The target of rapamycin (TOR) is a conserved master regulator of growth1,2 that integrates nutrient availability with developmental programs. While TOR inhibition under nutrient limitation is generally attributed to upstream signaling pathways, endogenous small-molecule regulators of TOR have not been defined in eukaryotes. Here, we show that plants use coumarins to modulate TOR activity. In Arabidopsis thaliana, we discovered that iron deficiency-induced coumarin accumulation represses TOR-S6K signaling and restricts root growth. Structural modeling and kinase activity analyses support a mechanism consistent with competition between the coumarin esculetin and ATP for binding to the catalytic pocket. Together, these findings identify specialized metabolites as modulators of TOR signaling, linking nutrient-responsive metabolism to growth control.

Plant flowering integrates environmental and nutrient cues, yet how mineral nutrients interface with core flowering pathways remains unclear. In this issue of Developmental Cell, Lyu et al. identify a nitrogen-responsive module in which nitrogen availability alters FKF1 physical organization and protein interactions, thereby regulating FT4 stability and controlling flowering time.

Phosphorus (P) is a vital macronutrient, yet its bioavailability in soils is often limited, restricting plant growth. In response to P deficiency, plants adapt by reconfiguring root architecture-impeding primary root growth, promoting lateral root formation, and elongating root hairs-to enhance P acquisition. Central to these responses is the Target of Rapamycin Complex 1 (TORC1), a highly conserved master regulator that integrates nutrient, energy, and environmental signals to balance growth and metabolic demands. Recent studies reveal complex interactions between TORC1 and P homeostasis, highlighting the pivotal role of TORC1 in modulating early root growth. Notably, while early P deficiency impedes root development in an iron (Fe)-independent manner, short-term P deficiency coupled with excess Fe exacerbates this response by inducing oxidative stress, complicating root adaptations. The reciprocal regulation of Fe and P homeostasis, along with the central role of TORC1, sheds new light on the dynamic regulation of root plasticity, particularly lateral root development. This review synthesizes recent advances in TORC1-mediated root architecture under P stress and explores how these interconnected pathways can be harnessed to enhance P use efficiency in crops, offering actionable strategies for sustainable agriculture and crop breeding.

Sulfur (S) is an essential macronutrient for plant growth and resilience. The S-amino acids cysteine (Cys) and methionine (Met) are indispensable for protein synthesis and structural integrity, as well as redox homeostasis and cofactor assembly. Over the past several decades, biochemical and molecular genetic studies demonstrated the core steps in sulfate (SO42-) uptake and assimilation pathways, while it has become increasingly evident that S homeostasis in plants cannot be understood in isolation. Robust and reciprocal regulatory interactions link S with phosphorus (P), nitrogen (N), and iron (Fe). Plants remodel membrane lipid compositions, replacing the phospholipids with sulfolipids under P deficiency. Cys/Met biosynthesis is coordinated with N metabolism. The Fe-S cluster assembly requires a balanced supply of Fe and S. These interactions are orchestrated through shared regulatory circuits and specific hub-regulatory transcription factors, including SULFUR LIMITATION 1 (SLIM1), PHOSPHATE STARVATION RESPONSE 1 (PHR1), NIN-LIKE PROTEIN 7 (NLP7), and FER-LIKE IRON DEFICIENCY-INDUCED FACTOR (FIT). Comparative studies reveal both species-specific and evolutionarily conserved regulatory networks. This review deliberately focuses on mechanistic insights into the regulatory circuits revealed from studies with the model plant Arabidopsis thaliana, where the genetic and molecular resolution enabled detailed dissection of the signaling and regulatory networks. This review also highlights unresolved mechanistic gaps and provides insights into systems-level understanding and potential translational approaches that can be implemented to improve crop nutrient use efficiency and stress resilience.

The transition from vegetative to reproductive growth is a critical phase in the plant life cycle that significantly impacts reproductive success. This complex process is regulated by a dynamic interplay of genetic, molecular, and physiological mechanisms. While the roles of environmental factors such as photoperiod and temperature in flowering regulation are well documented, the impact of nutrient availability - particularly nitrogen and phosphorus - has gained increasing attention. Recent research highlights how these macronutrients intricately interact with key signaling pathways that regulate flowering time. Specifically, while nitrogen deficiency tends to accelerate flowering, phosphate deficiency often results in delayed flowering. This review examines molecular insights into how nitrogen and phosphorus cues influence flowering, offering key strategies for sustainable development.

Genetic variation is generally regarded as a prerequisite for evolution. In principle, epigenetic information inherited independently of DNA sequence can also enable evolution, but whether this occurs in natural populations is unknown. Here we show that single-nucleotide and epigenetic gene body DNA methylation (gbM) polymorphisms explain comparable amounts of expression variance in Arabidopsis thaliana populations. We genetically demonstrate that gbM regulates transcription, and we identify and genetically validate many associations between gbM polymorphism and the variation of complex traits: fitness under heat and drought, flowering time and accumulation of diverse minerals. Epigenome-wide association studies pinpoint trait-relevant genes with greater precision than genetic association analyses, probably due to reduced linkage disequilibrium between gbM variants. Finally, we identify numerous associations between gbM epialleles and diverse environmental conditions in native habitats, suggesting that gbM facilitates adaptation. Overall, our results indicate that epigenetic methylation variation fundamentally shapes phenotypic diversity in a natural population.

Phosphorus (P) deficiency is a critical factor limiting crop productivity, primarily due to its detrimental effects on photosynthesis and dry matter accumulation. In this study, we investigate the role of the rice gene OsPHT2;1 in mediating chloroplast P homeostasis and its subsequent impact on photosynthetic function under low P conditions. Stomatal conductance is typically positively correlated with net photosynthetic rates; however, P deficiency disrupts this relationship, leading to reduced stomatal opening and diminished photosynthetic efficiency. Our findings show that the OsPHT2;1 mutation leads to a decrease in the plastoquinone (PQ) pool size. This change is associated with altered stomatal conductance and modifications in electron transport dynamics, including an increase in the transmembrane proton gradient and a shift from linear to cyclic electron transport. This disruption significantly impairs the transport of photosynthetic products, particularly triose phosphates, essential for sucrose synthesis in the cytoplasm. Additionally, the reduced PQ pool influences the expression of key genes involved in photostability, highlighting the interplay between P homeostasis and photosynthetic regulation. By elucidating the mechanisms underlying OsPHT2;1's role in chloroplast function, our research underscores its significance in optimizing rice adaptation to low P environments, thereby enhancing crop resilience and productivity.

Plant nitrogen nutrition is an essential and energy-costly component of terrestrial food chains. Understanding nitrate sensing in plants can lead to improved crop yields and nutrient use efficiency, directly impacting food security and agricultural sustainability. Herein, we review and present a comprehensive framework for understanding nitrate sensing in plants, integrating molecular, genetic, and physiological aspects. We begin by detailing the primary nitrate response and nitrate starvation response, which are central to the plant's ability to sense and respond to nitrate availability. We then explore the intricate interactions between nitrate signaling and other nutritional pathways such as those for carbon, phosphorus, potassium, and sulfur assimilation and reactive oxygen species (ROS) handling, and how it unfolds in long-distance systemic communication between roots and shoots. Finally, evolutionary insights are provided by comparing nitrate-sensing mechanisms across different plant species as well as Bacteria, Archaea, Chlorophyta, Charophyta (algae), and Fungi, revealing how these mechanisms may have evolved in diverse ecological niches. This review not only provides a framework to project our present and future understanding of plant nitrate and nitrogen nutrition but also offers potential strategies for improving nutrient use efficiency in crops through genetic and biotechnological interventions.

Robust and reproducible plant culture systems are essential for studying physiological, molecular, and developmental responses under controlled conditions. In particular, investigating how plants respond to nutrient limitation or abiotic stress requires precise regulation of the growth environment, something that traditional soil‐ or agar‐based systems often fail to provide. Arabidopsis thaliana , the leading model plant species, presents unique challenges in this regard due to its compact size and sensitivity to environmental variability. To address these limitations, hydroponic systems have emerged as powerful tools, enabling accurate control of nutrient availability and direct access to root and shoot tissues. Here, we present a cost‐effective, scalable hydroponic culture system for Arabidopsis , constructed entirely from widely available laboratory materials, such as 8‐strip PCR tubes and 96‐well pipette tip boxes. This system minimizes contamination risks, supports long‐term cultivation, and allows for high‐throughput phenotyping, tissue sampling, and downstream molecular analyses. The design facilitates reproducible experiments under nutrient‐limiting or stress‐inducing conditions. Step‐by‐step set up and maintenance instructions are provided, offering researchers a reliable platform for dissecting nutrient signaling pathways and environmental stress responses in Arabidopsis and similarly sized plant species. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol : Setting up the hydroponic culture system Support Protocol : Advantages of split‐root hydroponic systems for investigating local and systemic nutrient signaling

The transition from vegetative to reproductive growth is vital for plant fitness and crop yield and is strongly influenced by nutrient availability. While nitrogen deficiency accelerates flowering, phosphorus (P) limitation delays it. However, the molecular basis for how P availability regulates flowering time remains unclear. Here, through genome-wide association mapping in Arabidopsis, we uncover genetic variation in β-GLUCOSIDASE 25 (bGLU25) that modulates flowering under P-limited conditions. In P-sufficient environments, bGLU25 localizes to the endoplasmic reticulum. Under P limitation, however, bGLU25 translocates to the cytosol, a process mediated by P-regulated SERINE CARBOXY PEPTIDASE 50 (SCP50). In the cytosol, bGLU25 binds to JACALIN-LECTIN LIKE1 (AtJAC1), preventing the nuclear translocation of the Flowering Locus C (FLC) regulator GLYCINE-RICH RNA-BINDING PROTEIN 7 (GRP7). This cytosolic sequestration of GRP7 under P-deprivation elevates FLC expression, delaying flowering. Moreover, in the monocot rice, the homologs of bGLU25 also modulate flowering responses to P availability, indicating a conserved role for bGLU25 across flowering plants. Our findings provide a molecular framework for breeding strategies aimed at optimizing flowering time in response to P levels. ### Competing Interest Statement The authors have declared no competing interest.

The transition from vegetative to reproductive growth is vital for plant fitness and crop yield and is strongly influenced by nutrient availability. While nitrogen deficiency accelerates flowering, phosphorus (P) limitation delays it. However, the molecular basis for how P availability regulates flowering time remains unclear. Here, through genome-wide association mapping in Arabidopsis, we uncover genetic variation in β-GLUCOSIDASE 25 (bGLU25) that modulates flowering under P-limited conditions. In P-sufficient environments, bGLU25 localizes to the endoplasmic reticulum. Under P limitation, however, bGLU25 translocates to the cytosol, a process mediated by P-regulated SERINE CARBOXY PEPTIDASE-Like 50 (SCPL50). In the cytosol, bGLU25 binds to JACALIN-LECTIN LIKE1 (AtJAC1), preventing the nuclear translocation of the Flowering Locus C (FLC) regulator GLYCINE-RICH RNA-BINDING PROTEIN 7 (GRP7). Cytosolic sequestration of GRP7 during P deprivation elevates FLC expression, contributing to delayed flowering. Our findings provide a molecular framework for breeding strategies to optimize flowering time in response to P levels.

The accelerated pace of climate change over the past several years should serve as a wake-up call for all scientists, farmers, and decision makers, as it severely threatens our food supply and could result in famine, migration, war, and an overall destabilization of our society. Rapid and significant changes are therefore needed in the way we conduct research on plant resilience, develop new crop varieties, and cultivate those crops in our agricultural systems. Here, we describe the main bottlenecks for these processes and outline a set of key recommendations on how to accelerate research in this critical area for our society.

Nutrient availability profoundly influences plant root system architecture, which critically determines crop productivity. While Arabidopsis has provided important insights into the genetic responses to nutrient deficiency, translating this knowledge to crops, particularly wheat, remains a subject of inquiry. Here, examining a diverse wheat population under varying nitrogen (N), phosphorus (P), potassium (K), and iron (Fe) levels, we uncover a spectrum of root responses, spanning from growth inhibition to stimulation, highlighting genotype-specific strategies. Furthermore, we reveal a nuanced interplay between macronutrient deficiency (N, P, and K) and Fe availability, emphasizing the central role of Fe in modulating root architecture. Through genome-wide association mapping, we identify 11 quantitative trait loci underlying root traits under varying nutrient availabilities, including homologous genes previously validated in Arabidopsis, supporting our findings. In addition, utilizing transcriptomics, reactive oxygen species (ROS) imaging, and antioxidant treatment, we uncover that wheat root growth inhibition by nutrient deficiency is attributed to ROS accumulation, akin to the role of ROS in governing Arabidopsis root responses to nutrient deficiency. Therefore, our study reveals the conservation of molecular and physiological mechanisms between Arabidopsis and wheat to adjust root growth to nutrient availability, paving the way for targeted crop improvement strategies aimed at increasing nutrient use efficiency.

Copper (Cu) is a crucial micronutrient essential for the growth and development of plants. Rice exhibits remarkable resistance to Cu deficiency, but the underlying molecular mechanisms are not well understood. In this study, we reveal that the plant's ability to withstand Cu deficiency is orchestrated by a transcription factor known as OsSPL9. We have demonstrated that OsSPL9 functions as a central regulator of Cu homeostasis. Disrupting OsSPL9 through knockout significantly reduced the plant's tolerance to Cu deficiency. As a result, the spl9 mutants exhibited reduced Cu accumulation in their shoots when compared with wild-type plants. This reduction was linked to a disruption in the transport of Cu from older leaves to younger ones. Furthermore, we show that OsSPL9 directly bound to GTAC motifs in the promoters of key genes involved in Cu uptake and transport, as well as Cu-miRNAs, and enhanced their transcription under Cu-deficient conditions. Overall, our findings shed light on the molecular basis of rice resilience to Cu deficiency stress and place the transcription factor OsSPL9 as a master regulator of this response. The transcription factor OsSPL9 serves as a central regulator of copper homeostasis in rice and endows rice with resilience to copper deficiency.

In nature, or under field conditions, plants and crops are routinely subjected to a combination of different abiotic and/or biotic stress conditions that may affect them simultaneously or sequentially (e.g., drought and heat, flooding and heat, nutrient deficiency and drought, flood followed by salinity stress, and many other stress combinations that include pathogens, increasing levels of CO2, and other stress factors; Figure 1). Past climatic events and ongoing research have taught us that different stress combinations can have a dramatic and devastating impact on wild and cultivated plants, as well as on different ecosystems and their associated microbiomes. Notable examples are the drought and heat wave episodes that occurred during the summers of 1980 and 1988 in the US and resulted in yield losses estimated at 39 and 53 billion dollars to agriculture, respectively (https://www.ncei.noaa.gov/access/billions/events). As the frequency and intensity of many abiotic and/or biotic stresses, and their combinations, are gradually increasing due to global warming and climate change (https://climate.nasa.gov/extreme-weather/), a deeper understanding of the molecular mechanisms, physiological responses, and overall ecological processes involved in plant responses and acclimation to stress combinations is needed. With the overall goal of increasing the awareness of the plant research community to this emerging challenge, we organized this Special Issue focused on "Stress combination: From genes to ecosystems." The special issue comprises five research papers, two resource papers, and nine reviews. In the first research paper, Balfagon et al. (2024) reported on the transcription factor WRKY48 which functions as a key suppressor of plant responses specific to a combination of high light and heat stress. The authors further showed that WRKY48 expression is attenuated by jasmonic acid (JA) during the stress combination and identified putative genes that function downstream to WRKY48. This paper is significant as it is likely the first to identify a transcription factor that has a function specific to a set of two different stresses combined. Another research paper is that of Li et al. (2024) who studied the synergistic regulation at morphological, physiological, transcriptional, and metabolic levels of different tomato genotypes subjected to a combination of heat and salinity. These authors further identified the oxidative phosphorylation pathway and alternative oxidase 1 as potentially playing a key role in this stress combination. In the third research paper of the special issue, Ludwig et al. (2024) studied phenotypic variation in the response of 149 accessions of Brachypodium to heat, drought, and drought combined with heat. Using GWAS and SNP analyses the authors identified different loci associated with plant responses to stress combination, revealing that these responses are not simply the additive effects of drought and heat, as they differ qualitatively from the responses to drought or heat alone. In the fourth research paper, Koch et al. (2024) studied the interactions between heat stress and excess nitrogen fertilization in potato. Using transgenic potato plants, they showed that yield reduction caused by elevated temperatures and high nitrogen fertilization can be mitigated by overexpression of SELF-PRUNING 6A (SP6A), a homolog of FLOWERING LOCUS T, that functions as a tuberigen in potato. This is a significant finding as it proposes a new avenue in mitigating nutrient and heat stress combination in potato. In the fifth research paper, DeLoose, Cho, et al. (2024) also focused on nutrient stress combination, however, with a focus on iron and phosphate stress interactions in Arabidopsis. Using a GWAS analysis the authors of this exciting research paper determined that PDR9 allelic variation and MYB63 function modulate nutrient-dependent coumarin homeostasis in Arabidopsis to regulate the interactions between iron and phosphate. The two resource papers featured in the special issue include the paper by Peláez-Vico et al. (2024) that subjected soybean plants to a multifactorial stress combination (MFSC) of up to five different stresses (water deficit, salinity, low phosphate, acidity, and cadmium), in an increasing level of complexity and conducted an integrative transcriptomic-phenotypic analysis of their reproductive and vegetative tissues. This paper is highly important as it provides significant datasets for vegetative and reproductive tissues of a crop plant subjected to stress combination. In the second resource paper, Pardo-Hernández et al. (2024) provide important datasets for wild type and abscisic acid (ABA) deficient tomato plants subjected to a combination of heat and salinity stress, offering new insights into the ABA-dependent and ABA-independent responses of tomato to stress combination. The nine different reviews included in the special issue address multiple aspects of plant, crop, and ecosystem responses to stress combination. In their review, DeLoose, Clúa, et al. (2024) discuss the response of plants to nutrient stress combinations with a focus on the regulation of phosphorous homeostasis in plants. The authors discuss deficiencies in phosphorous combined with other essential elements, such as nitrogen, iron, and zinc, as well as with non-essential elements such as aluminum and sodium. Rillig et al. (2024) describe in their review a new classification scheme that captures the different targets of global change factors along the ecological hierarchy. The authors discuss how effects can propagate across the levels of the ecological hierarchy, upwards and downwards, presenting new opportunities for explaining the non-additivity of effects of multiple factors. The conceptual framework described by these authors will help inform the next generation of plant-focused global change experiments, specifically aimed at the non-additivity of effects at the confluence of many factors. Sadras et al. (2024) review some of the very interesting aspects of virus-virus (inter-virus) and virus-drought combinations, discussing antagonistic, additive, and synergistic inter-virus relationships in double infections, as well as additive or antagonistic virus-drought interactions. They then relate these to crop yield in agriculture and crop fitness in the field. Zandalinas et al. (2024) tackle the challenging subject of MFSC. The authors explain how climate change, industrial pollution, and global warming elevate the frequency, complexity, and intensity of multiple stress combinations, and discuss the impacts of MFSC on agriculture, microbiomes, and ecosystems worldwide. Chen et al. (2024) discuss in their review the combination of drought and salinity stresses. The authors address the challenges this stress combination poses to agriculture and compare some of the key traits that differentiate between xerophytes (naturally drought-tolerant plants) and mesophytes (majority of the crops). Finally, the authors propose ways of incorporating some of these traits into breeding practices to produce more drought- and salt-resistant crops. In their review, Renziehausen et al. (2024) address the highly important combination of flooding or waterlogging stress with other abiotic stresses such as heat stress. The authors discuss how flooding/anoxia signaling pathways are affected by other stresses and propose molecular mechanisms that could play a key role in stress combinations that include hypoxia and other stresses. Cagnola et al. (2024) analyzed the impact of combined abiotic stresses, such as water restriction and nitrogen deficiency, or water restriction and elevated temperatures, on crop yield per unit soil area in corn. They further address the highly important aspect of plant population density, which generates crowding stress during stress combination, and show that depending on different factors, the magnitude of the detrimental effects of two combined stresses on field-grown plants can be lower, similar, or higher than the sum of the individual stresses. In their review, Sato et al. (2024) provide a comprehensive overview of how drought, heat, and the combination of these stress conditions affect plants and crops by altering factors such as stomatal conductance, photosynthetic activity, cellular oxidative conditions, metabolomic profiles, and molecular signaling mechanisms. The authors further focus on stress-response regulatory factors such as transcription factors and other signaling components that play a key role during stress combination. Finally, Han et al. (2024) discuss in their review how plants coordinately respond to a combination of shade and environmental stresses such as drought, soil salinity, extreme temperatures, pathogens, and pests. They present these interactions with a focus on the shade avoidance syndrome, and the role of phytochrome B and the transcription factors PHYTOCHROME INTERACTING FACTORs (PIFs) in these responses. We hope that the wide array of research, resource, and review articles on stress combination, included in this special issue, will spark interest in young scientists, highlight this important subject to the broad scientific community, and attract the attention of policy and decision makers. The timing of this special issue, approximately 20 years following the first molecular and physiological analyses of stress combination in plants (Mittler, 2006; Rizhsky et al., 2002, 2004), the over 1000 papers published on stress combination since, and the 2023 report on climate change by IPCC (Lee & Romero, 2023; https://www.ipcc.ch/report/ar6/syr/), further highlights the importance of this subject, and its relevance to current events and the rapid changes in our climate and environment. As the impacts of global warming, climate change, and industrial/urban pollution, on plants and crops continue to grow on a yearly basis (e.g., Zandalinas et al., 2021, 2024), so will the importance of studying stress combination/MFSC. To truly develop Climate-, pathogen- and/or pollution-resilient crops, we must understand how plants and crops respond to and acclimate to stress combination.

The Target of Rapamycin Complex 1 (TORC1) is a crucial eukaryotic kinase that modulates growth in response to nutrient availability. Phosphorus (P) is an essential macronutrient, and its deficiency induces extensive reprogramming of growth and defense strategies in plants. This process involves Phosphate Starvation Response 1 (PHR1), a master regulator of the Phosphate Starvation Response (PSR). In this study, we identify a novel, non-canonical role for TORC1 in regulating P starvation responses in Arabidopsis. We demonstrate that P limitation activates TORC1, leading to the stabilization of PHR1. Inhibition of TORC1 increased sensitivity to P starvation, accompanied by disruption of starvation-induced transcriptional reprogramming. Additionally, our results reveal that the TORC1-PHR1 signaling axis plays a crucial role in reprogramming the expression of genes involved in the plant immune signaling network. This regulation is critical for the symbiotic association with the endophytic fungus Piriformospora indica under P starvation. These findings underscore the significant role of the TORC1-PHR1 module in orchestrating the PSR and highlight the evolutionary adaptation of TORC1 signaling pathways in plants. ### Competing Interest Statement The authors have declared no competing interest.

Zinc (Zn) deficiency is the most prevalent micronutrient disorder in rice and leads to delayed development and decreased yield. Nevertheless, despite its primary importance, how rice responds to Zn deficiency remains poorly understood. This study presents genetic evidence supporting the crucial role of OsbZIP48 in regulating rice's response to Zn deficiency, consistent with earlier findings in the model plant Arabidopsis. Genetic inactivation of OsbZIP48 in rice seedlings resulted in heightened sensitivity to Zn deficiency and reduced Zn translocation from roots to shoots. Consistently, OsbZIP48 was constitutively expressed in roots, slightly induced by Zn deficiency in shoots and localized into nuclei induced by Zn deficiency. Comparative transcriptome analysis of the wild-type plants and osbzip48 mutant grown under Zn deficiency enabled the identification of OsbZIP48 target genes, including key Zn transporter genes (OsZIP4 and OsZIP8). We demonstrated that OsbZIP48 controlled the expressions of these genes by directly binding to their promoters, specifically to the Zn deficiency response element motif. This study establishes OsbZIP48 as a critical transcription factor in rice's response to Zn deficiency, offering valuable insights for developing Zn-biofortified rice varieties to combat global Zn limitation.

Global warming will lead to significantly increased temperatures on earth. Plants respond to high ambient temperature with altered developmental and growth programs, termed thermomorphogenesis. Here we show that thermomorphogenesis is conserved in Arabidopsis, soybean, and rice and that it is linked to a decrease in the levels of the two macronutrients nitrogen and phosphorus. We also find that low external levels of these nutrients abolish root growth responses to high ambient temperature. We show that in Arabidopsis, this suppression is due to the function of the transcription factor ELONGATED HYPOCOTYL 5 (HY5) and its transcriptional regulation of the transceptor NITRATE TRANSPORTER 1.1 (NRT1.1). Soybean and Rice homologs of these genes are expressed consistently with a conserved role in regulating temperature responses in a nitrogen and phosphorus level dependent manner. Overall, our data show that root thermomorphogenesis is a conserved feature in species of the two major groups of angiosperms, monocots and dicots, that it leads to a reduction of nutrient levels in the plant, and that it is dependent on environmental nitrogen and phosphorus supply, a regulatory process mediated by the HY5-NRT1.1 module.

SUMMARY Plant roots release phytochemicals into the soil environment to influence nutrient availability and uptake. Arabidopsis thaliana roots release phenylpropanoid coumarins in response to iron (Fe) deficiency, likely to enhance Fe uptake and improve plant health. This response requires sufficient phosphorus (P) in the root environment. Nonetheless, the regulatory interplay influencing coumarin production under varying availabilities of Fe and P is not known. Through genome‐wide association studies, we have pinpointed the influence of the ABC transporter G family member, PDR9, on coumarin accumulation and trafficking (homeostasis) under combined Fe and P deficiency. We show that genetic variation in the promoter of PDR9 regulates its expression in a manner associated with coumarin production. Furthermore, we find that MYB63 transcription factor controls dedicated coumarin production by regulating both COUMARIN SYNTHASE ( COSY ) and FERULOYL‐CoA 6′‐HYDROXYLASE 1 ( F6′H1 ) expression while orchestrating secretion through PDR9 genes under Fe and P combined deficiency. This integrated approach illuminates the intricate connections between nutrient signaling pathways in coumarin response mechanisms.

The rising interest in foliar nutrient spraying as a strategy to boost crop yields has led to investigations of how such application influences nutrient uptake and accumulation, especially in edible plant parts. Despite its importance, the effects of single versus simultaneous nutrient application on plant absorption, transport, and accumulation have been underexplored. This study addresses this knowledge gap by examining the physiological and molecular responses of rice to foliar application of nitrogen (N) and zinc (Zn) individually and in combination at different growth stages. We assessed how the treatments affect rice grain yield and nutrient accumulation in relation to the expression of Zn transport-related genes. Foliar application of N+Zn+ at the tillering stage resulted in a 62.01% increase in grain yield compared to the control. Additionally, Zn concentrations in brown rice were increased by 26.04% and 34.20% when N0Zn+ and N+Zn+ treatments, respectively, were applied at panicle initiation. Gene expression analysis revealed that the timing and nutrient combination significantly influenced rice productivity and grain Zn concentration. At the tillering stage, the N+Zn+ treatment elevated the expression of Zn transporters such as OsZIP3, OsZIP4, and OsZIP9 in leaves, thereby enhancing grain yield. At panicle initiation, the nutrient treatments influenced a broad range of genes, including OsZIP4, OsZIP9, OsHAM2, OsDUR3, OsAAP1, OsGS1;1, and OsFd-GOGAT, affecting grain Zn and N accumulation. These insights are crucial for developing targeted nutrient management strategies to optimize rice yield and grain nutritional quality for the benefit of consumers.