Plant Signaling Research Articles

Interplant communication increases aphid resistance and alters rhizospheric microbes in neighboring plants of aphid-infested cucumbers.

Aphis gossypii Glover is a prevalent phytophagous insect that inflicts significant damage on cucumber plants. Recent studies have provided insights into plant communication and signal transduction within conspecifics. However, understanding of the effect of these communication mechanisms on adjacent cucumbers and their resident aphids, especially in the context of an aphid infestation, is still in its early stages. Utilizing a partitioned root configuration, a tendency for aphids to gather on nearby cucumber leaves of non-infested plants was observed. Furthermore, neighboring plants near aphid-infested cucumber plants showed a reduction in aphid reproduction rates. Concurrently, these plants exhibited a significant increase in reactive oxygen species (ROS) levels, along with enhanced defensive and antioxidant enzymatic responses. Analysis of the microbial community in the rhizosphere showed significant differences in species composition among the samples. Among these, the bacterial families Microbacteriaceae and Rhizobiaceae, along with the fungal species Leucocoprinus ianthinus and Mortierella globalpina, exhibited increases in their relative abundance in cucumber seedlings located near aphid-infested plants. Significantly, this study unveiled robust correlations between dominant microbial phyla and physiological indicators, primarily associated with aphid resistance mechanisms in plants. The results show that aphid-infested cucumber plants trigger oxidative stress responses in adjacent seedlings through complex interplant communication mechanisms. In addition, these plants cause changes in the composition of the rhizospheric microbial community and the physiological activity of neighboring plants, consequently boosting their natural resistance to aphids. This study provides essential theoretical foundations to guide the development of sustainable strategies for managing cucumber aphids. © 2024 Society of Chemical Industry.

Transcriptome analysis revealed the effect of ethylene on grape buds and leaves

ABSTRACT Ethylene is one of the important endogenous gaseous plant hormones that regulates various metabolic and developmental processes in plants. In this study, we found that ethylene could promote bud break and improve the antioxidant system in buds, whereas ethylene increased the chlorophyll and carotenoid degradation that led to the leaves senescence. RNA-seq was also used to analyse the grape leaves and buds treated with ethylene. A total of 7457 differentially expressed genes were identified in the two comparison samples. The annotation results showed that differential genes in GO and KEGG were mainly involved in plant hormone biosynthesis, signal transduction, photosynthesis, and secondary metabolism. We developed a possible model for ethylene controlling and senescence of the leaf and the bud dormancy based on the data produced in RNA-seq. It is evident that exogenous ethylene promoted leaf senescence by regulating various hormone signals, particularly ABA, and inhibiting photosynthesis. Compared with leaves, exogenous ethylene tended to promote photosynthesis in buds and secondary metabolism to regulate buds dormancy. This study will be helpful to clarify the possible action mechanism of ethylene regulating the development of leaves and buds.

Modeling the reactive oxygen species (ROS) wave in Chlamydomonas reinhardtii colonies

Reactive oxygen species (ROS) play a crucial role as signaling molecules in both plant and animal cells, enabling rapid responses to various stimuli. Among the many cellular mechanisms used to generate and transduce ROS signals, ROS-induced-ROS release (RIRR) is emerging as an important pathway involved in the responses of various multicellular and unicellular organisms to environmental stresses. In RIRR, one cellular compartment, organelle, or cell generates or releases ROS, triggering an increased ROS production and release by another compartment, organelle, or cell, thereby giving rise to a fast propagating ROS wave. This RIRR-based signal relay has been demonstrated to facilitate mitochondria-to-mitochondria communication in animal cells and long-distance systemic signaling in plants in response to biotic and abiotic stresses. More recently, it has been discovered that different unicellular microorganism communities also exhibit a RIRR cell-to-cell signaling process triggered by a localized stress treatment. However, the precise mechanism underlying the propagation of the ROS signal among cells within these unicellular communities remained elusive. In this study, we employed a reaction-diffusion model incorporating the RIRR mechanism to analyze the propagation of ROS-mediated signals. By effectively balancing production and scavenging processes, our model successfully reproduces the experimental ROS signal velocities observed in unicellular green algae (Chlamydomonas reinhardtii) colonies grown on agar plates, furthering our understanding of intercellular ROS communication.

Genome-editing of a circadian clock gene TaPRR95 facilitates wheat peduncle growth and heading date

Plant height and heading date are important agronomic traits in wheat (Triticum aestivum L.) that affect final grain yield. In wheat, knowledge of pseudo-response regulator (PRR) genes on agronomic traits is limited. Here, we identify a wheat TaPRR95 gene by genome-wide association study to be associated with plant height. Triple allele mutant plants produced by CRISPR/Cas9 show increased plant height, particularly the peduncle, with an earlier heading date. The longer peduncle is mainly caused by the increased cell elongation at its upper section, whilst the early heading date is accompanied by elevated expression of flowering genes, such as TaFT and TaCO1. A peduncle-specific transcriptome analysis reveals up-regulated photosynthesis genes and down-regulated IAA/Aux genes for auxin signaling in prr95aabbdd plants that may act as a regulatory mechanism to promote robust plant growth. A haplotype analysis identifies a TaPRR95-B haplotype (Hap2) to be closely associated with reduced plant height and increased thousand-grain weight. Moreover, the Hap2 frequency is higher in cultivars than that in landraces, suggesting the artificial selection on the allele during wheat breeding. These findings suggest that TaPRR95 is a regulator for plant height and heading date, thereby providing an important target for wheat yield improvement.

GhMPK9-GhRAF39_1-GhWRKY40a Regulates the GhERF1b- and GhABF2-Mediated Pathways to Increase Cotton Disease Resistance.

Mitogen-activated protein kinase (MAPK) cascade is the center of plant signal transduction system that amplify immune signals into cellular responses by phosphorylating diverse substrates. The MAPK cascade consisting of MAPK kinase kinases (MAPKKKs), MAPK kinases (MAPKKs), and MAPKs is well characterized in plants, in which Raf-like kinases are generally regarded as MAPKKKs. However, it is rarely reported that Raf-like MAPKKKs function as middle regulators to link MAPK and its downstream transcription factors in plant immunity. Verticillium wilt, caused by the soil-borne vascular fungus Verticillium dahliae, is a serious disease in many plants, including cotton. The previous studies showed that GhMPK9 (a MAPK) is involved in the response to Verticillium wilt. Here, the Raf-like kinase GhRAF39_1 is reported as helper regulates the phosphorylation of WRKY transcription factor GhWRKY40a by GhMPK9. The phosphorylated GhWRKY40a can further activate the transcription of GhERF1b to up-regulate defense-related genes while inhibit the transcription of GhABF2 to regulate the stomatal opening, thus improving the resistance to Verticillium wilt in cotton. This study reveals a new signaling module of GhMPK9-GhRAF39_1-GhWRKY40a to regulate GhERF1b- and GhABF2-mediated defense responses, which triggers plant defense against Verticillium wilt.

Phospholipid Signaling in Crop Plants: A Field to Explore.

In plant models such as Arabidopsis thaliana, phosphatidic acid (PA), a key molecule of lipid signaling, was shown not only to be involved in stress responses, but also in plant development and nutrition. In this article, we highlight lipid signaling existing in crop species. Based on open access databases, we update the list of sequences encoding phospholipases D, phosphoinositide-dependent phospholipases C, and diacylglycerol-kinases, enzymes that lead to the production of PA. We show that structural features of these enzymes from model plants are conserved in equivalent proteins from selected crop species. We then present an in-depth discussion of the structural characteristics of these proteins before focusing on PA binding proteins. For the purpose of this article, we consider RESPIRATORY BURST OXIDASE HOMOLOGUEs (RBOHs), the most documented PA target proteins. Finally, we present pioneering experiments that show, by different approaches such as monitoring of gene expression, use of pharmacological agents, ectopic over-expression of genes, and the creation of silenced mutants, that lipid signaling plays major roles in crop species. Finally, we present major open questions that require attention since we have only a perception of the peak of the iceberg when it comes to the exciting field of phospholipid signaling in plants.

Nanoparticles as a Tool for Alleviating Plant Stress: Mechanisms, Implications, and Challenges.

Plants, being sessile, are continuously exposed to varietal environmental stressors, which consequently induce various bio-physiological changes in plants that hinder their growth and development. Oxidative stress is one of the undesirable consequences in plants triggered due to imbalance in their antioxidant defense system. Biochemical studies suggest that nanoparticles are known to affect the antioxidant system, photosynthesis, and DNA expression in plants. In addition, they are known to boost the capacity of antioxidant systems, thereby contributing to the tolerance of plants to oxidative stress. This review study attempts to present the overview of the role of nanoparticles in plant growth and development, especially emphasizing their role as antioxidants. Furthermore, the review delves into the intricate connections between nanoparticles and plant signaling pathways, highlighting their influence on gene expression and stress-responsive mechanisms. Finally, the implications of nanoparticle-assisted antioxidant strategies in sustainable agriculture, considering their potential to enhance crop yield, stress tolerance, and overall plant resilience, are discussed.

Revisiting the Role of Sensors for Shaping Plant Research: Applications and Future Perspectives.

Plant health monitoring is essential for understanding the impact of environmental stressors (biotic and abiotic) on crop production, and for tailoring plant developmental and adaptive responses accordingly. Plants are constantly exposed to different stressors like pathogens and soil pollutants (heavy metals and pesticides) which pose a serious threat to their survival and to human health. Plants have the ability to respond to environmental stressors by undergoing rapid transcriptional, translational, and metabolic reprogramming at different cellular compartments in order to balance growth and adaptive responses. However, plants' exceptional responsiveness to environmental cues is highly complex, which is driven by diverse signaling molecules such as calcium Ca2+, reactive oxygen species (ROS), hormones, small peptides and metabolites. Additionally, other factors like pH also influence these responses. The regulation and occurrence of these plant signaling molecules are often undetectable, necessitating nondestructive, live research approaches to understand their molecular complexity and functional traits during growth and stress conditions. With the advent of sensors, in vivo and in vitro understanding of some of these processes associated with plant physiology, signaling, metabolism, and development has provided a novel platform not only for decoding the biochemical complexity of signaling pathways but also for targeted engineering to improve diverse plant traits. The application of sensors in detecting pathogens and soil pollutants like heavy metal and pesticides plays a key role in protecting plant and human health. In this review, we provide an update on sensors used in plant biology for the detection of diverse signaling molecules and their functional attributes. We also discuss different types of sensors (biosensors and nanosensors) used in agriculture for detecting pesticides, pathogens and pollutants.

Jasmonates Play an Important Role in Differential Accumulation of Key Oolong Tea Aromas in Two Tea Varieties (Camellia sinensis)

Aroma is an important factor in the measurement of the quality and market value of oolong tea. However, it is hard to develop an oolong tea with good aroma quality using unsuitable tea varieties. To explore the key factors of tea varieties in the formation of oolong tea aromas, the fresh leaves of the Chungui variety (CG, suitable for oolong tea, Camellia sinensis (L.) O. Kuntze) and the Fuyun No. 6 variety (F6, unsuitable for oolong tea, Camellia sinensis (L.) O. Kuntze) were harvested and treated by withering and mechanical stress in order. Then, aroma, transcriptome, and jasmonate (JA) contents, and weighted gene co-expression network analysis (WGCNA), of samples were investigated. The contents of characteristic oolong tea aromas, including indole, (E)-β-ocimene, (E)-nerolidol, α-farnesene, and jasmine lactone, were all accumulated in much higher quantities in the CG variety after withering and mechanical stress. Accordingly, the coding genes of aroma formation synthases TSB2, OCS, NES, AFS, and LOX1, and related genes in MVA, MEP, and ALA pathways, were all much more highly activated. These differential reactions are mainly caused by the higher accumulation of jasmonates, especially methyl jasmonate, a type of important plant signal chemical, in CG after mechanical stress. WGCNA analysis indicated 34 different transcription factors from different families are predicted to be involved in this jasmonate-responsive reaction.

Enhancing plant resistance to biotic stresses through rhizobacteria for sustainable agriculture

Plant Growth-Promoting Rhizobacteria (PGPR) play a crucial role in the enhancement of plant growth. These microorganisms inhabit plant roots and positively influence plant growth through various mechanisms. PGPR facilitate nutrient absorption, combat pathogens, and regulate plant hormone levels. Their impact is achieved through direct actions such as hormone production, enhanced iron uptake via siderophores, phosphate solubilization, and emission of volatile compounds that affect plant signaling and metabolism. In addition, PGPR interactions with rhizosphere microorganisms and the soil indirectly improve plant growth. Numerous biotic stressors affect plant PGPR. The interaction between plants and microorganisms boosts the host resistance to biotic stress. This interaction also regulates the rhizosphere soil by converting organic compounds into plant-absorbable forms, increasing molecule mobilization, and supplying amino acids, carbohydrates, lipids, metabolites, and phytohormones to the host plants. In instances where plants do not secrete lipids, amino acids, carbohydrates, or terpenoids during these interactions, microorganisms contribute these compounds to plants. Investigating these mechanisms, along with changes in gene expression and receptor-mediated signaling in plants, is vital. Utilization of microbial sources as alternatives to conventional agricultural methods is a promising approach. Incorporation of these sources can enhance plant production, quality, growth, and yield.

Structural basis for the regulation of plant transcription factor WRKY33 by the VQ protein SIB1

The WRKY transcription factors play essential roles in a variety of plant signaling pathways associated with biotic and abiotic stress response. The transcriptional activity of many WRKY members are regulated by a class of intrinsically disordered VQ proteins. While it is known that VQ proteins interact with the WRKY DNA-binding domains (DBDs), also termed as the WRKY domains, structural information regarding VQ-WRKY interaction is lacking and the regulation mechanism remains unknown. Herein we report a solution NMR study of the interaction between Arabidopsis WRKY33 and its regulatory VQ protein partner SIB1. We uncover a SIB1 minimal sequence neccessary for forming a stable complex with WRKY33 DBD, which comprises not only the consensus “FxxhVQxhTG” VQ motif but also its preceding region. We demonstrate that the βN-strand and the extended βN-β1 loop of WRKY33 DBD form the SIB1 docking site, and build a structural model of the complex based on the NMR paramagnetic relaxation enhancement and mutagenesis data. Based on this model, we further identify a cluster of positively-charged residues in the N-terminal region of SIB1 to be essential for the formation of a SIB1-WRKY33-DNA ternary complex. These results provide a framework for the mechanism of SIB1-enhanced WRKY33 transcriptional activity.

RNA-Seq Reveals That Multiple Pathways Are Involved in Tuber Expansion in Tiger Nuts (Cyperus esculentus L.).

The tiger nut (Cyperus esculentus L.) is a usable tuber and edible oil plant. The size of the tubers is a key trait that determines the yield and the mechanical harvesting of tiger nut tubers. However, little is known about the anatomical and molecular mechanisms of tuber expansion in tiger nut plants. This study conducted anatomical and comprehensive transcriptomics analyses of tiger nut tubers at the following days after sowing: 40 d (S1); 50 d (S2); 60 d (S3); 70 d (S4); 90 d (S5); and 110 d (S6). The results showed that, at the initiation stage of a tiger nut tuber (S1), the primary thickening meristem (PTM) surrounded the periphery of the stele and was initially responsible for the proliferation of parenchyma cells of the cortex (before S1) and then the stele (S2-S3). The increase in cell size of the parenchyma cells occurred mainly from S1 to S3 in the cortex and from S3 to S4 in the stele. A total of 12,472 differentially expressed genes (DEGs) were expressed to a greater extent in the S1-S3 phase than in S4-S6 phase. DEGs related to tuber expansion were involved in cell wall modification, vesicle transport, cell membrane components, cell division, the regulation of plant hormone levels, signal transduction, and metabolism. DEGs involved in the biosynthesis and the signaling of indole-3-acetic acid (IAA) and jasmonic acid (JA) were expressed highly in S1-S3. The endogenous changes in IAA and JAs during tuber development showed that the highest concentrations were found at S1 and S1-S3, respectively. In addition, several DEGs were related to brassinosteroid (BR) signaling and the G-protein, MAPK, and ubiquitin-proteasome pathways, suggesting that these signaling pathways have roles in the tuber expansion of tiger nut. Finally, we come to the conclusion that the cortex development preceding stele development in tiger nut tubers. The auxin signaling pathway promotes the division of cortical cells, while the jasmonic acid pathway, brassinosteroid signaling, G-protein pathway, MAPK pathway, and ubiquitin protein pathway regulate cell division and the expansion of the tuber cortex and stele. This finding will facilitate searches for genes that influence tuber expansion and the regulatory networks in developing tubers.

Multiple factors influenced the aggregation behavior of adult Eucryptorrhynchus scrobicuatus (Coleoptera: Curculionidae).

Eucryptorrhynchus scrobiculatus (Motschulsky) (Coleoptera: Curculionidae) is a notorious pest of Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae). E. scrobiculatus adults typically aggregate under leaves and in soil crevices at the base of A. altissima in the field. We hypothesize that the environmental factors and conspecific signals determine their aggregation behavior. To test this, we investigated adult numbers in light-exposed and shaded areas of the sample trees and conducted experiments in both field and lab settings. Results revealed that (i) greater adult distribution in shaded areas; (ii) significant influence of temperature and illumination on aggregation tendency in the field; (iii) no gender-based difference in aggregation degree and maximum aggregation between light and dark; (iv) the host plant triggering the aggregation tendency, negatively affected in the absence; (v) the aggregation tendency of E. scrobiculatus weakened with the temperature gradually changing to ordinary temperature; and (vi) mutual attraction and chemical attraction between males and females. Thus, the aggregation behavior was influenced by factors including temperature, light intensity, host plant, and conspecific signals, but light's role was not obvious in the lab.

Casein kinase 1 AELs promote senescence by enhancing ethylene biosynthesis through phosphorylating WRKY22 transcription factor.

Leaf senescence is a complex process regulated by developmental and environmental factors, and plays a pivotal role in the development and life cycle of higher plants. Casein kinase 1 (CK1) is a highly conserved serine/threonine protein kinase in eukaryotes and functions in various cellular processes including cell proliferation, light signaling and hormone effects of plants. However, the biological function of CK1 in plant senescence remains unclear. Through systemic genetic and biochemical studies, we here characterized the function of Arabidopsis EL1-like (AEL), a CK1, in promoting leaf senescence by stimulating ethylene biosynthesis through phosphorylating transcription factor WRKY22. Seedlings lacking or overexpressing AELs presented delayed or accelerated leaf senescence, respectively. AELs interact with and phosphorylate WRKY22 at Thr57, Thr60 and Ser69 residues to enhance whose transactivation activity. Being consistent, increased or suppressed phosphorylation of WRKY22 resulted in the promoted or delayed leaf senescence. WRKY22 directly binds to promoter region and stimulates the transcription of 1-amino-cyclopropane-1-carboxylate synthase 7 gene to promote ethylene level and hence leaf senescence. Our studies demonstrated the crucial role of AEL-mediated phosphorylation in regulating ethylene biosynthesis and promoting leaf senescence by enhancing WRKY22 transactivation activity, which helps to elucidate the fine-controlled ethylene biosynthesis and regulatory network of leaf senescence.

The role of phytomelatonin in plant homeostasis, signaling, and crosstalk in abiotic stress mitigation.

In recent years, there has been an increase in the study of phytomelatonin. Having numerous functions in animals, melatonin produced by plants (phytomelatonin) is also a multi-regulatory molecule with great potential in plant physiology and in mitigating abiotic stresses, such as drought, salinity, chilling, heat, chemical contamination, and UV-radiation stress. This review highlights the primary functions of phytomelatonin as an anti-stress molecule against abiotic stress. We discuss the role of phytomelatonin as a master regulator, oxidative stress manager, reactive oxygen species and reactive nitrogen species regulator, and defense compounds inducer. Although there exist a handful of reviews on the crosstalk of phytomelatonin with other signaling molecules like auxin, cytokinin, gibberellin, abscisic acid, ethylene, nitric oxide, jasmonic acid, and salicylic acid, this review looks at studies that have reported a few aspects of phytomelatonin with newly discovered signaling molecules along with classical signaling molecules with relation to abiotic stress tolerance. The research and applications of phytomelatonin with hydrogen sulfide, strigolactones, brassinosteroids, and polyamines are still in their nascent stage but hold a promising scope for the future. Additionally, this review states the recent developments in the signaling of phytomelatonin with nitrogen metabolism and nitrosative stress in plants.

The VAMP-associated protein VAP27-1 plays a crucial role in plant resistance to ER stress by modulating ER–PM contact architecture in Arabidopsis

The endoplasmic reticulum (ER) and the plasma membrane (PM) form ER–PM contact sites (EPCSs) that allow the ER and PM to exchange materials and information. Stress-induced disruption of protein folding triggers ER stress, and the cell initiates the unfolded protein response (UPR) to resist the stress. However, whether EPCSs play a role in ER stress in plants remains unclear. VESICLE-ASSOCIATED MEMBRANE PROTEIN (VAMP)-ASSOCIATED PROTEIN 27-1 (VAP27-1) functions in EPCS tethering and is encoded by a family of 10 genes (VAP27-1–10) in Arabidopsis thaliana. Here, we used CRISPR-Cas9-mediated genome editing to obtain a homozygous vap27-1 vap27-3 vap27-4 (vap27-1/3/4) triple mutant lacking three of the key VAP27 family members in Arabidopsis. The vap27-1/3/4 mutant exhibits defects in ER–PM connectivity and EPCS architecture, as well as excessive UPR signaling. We further showed that relocation of VAP27-1 to the PM mediates specific VAP27-1-related EPCS remodeling and expansion under ER stress. Moreover, the spatiotemporal dynamics of VAP27-1 at the PM increase ER–PM connectivity and enhance Arabidopsis resistance to ER stress. In addition, we revealed an important role for intracellular calcium homeostasis in the regulation of UPR signaling. Taken together, these results broaden our understanding of the molecular and cellular mechanisms of ER stress and UPR signaling in plants, providing additional clues for improving plant broad-spectrum resistance to different stresses.

Recent advances in research on phosphate starvation signaling in plants

Phosphorus is indispensable for plant growth and development, with its status crucial for determining crop productivity. Plants have evolved various biochemical, morphological, and developmental responses to thrive under conditions of low P availability, as inorganic phosphate (Pi), the primary form of P uptake, is often insoluble in soils. Over the past 25 years, extensive research has focused on understanding these responses, collectively forming the Pi starvation response system. This effort has not only expanded our knowledge of strategies to cope with Pi starvation (PS) but also confirmed their adaptive significance. Moreover, it has identified and characterized numerous components of the intricate regulatory network governing P homeostasis. This review emphasizes recent advances in PS signaling, particularly highlighting the physiological importance of local PS signaling in inhibiting primary root growth and uncovering the role of TORC1 signaling in this process. Additionally, advancements in understanding shoot-root Pi allocation and a novel technique for studying Pi distribution in plants are discussed. Furthermore, emerging data on the regulation of plant-microorganism interactions by the PS regulatory system, crosstalk between the signaling pathways of phosphate starvation, phytohormones and immunity, and recent studies on natural variation in Pi homeostasis are addressed.

Redox active plant phenolic, acetosyringone, for electrogenetic signaling

Redox is a unique, programmable modality capable of bridging communication between biology and electronics. Previous studies have shown that the E. coli redox-responsive OxyRS regulon can be re-wired to accept electrochemically generated hydrogen peroxide (H2O2) as an inducer of gene expression. Here we report that the redox-active phenolic plant signaling molecule acetosyringone (AS) can also induce gene expression from the OxyRS regulon. AS must be oxidized, however, as the reduced state present under normal conditions cannot induce gene expression. Thus, AS serves as a “pro-signaling molecule” that can be activated by its oxidation—in our case by application of oxidizing potential to an electrode. We show that the OxyRS regulon is not induced electrochemically if the imposed electrode potential is in the mid-physiological range. Electronically sliding the applied potential to either oxidative or reductive extremes induces this regulon but through different mechanisms: reduction of O2 to form H2O2 or oxidation of AS. Fundamentally, this work reinforces the emerging concept that redox signaling depends more on molecular activities than molecular structure. From an applications perspective, the creation of an electronically programmed “pro-signal” dramatically expands the toolbox for electronic control of biological responses in microbes, including in complex environments, cell-based materials, and biomanufacturing.

Integration of nitrate and abscisic acid signaling in plants.

To meet the demands of the new Green Revolution and sustainable agriculture, it is important to develop crop varieties with improved yield, nitrogen use efficiency, and stress resistance. Nitrate is the major form of inorganic nitrogen available for plant growth in many well-aerated agricultural soils, and acts as a signaling molecule regulating plant development, growth, and stress responses. Abscisic acid (ABA), an important phytohormone, plays vital roles in integrating extrinsic and intrinsic responses and mediating plant growth and development in response to biotic and abiotic stresses. Therefore, elucidating the interplay between nitrate and ABA can contribute to crop breeding and sustainable agriculture. Here, we review studies that have investigated the interplay between nitrate and ABA in root growth modulation, nitrate and ABA transport processes, seed germination regulation, and drought responses. We also focus on nitrate and ABA interplay in several reported omics analyses with some important nodes in the crosstalk between nitrate and ABA. Through these insights, we proposed some research perspectives that could help to develop crop varieties adapted to a changing environment and to improve crop yield with high nitrogen use efficiency and strong stress resistance.

Heavy metal stress and mitogen activated kinase transcription factors in plants: Exploring heavy metal-ROS influences on plant signalling pathways.

Due to their stationary nature, plants are exposed to a diverse range of biotic and abiotic stresses, of which heavy metal (HM) stress poses one of the most detrimental abiotic stresses, targeting diverse plant processes. HMs instigate the overproduction of reactive oxygen species (ROS), and to mitigate the adverse effects of ROS, plants induce multiple defence mechanisms. Besides the negative implications of overproduction of ROS, these molecules play a multitude of signalling roles in plants, acting as a central player in the complex signalling network of cells. One of the ROS-associated signalling mechanisms is the mitogen-activated protein kinase (MAPK) cascade, a signalling pathway which transduces extracellular stimuli into intracellular responses. Plant MAPKs have been implicated in signalling involved in stress response, phytohormone regulation, and cell cycle cues. However, the influence of various HMs on MAPK activation has not been well documented. In this review, we address and summarise several aspects related to various HM-induced ROS signalling. Additionally, we touch on how these signals activate the MAPK cascade and the downstream transcription factors that influence plant responses to HMs. Moreover, we propose a workflow that could characterise genes associated with MAPKs and their roles during plant HM stress responses.