+Al+Pb+Zn) decreased by at least 52.0 ± 3.2 (in wt%). The bio-passivation layers also maintained the pH of the leachate in the range of 7.5-8.0. Before bio-passivation, compared with mineral water, the pyrite leachate significantly inhibited the growth of the two plants, and the tailings leachate significantly inhibited the growth of A. cepa, whereas the bio-passivated pyrite or tailings leachate did not show any inhibitory effect.

Genome-Wide Identification and Expression Analysis of ACA/ECAs in Capsicum annuum L

Pepper (Capsicum annuum L.) is a popular vegetable in people's daily lives. During pepper growth, calcium (Ca) is an essential macronutrient, and calcium-transporting ATPase (ACA/ECA) is a vital protein for calcium transport. However, reports on the ACA/ECA gene family in the pepper genome are lacking. Hence, we used various bioinformatics methods to identify the ACA/ECA gene family in pepper. We identified eleven CaACA/ECA-family genes in pepper. The chromosomal distribution, phylogenetic evolution, characteristics, gene collinearity, gene and protein structures, cis-acting elements, and specific expression patterns of CaACA/ECAs were analyzed, revealing evolutionary relationships and correlations between CaACA/ECAs and other species (Arabidopsis, rice, and tomato). The experimental results indicate that CaACA/ECAs are stable and hydrophobic proteins, with each of the eleven CaACA/ECA proteins containing all ten motifs. Eleven CaACA/ECA genes are unevenly distributed on the eight chromosomes, and they substantially differ in the number of exons. We found a close correlation between the ACA/ECAs of pepper, Arabidopsis, and tomato. The CaACA/ECA genes contain various plant-hormone-, growth-, and stress-related cis-acting elements. The qRT-PCR results indicate that the expression levels of the eleven CaACA/ECAs exhibit differential temporal expression patterns under various exogenous Ca2+ concentrations. These results provide a theoretical basis for further studying the function of the pepper ACA/ECA gene family and valuable information for identifying and screening genes for pepper stress tolerance breeding.

CPK10 regulates low light-induced tomato flower drop downstream of IDL6 in a calcium-dependent manner

Flower drop is a major cause for yield loss in many crops. Previously, we found that the tomato (Solanum lycopersicum) INFLORESCENCE DEFICIENT IN ABSCISSION-Like (SlIDL6) gene contributes to flower drop induced by low light. However, the molecular mechanisms by which SlIDL6 acts as a signal to regulate low light-induced abscission remain unclear. In this study, SlIDL6 was found to elevate cytosolic Ca2+ concentrations ([Ca2+]cyt) in the abscission zone (AZ), which was required for SlIDL6-induced flower drop under low light. We further identified that 1 calcium-dependent protein kinase gene, SlCPK10, was highly expressed in the AZ and upregulated by SlIDL6-triggered [Ca2+]cyt. Overexpression and knockout of SlCPK10 in tomato resulted in accelerated and delayed abscission, respectively. Genetic evidence further indicated that knockout of SlCPK10 significantly impaired the function of SlIDL6 in accelerating abscission. Furthermore, Ser-371 phosphorylation in SlCPK10 dependent on SlIDL6 was necessary and sufficient for its function in regulating flower drop, probably by stabilizing the SlCPK10 proteins. Taken together, our findings reveal that SlCPK10, as a downstream component of the IDL6 signaling pathway, regulates flower drop in tomato under low-light stress.

Acidic Stress Induces Cytosolic Free Calcium Oscillation, and an Appropriate Low pH Helps Maintain the Circadian Clock in Arabidopsis

Acidic stress is a formidable environmental factor that exerts adverse effects on plant growth and development, ultimately leading to a potential reduction in agricultural productivity. A low pH triggers Ca2+ influx across the plasma membrane (PM), eliciting distinct responses under various acidic pH levels. However, the underlying mechanisms by which Arabidopsis plant cells generate stimulus-specific Ca2+ signals in response to acidic stress remain largely unexplored. The experimentally induced stimulus may elicit spikes in cytosolic free Ca2+ concentration ([Ca2+]i) spikes or complex [Ca2+]i oscillations that persist for 20 min over a long-term of 24 h or even several days within the plant cytosol and chloroplast. This study investigated the increase in [Ca2+]i under a gradient of low pH stress ranging from pH 3.0 to 6.0. Notably, the peak of [Ca2+]i elevation was lower at pH 4.0 than at pH 3.0 during the initial 8 h, while other pH levels did not significantly increase [Ca2+]i compared to low acidic stress conditions. Lanthanum chloride (LaCl3) can effectively suppress the influx of [Ca2+]i from the apoplastic to the cytoplasm in plants under acid stress, with no discernible difference in intracellular calcium levels observed in Arabidopsis. Following 8 h of acid treatment in the darkness, the intracellular baseline Ca2+ levels in Arabidopsis were significantly elevated when exposed to low pH stress. A moderately low pH, specifically 4.0, may function as a spatial-temporal input into the circadian clock system. These findings suggest that acid stimulation can exert a continuous influence on intracellular calcium levels, as well as plant growth and development.

Regulating programmed cell death in plant cells: Intracellular acidification plays a pivotal role together with calcium signaling

Programmed cell death (PCD) occurs in different tissues in response to a number of different signals in plant cells. Drawing from work in several different contexts, including root-cap cell differentiation, plant response to biotic and abiotic stress, and some self-incompatibility (SI) systems, the data suggest that, despite differences, there are underlying commonalities in the early decision-making stages of PCD. Here, we focus on how 2 cellular events, increased [Ca2+]cyt levels and cytosolic acidification, appear to act as early signals involved in regulating both developmental and stimulus-induced PCD in plant cells.

Sequence-based analysis of the rice CAMTA family: haplotype and network analyses

The calmodulin-binding transcription activator (CAMTA) family contributes to stress responses in many plant species. The Oryza sativa ssp. japonica genome harbors seven CAMTA genes; however, intraspecific variation and functional roles of this gene family have not been determined. Here, we comprehensively evaluated the structure and characteristics of the CAMTA genes in japonica rice using bioinformatics approaches and RT-qPCR. Within the CAMTA gene and promoter sequences, 527 single nucleotide polymorphisms were retrieved from 3,024 rice accessions. The CAMTA genes could be subdivided into 5-14 haplotypes. Association analyses between haplotypes and phenotypic traits, such as grain weight and salt stress parameters, identified phenotypic differences between rice subpopulations harboring different CAMTA haplotypes. Co-expression analyses and the identification of CAMTA-specific binding motifs revealed candidate genes regulated by CAMTA. A Gene Ontology functional enrichment analysis of 690 co-expressed genes revealed that CAMTA genes have key roles in defense responses. An interaction analysis identified 30 putative CAMTA interactors. Three genes were identified in co-expression and interaction network analyses, suggesting that they are potentially regulated by CAMTAs. Based on all information obtained together with the phenotypes of the CRISPR-Cas9 knockout mutant lines of three OskCAMTA genes generated, CAMTA1 likely plays important roles in the response to salt stress in rice. Overall, our findings suggest that the CAMTA gene family is involved in development and the salt stress response and reveal candidate target genes, providing a basis for further functional characterization.

Crosstalk of methylglyoxal and calcium signaling in maize (Zea mays L.) thermotolerance through methylglyoxal-scavenging system

Methylglyoxal (MG) and calcium ion (Ca2+) can increase multiple-stress tolerance including plant thermotolerance. However, whether crosstalk of MG and Ca2+ exists in the formation of maize thermotolerance and underlying mechanism still remain elusive. In this paper, maize seedlings were irrigated with MG and calcium chloride alone or in combination, and then exposed to heat stress (HS). The results manifested that, compared with the survival percentage (SP, 45.3%) of the control seedlings, the SP of MG and Ca2+ alone or in combination was increased to 72.4%, 74.2%, and 83.4% under HS conditions, indicating that Ca2+ and MG alone or in combination could upraise seedling thermotolerance. Also, the MG-upraised SP was separately weakened to 42.2%, 40.3%, 52.1%, and 39.4% by Ca2+ chelator (ethylene glycol tetraacetic acid, EGTA), plasma membrane Ca2+ channel blocker (lanthanum chloride, LaCl3), intracellular Ca2+ channel blocker (neomycin, NEC), and calmodulin (CaM) antagonist (trifluoperazine, TFP). However, significant effect of MG scavengers N-acetylcysteine (NAC) and aminoguanidine (AG) on Ca2+-induced thermotolerance was not observed. Similarly, an endogenous Ca2+ level in seedlings was increased by exogenous MG under non-HS and HS conditions, while exogenous Ca2+ had no significant effect on endogenous MG. These data implied that Ca2+ signaling, at least partly, mediated MG-upraised thermotolerance in maize seedlings. Moreover, the activity and gene expression of glyoxalase system (glyoxalase I, glyoxalase II, and glyoxalase III) and non-glyoxalase system (MG reductase, aldehyde reductase, aldo-keto reductase, and lactate dehydrogenase) were up-regulated to a certain extent by Ca2+ and MG alone in seedlings under non-HS and HS conditions. The up-regulated MG-scavenging system by MG was enhanced by Ca2+, while impaired by EGTA, LaCl3, NEC, or TFP. These data suggest that the crosstalk of MG and Ca2+ signaling in maize thermotolerance through MG-scavenging system. These findings provided a theoretical basis for breeding climate-resilient maize crop and developing smart agriculture.

Small molecule, big impacts: Nano-nutrients for sustainable agriculture and food security

Human existence and the long-term viability of society depend on agriculture. Overuse of synthetic fertilizers results in increased contamination of the land, water, and atmosphere as well as financial constraints. In today's modern agriculture, environmentally friendly technology is becoming more and more significant as a substitute for conventional fertilizers and chemical pesticides. Using nanotechnology, agricultural output can be improved in terms of quality, biological support, financial stability, and environmental safety. There is a lot of promise for the sustainable application of nano-fertilizers in crop productivity and soil fertility, with little or no negative environmental effects. In this context, the present review provided an overview of the benefits of using nanofertilizers, its application and types. Mechanistic approach for increasing soil fertility and yield via nanofertilizers also described in detail. We concluded this article to compare the advantages of nanofertilizers over chemicals and nano-chemicals. Nonetheless, additional investigation is required to comprehend the effects and possible hazards of nanomaterials in the food production chain.

Two calcium sensor-activated kinases function in root hair growth

Plant pollen tubes and root hairs typically polarized tip growth. It is well established that calcium ions (Ca2+) play essential roles in maintaining cell polarity and guiding cell growth orientation. Ca2+ signals are encoded by Ca2+ channels and transporters and are decoded by a variety of Ca2+-binding proteins often called Ca2+ sensors, in which calcineurin B-like protein (CBL) proteins function by interacting with and activating a group of kinases and activate CBL-interacting protein kinases (CIPKs). Some CBL-CIPK complexes, such as CBL2/3-CIPK12/19, act as crucial regulators of pollen tube growth. Whether these calcium decoding components regulate the growth of root hairs, another type of plant cell featuring Ca2+-regulated polarized growth, remains unknown. In this study, we identified CIPK13 and CIPK18 as genes specifically expressed in Arabidopsis (Arabidopsis thaliana) root hairs. The cipk13 cipk18 double mutants showed reduced root hair length and lower growth rates. The calcium oscillations at the root hair tip were attenuated in the cipk13 cipk18 mutants as compared to the wild-type plants. Through yeast 2-hybrid screens, CBL2 and CBL3 were identified as interacting with CIPK13 and CIPK18. cbl2 cbl3 displayed a shortened root hair phenotype similar to cipk13 cipk18. This genetic analysis, together with biochemical assays showing activation of CIPK13/18 by CBL2/3, supported the conclusion that CBL2/3 and CIPK13/18 may work as Ca2+-decoding modules in controlling root hair growth. Thus, the findings that CIPK12/19 and CIPK13/18 function in pollen tube and root hair growth, respectively, illustrate a molecular mechanism in which the same CBLs recruit distinct CIPKs in regulating polarized tip growth in different types of plant cells.

The Ubiquitous Wilt-Inducing Pathogen Fusarium oxysporum-A Review of Genes Studied with Mutant Analysis

Fusarium oxysporum is one of the most economically important plant fungal pathogens, causing devastating Fusarium wilt diseases on a diverse range of hosts, including many key crop plants. Consequently, F. oxysporum has been the subject of extensive research to help develop and improve crop protection strategies. The sequencing of the F. oxysporum genome 14 years ago has greatly accelerated the discovery and characterization of key genes contributing to F. oxysporum biology and virulence. In this review, we summarize important findings on the molecular mechanisms of F. oxysporum growth, reproduction, and virulence. In particular, we focus on genes studied through mutant analysis, covering genes involved in diverse processes such as metabolism, stress tolerance, sporulation, and pathogenicity, as well as the signaling pathways that regulate them. In doing so, we hope to present a comprehensive review of the molecular understanding of F. oxysporum that will aid the future study of this and related species.

The Ca2+-Regulated Protein Kinase CIPK1 Modulates Plant Response to Nitrate Deficiency in Arabidopsis

BACKGROUND/OBJECTIVES

Nitrogen is an essential macroelement for plant growth and productivity. Calcium (Ca2+) acts as a critical second messenger in numerous adaptations and developmental processes in plants. The Calcineurin B-like protein (CBL)-interacting protein kinase (CIPK) signaling pathway has been demonstrated to be involved in multiple intracellular ion homeostasis of plants in response to stresses. However, whether CIPKs are involved in nitrate deficiency stress remains largely unknown.

METHODS

In this study, we screened Arabidopsis thaliana T-DNA insertion mutants of the CIPK family under nitrate deficiency conditions by a reverse genetic strategy.

RESULTS

We found that the cipk1 mutant showed a shorter primary root and had a lower fresh weight and total N content compared with wildtype (WT) plants under nitrate deficiency. The CIPK1 complementation lines completely rescued the sensitive phenotype. Additionally, CIPK1 mutation caused nitrogen-starvation marker genes to be decreased under nitrate deficiency. We further found that CIPK1 interacted with teosintebranched 1/cycloidea/proliferating cell factor 1-20 (TCP20) in a yeast two-hybrid system.

CONCLUSIONS

Collectively, our results reveal a novel role of CIPK1 in response to nitrate deficiency in Arabidopsis.

Internal Disorders of Mango Fruit and Their Management-Physiology, Biochemistry, and Role of Mineral Nutrients

Mango (Mangifera indica L.) is a popular fruit grown in tropical and subtropical regions. Mango has a distinctive aroma, flavour, and nutritional properties. Annual global mango production is >50 million tonnes. Major producers of mango include India, Bangladesh, China, Mexico, Pakistan, Indonesia, Brazil, Thailand, and the Philippines, and it is shipped worldwide. Harvested mango fruit are highly perishable, with a short shelf life. Physiological disorders are among the major factors limiting their postharvest quality and shelf life, including when fruit need phytosanitary treatments, such as hot water treatment, vapour heat treatment, and irradiation. This review focuses on problematic physiological disorders of mango flesh, including physiology and biochemistry. It considers factors contributing to the development and/or exacerbation of internal disorders. Improved production practices, including pruning, nutrient application, and irrigation, along with monitoring and managing environmental conditions (viz., temperature, humidity, and vapour pressure deficit), can potentially maintain fruit robustness to better tolerate otherwise stressful postharvest operations. As demand for mangoes on international markets is compromised by internal quality, robust fruit is crucial to maintaining existing and gaining new domestic and export consumer markets. Considering mango quality, a dynamic system, a more holistic approach encompassing pre-, at-, and post-harvest conditions as a continuum is needed to determine fruit predisposition and subsequent management of internal disorders.

Effects of calcium ions and cell wall deposition on the pollen viability of Paeonia lactiflora after cryopreservation

MAIN CONCLUSION

Four cultivars of Paeonia lactiflora pollen have a different viability after cryopreservation, and that the difference of pollen viability is related to calcium ions and cell wall deposition. Cryopreservation is a vital technique for preserving germplasm resources, offering extensive application prospects. Understanding the factors influencing pollen viability after cryopreservation is crucial for the permanent preservation and exchange of pollen resources. This study investigated pollen from four Paeonia lactiflora cultivars with varying viability after cryopreservation, aiming to determine whether calcium ions (Ca2+) and cell wall deposition affect these viability changes. The results showed that Ca2+-ATPase activity and cytoplasmic Ca2+ of all four cultivars exhibited an increasing trend after cryopreservation; the calmodulin (CaM) content varied with cultivars. Correlation analysis showed that fresh pollen viability was significantly negatively correlated with cytoplasmic Ca2+ content and positively correlated with Ca2+-ATPase activity, while pollen viability after cryopreservation exhibited a significantly negative correlation with cytoplasmic Ca2+ content and a positive correlation with CaM content. The pollen cell wall of the cultivar 'Zi Feng Chao Yang' (ZFCY), which showed increased viability after cryopreservation, contained significantly higher levels of low-temperature tolerance-related phospholipids and proteins compared to other cultivars. Additionally, all cultivars maintained a clear Ca2+ gradient at the tips of pollen tubes after cryopreservation, without significant callose accumulation. These findings suggest that differences in Ca2+ signaling and cell wall components deposition influence changes in pollen viability after cryopreservation, and the Ca2+ gradient and callose at the tip of pollen tubes are not responsible for preventing pollen tube growth.

Natural allelic diversity of the calcium signaling regulators in plants

Calcium ions act as secondary messengers in diverse signaling pathways in plants throughout their life cycle. Studies have revealed that calcium is involved in developmental events and in responses to external stimuli, such as biotic and abiotic stresses. Cellular calcium ion levels are tightly controlled by intricate molecular machinery such as calcium channels and pumps. Transient and spatial fluctuations in calcium levels are subsequently recognized by diverse calcium-decoding molecules, resulting in signal transduction. In this review, we highlight recent findings on natural variations in genes controlling calcium signaling in diverse plant biological processes. We then show how the calcium ion context is utilized by fine-tuning the natural variation in centrally important genes.

Probing plant signal processing optogenetically by two channelrhodopsins

Early plant responses to different stress situations often encompass cytosolic Ca2+ increases, plasma membrane depolarization and the generation of reactive oxygen species1-3. However, the mechanisms by which these signalling elements are translated into defined physiological outcomes are poorly understood. Here, to study the basis for encoding of specificity in plant signal processing, we used light-gated ion channels (channelrhodopsins). We developed a genetically engineered channelrhodopsin variant called XXM 2.0 with high Ca2+ conductance that enabled triggering cytosolic Ca2+ elevations in planta. Plant responses to light-induced Ca2+ influx through XXM 2.0 were studied side by side with effects caused by an anion efflux through the light-gated anion channelrhodopsin ACR1 2.04. Although both tools triggered membrane depolarizations, their activation led to distinct plant stress responses: XXM 2.0-induced Ca2+ signals stimulated production of reactive oxygen species and defence mechanisms; ACR1 2.0-mediated anion efflux triggered drought stress responses. Our findings imply that discrete Ca2+ signals and anion efflux serve as triggers for specific metabolic and transcriptional reprogramming enabling plants to adapt to particular stress situations. Our optogenetics approach unveiled that within plant leaves, distinct physiological responses are triggered by specific ion fluxes, which are accompanied by similar electrical signals.

Response Mechanisms of Zelkova schneideriana Leaves to Varying Levels of Calcium Stress

Calcium stress can negatively impact plant growth, prompting plants to respond by mitigating this effect. However, the specific mechanisms underlying this response remain unclear. In this study, we used non-targeted metabolomics and transcriptomics to investigate the response mechanisms of Zelkova schneideriana leaves under varying degrees of calcium stress. Results revealed that calcium stress led to wilt in young leaves. When calcium stress exceeds the tolerance threshold of the leaf, it results in wilting of mature leaves, rupture of chloroplasts in palisade tissue, and extensive wrinkling and breakage of leaf cells. Transcriptomic analysis indicated that calcium stress inhibited photosynthesis by suppressing the expression of genes related to photosynthetic system II and electron transport. Leaf cells activate phenylpropanoid biosynthesis, flavonoid biosynthesis, and Vitamin B6 metabolism to resist calcium stress. When calcium accumulation gradually surpassed the tolerance threshold of the cells, this results in failure of conventional anti-calcium stress mechanisms, leading to cell death. Furthermore, excessive calcium stress inhibits the expression of CNGC and anti-pathogen genes. The results of the metabolomics study showed that five key metabolites increased in response to calcium stress, which may play an important role in countering calcium stress. This study provides insights into the response of Z. schneideriana leaves to different levels of calcium stress, which could provide a theoretical basis for cultivating Z. schneideriana in karst areas and enhance our understanding of plant responses to calcium stress.

Overexpression of tonoplast Ca2+-ATPase in guard cells synergistically enhances stomatal opening and drought tolerance

Stomata play a crucial role in plants by controlling water status and responding to drought stress. However, simultaneously improving stomatal opening and drought tolerance has proven to be a significant challenge. To address this issue, we employed the OnGuard quantitative model, which accurately represents the mechanics and coordination of ion transporters in guard cells. With the guidance of OnGuard, we successfully engineered plants that overexpressed the main tonoplast Ca2+-ATPase gene, ACA11, which promotes stomatal opening and enhances plant growth. Surprisingly, these transgenic plants also exhibited improved drought tolerance due to reduced water loss through their stomata. Again, OnGuard assisted us in understanding the mechanism behind the unexpected stomatal behaviors observed in the ACA11 overexpressing plants. Our study revealed that the overexpression of ACA11 facilitated the accumulation of Ca2+ in the vacuole, thereby influencing Ca2+ storage and leading to an enhanced Ca2+ elevation in response to abscisic acid. This regulatory cascade finely tunes stomatal responses, ultimately leading to enhanced drought tolerance. Our findings underscore the importance of tonoplast Ca2+-ATPase in manipulating stomatal behavior and improving drought tolerance. Furthermore, these results highlight the diverse functions of tonoplast-localized ACA11 in response to different conditions, emphasizing its potential for future applications in plant enhancement.

Canola (Brassica napus) enhances sodium chloride and sodium ion tolerance by maintaining ion homeostasis, higher antioxidant enzyme activity and photosynthetic capacity fluorescence parameters

Under salt stress, plants are forced to take up and accumulate large amounts of sodium (Na+ ) and chloride (Cl- ). Although most studies have focused on the toxic effects of Na+ on plants, Cl- stress is also very important. This study aimed to clarify physiological mechanisms underpinning growth contrasts in canola varieties with different salt tolerance. In hydroponic experiments, 150mM Na+ , Cl- and NaCl were applied to salt-tolerant and sensitive canola varieties. Both NaCl and Na+ treatments inhibited seedling growth. NaCl caused the strongest damage to both canola varieties, and stress damage was more severe at high concentrations of Na+ than Cl- . High Cl- promoted the uptake of ions (potassium K+ , calcium Ca2+ ) and induced antioxidant defence. Salt-tolerant varieties were able to mitigate ion toxicity by maintaining lower Na+ content in the root system for a short period of time, and elevating magnesium Mg2+ content, Mg2+ /Na+ ratio, and antioxidant enzyme activity to improve photosynthetic capacity. They subsequently re-established new K+ /Na+ and Ca2+ /Na+ balances to improve their salt tolerance. High concentrations of Cl salts caused less damage to seedlings than NaCl and Na salts, and Cl- also had a positive role in inducing oxidative stress and responsive antioxidant defence in the short term.

Pectin-associated immune responses in plant-microbe interactions: A review

This review explores the role of pectin, a complex polysaccharide found in the plant cell wall, in mediating immune responses during interactions between plants and microbes. The objectives of this study were to investigate the molecular mechanisms underlying pectin-mediated immune responses and to understand how these interactions shape plant-microbe communication. Pectin acts as a signaling molecule, triggering immune responses such as the production of antimicrobial compounds, reinforcement of the cell wall, and activation of defense-related genes. Pectin functions as a target for pathogen-derived enzymes, enabling successful colonization by certain microbial species. The document discusses the complexity of pectin-based immune signaling networks and their modulation by various factors, including pathogen effectors and host proteins. It also emphasizes the importance of understanding the crosstalk between pectin-mediated immunity and other defense pathways to develop strategies for enhancing plant resistance against diseases. The insights gained from this study have implications for the development of innovative approaches to enhance crop protection and disease management in agriculture. Further investigations into the components and mechanisms involved in pectin-mediated immunity will pave the way for future advancements in plant-microbe interaction research.

Functional validation of AaCaM3 response to high temperature stress in Amorphophallus albus

Amorphophallus is a perennial monocotyledonous herbaceous plant native to the southwestern region of China, widely used in various fields such as food processing, biomedicine and chemical agriculture. However, Amorphophallus is a typical thermolabile plant, and the continuous high temperature in summer have seriously affected the growth, development and economic yield of Amorphophallus in recent years. Calmodulin (CaM), a Ca2+ sensor ubiquitous in eukaryotes, is the most important multifunctional receptor protein in plant cells, which affects plant stress resistance by participating in the activities of a variety of signaling molecules. In this study, the key gene AaCaM3 for the Ca2+-CaM regulatory pathway was obtained from A. albus, the sequence analysis confirmed that it is a typical calmodulin. The qRT-PCR results demonstrated that with the passage of heat treatment time, the expression of AaCaM3 was significantly upregulated in A. albus leaves. Subcellular localization analysis revealed that AaCaM3 localized on the cytoplasm and nucleus. Meanwhile, heterologous transformation experiments have shown that AaCaM3 can significantly improve the heat tolerance of Arabidopsis under heat stress. The promoter region of AaCaM3 was sequenced 1,338 bp by FPNI-PCR and GUS staining assay showed that the promoter of AaCaM3 was a high-temperature inducible promoter. Yeast one-hybrid analysis and Luciferase activity reporting system analysis showed that the AaCaM3 promoter may interact with AaHSFA1, AaHSFA2c, AaHSP70, AaDREB2a and AaDREB2b. In conclusion, this study provides new ideas for further improving the signal transduction network of high-temperature stress in Amorphophallus.

Vitamin D, the Sunshine Molecule That Makes Us Strong: What Does Its Current Global Deficiency Imply?

Vitamin D3 deficiency and insufficiency are becoming a common global issue for us, especially in the most industrially developed countries. The only acknowledged activity of vitamin D3 in vertebrates is to promote the absorption of calcium and, therefore, allow for the mineralization of bones. Accordingly, its deficiency is associated with diseases such as rickets. Other numerous vital functions associated with vitamin D3 are yet to be considered, and the function of vitamin D2 in plants is unknown. Thus, 100 years after its discovery, the importance of vitamin D still seems to be unacknowledged (except for rickets), with little attention given to its decrease throughout the world. In this review, I suggest that vitamin D deficiency and insufficiency may be linked to the westernized lifestyle in more developed countries. Furthermore, I suggest that, rather than the calcemic activity, the main function of vitamin D is, in general, that of strengthening living organisms. I conclude with the hypothesis that vitamin D deficiency may represent a marker for a greater risk of chronic inflammatory diseases and a shorter life expectancy.

Integrated Assays of Genome-Wide Association Study, Multi-Omics Co-Localization, and Machine Learning Associated Calcium Signaling Genes with Oilseed Rape Resistance to Sclerotinia sclerotiorum

Sclerotinia sclerotiorum (Ss) is one of the most devastating fungal pathogens, causing huge yield loss in multiple economically important crops including oilseed rape. Plant resistance to Ss pertains to quantitative disease resistance (QDR) controlled by multiple minor genes. Genome-wide identification of genes involved in QDR to Ss is yet to be conducted. In this study, we integrated several assays including genome-wide association study (GWAS), multi-omics co-localization, and machine learning prediction to identify, on a genome-wide scale, genes involved in the oilseed rape QDR to Ss. Employing GWAS and multi-omics co-localization, we identified seven resistance-associated loci (RALs) associated with oilseed rape resistance to Ss. Furthermore, we developed a machine learning algorithm and named it Integrative Multi-Omics Analysis and Machine Learning for Target Gene Prediction (iMAP), which integrates multi-omics data to rapidly predict disease resistance-related genes within a broad chromosomal region. Through iMAP based on the identified RALs, we revealed multiple calcium signaling genes related to the QDR to Ss. Population-level analysis of selective sweeps and haplotypes of variants confirmed the positive selection of the predicted calcium signaling genes during evolution. Overall, this study has developed an algorithm that integrates multi-omics data and machine learning methods, providing a powerful tool for predicting target genes associated with specific traits. Furthermore, it makes a basis for further understanding the role and mechanisms of calcium signaling genes in the QDR to Ss.

Sugarcane ScCAX4 is a Negative Regulator of Resistance to Pathogen Infection

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.

Impact of translational regulation on diel expression revealed by time-series ribosome profiling in Arabidopsis

Plants have developed the ability to adjust to the day/night cycle through the expression of diel genes, which allow them to effectively respond to environmental changes and optimise their growth and development. Diel oscillations also have substantial implications in many physiological processes, including photosynthesis, floral development, and environmental stress responses. The expression of diel genes is regulated by a combination of the circadian clock and responses to environmental cues, such as light and temperature. A great deal of information is available on the transcriptional regulation of diel gene expression. However, the extent to which translational regulation is involved in controlling diel changes in expression is not yet clear. To investigate the impact of translational regulation on diel expression, we conducted Ribo-seq and RNA-seq analyses on a time-series sample of Arabidopsis shoots cultivated under a 12 h light/dark cycle. Our results showed that translational regulation is involved in about 71% of the genes exhibiting diel changes in mRNA abundance or translational activity, including clock genes, many of which are subject to both translational and transcriptional control. They also revealed that the diel expression of glycosylation and ion-transporter-related genes is mainly established through translational regulation. The expression of several diel genes likely subject to translational regulation through upstream open-reading frames was also determined.

Genome-wide identification of the CNGC gene family and negative regulation of drought tolerance by HvCNGC3 and HvCNGC16 in transgenic Arabidopsis thaliana

Cyclic nucleotide-gated ion channels (CNGCs), as non-selective cation channels, play essential roles in plant growth and stress responses. However, they have not been identified in Qingke (Hordeum vulgare L.). Here, we performed a comprehensive genome-wide identification and function analysis of the HvCNGC gene family to determine its role in drought tolerance. Phylogenetic analysis showed that 27 HvCNGC genes were divided into four groups and unevenly located on seven chromosomes. Transcription analysis revealed that two closely related members of HvCNGC3 and HvCNGC16 were highly induced and the expression of both genes were distinctly different in two extremely drought-tolerant materials. Transient expression revealed that the HvCNGC3 and HvCNGC16 proteins both localized to the plasma membrane and karyotheca. Overexpression of HvCNGC3 and HvCNGC16 in Arabidopsis thaliana led to impaired seed germination and seedling drought tolerance, which was accompanied by higher hydrogen peroxide (H2O2), malondialdehyde (MDA), proline accumulation and increased cell damage. In addition, HvCNGC3 and HvCNGC16-overexpression lines reduced ABA sensitivity, as well as lower expression levels of some ABA biosynthesis and stress-related gene in transgenic lines. Furthermore, Yeast two hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays revealed that HvCNGC3 and HvCNGC16 interacted with calmodulin/calmodulin-like proteins (CaM/CML), which, as calcium sensors, participate in the perception and decoding of intracellular calcium signaling. Thus, this study provides information on the CNGC gene family and provides insight into the function and potential regulatory mechanism of HvCNGC3 and HvCNGC16 in drought tolerance in Qingke.

CAMTA3 repressor destabilization triggers TIR domain protein TN2-mediated autoimmunity in the Arabidopsis exo70B1 mutant

Calcium-dependent protein kinases (CPKs) can decode and translate intracellular calcium signals to induce plant immunity. Mutation of the exocyst subunit gene EXO70B1 causes autoimmunity that depends on CPK5 and the Toll/interleukin-1 receptor (TIR) domain resistance protein TIR-NBS2 (TN2), where direct interaction with TN2 stabilizes CPK5 kinase activity. However, how the CPK5-TN2 interaction initiates downstream immune responses remains unclear. Here, we show that, besides CPK5 activity, the physical interaction between CPK5 and functional TN2 triggers immune activation in exo70B1 and may represent reciprocal regulation between CPK5 and the TIR domain functions of TN2 in Arabidopsis (Arabidopsis thaliana). Moreover, we detected differential phosphorylation of the calmodulin-binding transcription activator 3 (CAMTA3) in the cpk5 background. CPK5 directly phosphorylates CAMTA3 at S964, contributing to its destabilization. The gain-of-function CAMTA3A855V variant that resists CPK5-induced degradation rescues immunity activated through CPK5 overexpression or exo70B1 mutation. Thus, CPK5-mediated immunity is executed through CAMTA3 repressor degradation via phosphorylation-induced and/or calmodulin-regulated processes. Conversely, autoimmunity in camta3 also partially requires functional CPK5. While the TIR domain activity of TN2 remains to be tested, our study uncovers a TN2-CPK5-CAMTA3 signaling module for exo70B1-mediated autoimmunity, highlighting the direct embedding of a calcium-sensing decoder element within resistance signalosomes.

The complex transcriptional regulation of heat stress response in maize

As one of the most important food and feed crops worldwide, maize suffers much more tremendous damages under heat stress compared to other plants, which seriously inhibits plant growth and reduces productivity. To mitigate the heat-induced damages and adapt to high temperature environment, plants have evolved a series of molecular mechanisms to sense, respond and adapt high temperatures and heat stress. In this review, we summarized recent advances in molecular regulations underlying high temperature sensing, heat stress response and memory in maize, especially focusing on several important pathways and signals in high temperature sensing, and the complex transcriptional regulation of ZmHSFs (Heat Shock Factors) in heat stress response. In addition, we highlighted interactions between ZmHSFs and several epigenetic regulation factors in coordinately regulating heat stress response and memory. Finally, we laid out strategies to systematically elucidate the regulatory network of maize heat stress response, and discussed approaches for breeding future heat-tolerance maize.

Channels of Evolution: Unveiling Evolutionary Patterns in Diatom Ca2+ Signalling

Diatoms are important primary producers in marine and freshwater environments, but little is known about the signalling mechanisms they use to detect changes in their environment. All eukaryotic organisms use Ca2+ signalling to perceive and respond to environmental stimuli, employing a range of Ca2+-permeable ion channels to facilitate the movement of Ca2+ across cellular membranes. We investigated the distribution of different families of Ca2+ channels in diatom genomes, with comparison to other members of the stramenopile lineage. The four-domain voltage-gated Ca2+ channels (Cav) are present in some centric diatoms but almost completely absent in pennate diatoms, whereas single-domain voltage-gated EukCatA channels were found in all diatoms. Glutamate receptors (GLRs) and pentameric ligand-gated ion channels (pLGICs) also appear to have been lost in several pennate species. Transient receptor potential (TRP) channels are present in all diatoms, but have not undergone the significant expansion seen in brown algae. All diatom species analysed lacked the mitochondrial uniporter (MCU), a highly conserved channel type found in many eukaryotes, including several stramenopile lineages. These results highlight the unique Ca2+-signalling toolkit of diatoms and indicate that evolutionary gains or losses of different Ca2+ channels may contribute to differences in cellular-signalling mechanisms between species.

Functional differentiation and genetic diversity of rice cation exchanger (CAX) genes and their potential use in rice improvement

Cation exchanger (CAX) genes play an important role in plant growth/development and response to biotic and abiotic stresses. Here, we tried to obtain important information on the functionalities and phenotypic effects of CAX gene family by systematic analyses of their expression patterns, genetic diversity (gene CDS haplotypes, structural variations, gene presence/absence variations) in 3010 rice genomes and nine parents of 496 Huanghuazhan introgression lines, the frequency shifts of the predominant gcHaps at these loci to artificial selection during modern breeding, and their association with tolerances to several abiotic stresses. Significant amounts of variation also exist in the cis-regulatory elements (CREs) of the OsCAX gene promoters in 50 high-quality rice genomes. The functional differentiation of OsCAX gene family were reflected primarily by their tissue and development specific expression patterns and in varied responses to different treatments, by unique sets of CREs in their promoters and their associations with specific agronomic traits/abiotic stress tolerances. Our results indicated that OsCAX1a and OsCAX2 as general signal transporters were in many processes of rice growth/development and responses to diverse environments, but they might be of less value in rice improvement. OsCAX1b, OsCAX1c, OsCAX3 and OsCAX4 was expected to be of potential value in rice improvement because of their associations with specific traits, responsiveness to specific abiotic stresses or phytohormones, and relatively high gcHap and CRE diversity. Our strategy was demonstrated to be highly efficient to obtain important genetic information on genes/alleles of specific gene family and can be used to systematically characterize the other rice gene families.