Use of nanomaterials (NMs) to improve plant abiotic stress tolerance (AST) is a hot topic in NM-enabled agriculture. Previous studies mainly focused on the physiological and biochemical responses of plants treated with NMs under abiotic stress. To use NMs for improving plant AST, it is necessary to understand how they act on this tolerance at the omics and epigenetics levels. In this review, we summarized the knowledge of NM-improved abiotic stress tolerance in relation to omics (such as metabolic, transcriptomic, proteomic, and microRNA), DNA methylation, and histone modifications. Overall, NMs can improve plant abiotic stress tolerance through the modulation at omics and epigenetics levels.

Plants are exposed to adverse environmental conditions, including cold, drought, heat, salinity, and heavy metals, which negatively impact plant growth and productivity of edible crops worldwide. Although the previous literature summarized the nanoparticle’s involvement in abiotic stress mitigation, the interaction of nanoparticles with other stress mitigators to overcome abiotic stress from plants remains unclear. Currently, nanotechnology is considered a growing new field in agriculture for understanding plants’ adapted stress tolerance mechanisms. Recent research has shown that nanoparticles can effectively mitigate abiotic stress by interacting synergistically with plant growth regulators. To address this, we comprehensively demonstrated the combined positive potential of nanoparticles in combination with plant growth regulators (signaling molecules, phytohormones, nanoparticles-nanoparticles interaction, fungi, plant growth promoting rhizobacteria and other metal salts) to improve plant growth and mitigate abiotic stresses. Their co-applications augment the plant’s growth, nutrient uptake, antioxidant defense system, water absorption, cell viability, water use efficiency, and photosynthetic and biochemical attributes by reducing oxidative stressors under various abiotic stresses in different plant species. This review provides a comprehensive overview of the combined applications of nanoparticles and plant growth regulators, a novel strategy to reduce the harmful effects of abiotic stress on plants. It identifies research gaps and recommends future studies to overcome their phytotoxicity worldwide.

The growing global population presents a significant challenge to ensuring food security, further compounded by the increasing threat of salinity to agricultural productivity. Wheat, a major staple food providing 20% of the total caloric intake for humans, is susceptible to salinity stress. Developing new salt-tolerant wheat cultivars using wheat breeding techniques and genetic modifications is crucial to addressing this issue while ensuring the sustainability and efficiency of wheat production systems within the prevailing climate trend. This review overviews the current landscape in this field and explores key mechanisms and associated genetic traits that warrant attention within breeding programs. We contend that traditional approaches to breeding wheat for Na⁺ exclusion have limited applicability across varying soil salinity levels, rendering them inefficient. Moreover, we question current phenotyping approaches, advocating for a shift from whole-plant assessments to cell-based phenotyping platforms. Finally, we propose a broader use of wild wheat relatives and various breeding strategies to tap into their germplasm pool for inclusion in wheat breeding programs.

Salinity stress is a major environmental stress affecting crop productivity, and its negative impact on global food security is only going to increase, due to current climate trends. Salinity tolerance was present in wild crop relatives but significantly weakened during domestication. Regaining it back requires a good understanding of molecular mechanisms and traits involved in control of plant ionic and ROS homeostasis. This review summarizes our current knowledge on the role of major plant hormones (auxin, cytokinins, abscisic acid, salicylic acid, and jasmonate) in plants adaptation to soil salinity. We firstly discuss the role of hormones in controlling root tropisms, root growth and architecture (primary root elongation, meristematic activity, lateral root development, and root hairs formation). Hormone-mediated control of uptake and sequestration of key inorganic ions (sodium, potassium, and calcium) is then discussed followed by regulation of cell redox balance and ROS signaling in salt-stressed roots. Finally, the role of epigenetic alterations such as DNA methylation and histone modifications in control of plant ion and ROS homeostasis and signaling is discussed. This data may help develop novel strategies for breeding and cultivating salt-tolerant crops and improving agricultural productivity in saline regions.

Plant calmodulins (CaMs) and calmodulin-like proteins (CMLs) mediate Ca²⁺ signaling in response to abiotic stresses. Manipulation of this signaling in crops could increase stress tolerance. We review methods for detecting Ca²⁺ signals, regulatory roles of CaMs and CMLs, binding targets, and Ca²⁺ networks under abiotic stress in organelles.

Soil salinity is a big environmental issue affecting crop production. Although seed nanopriming has been widely used to improve seed germination and seedling growth under salinity, our knowledge about the underlying mechanisms is still insufficient. Herein, we newly synthesized selenium-doped carbon dots nanoparticles coated with poly acrylic acid (poly acrylic acid coated selenium doped carbon dots, PAA@Se-CDs) and used it to prime seeds of rapeseeds. The TEM (transmission electron microscope) size and zeta potential of PAA@Se-CDs are 3.8 ± 0.2 nm and −30 mV, respectively. After 8 h priming, the PAA@Se-CDs nanoparticles were detected in the seed compartments (seed coat, cotyledon, and radicle), while no such signals were detected in the NNP (no nanoparticle control) group (SeO₂ was used as the NNP). Nanopriming with PAA@Se-CDs nanoparticles increased rapeseeds germination (20%) and seedling fresh weight (161%) under saline conditions compared to NNP control. PAA@Se-CDs nanopriming significantly enhanced endo-β-mannanase activities (255% increase, 21.55 µmol h⁻¹ g⁻¹ vs. 6.06 µmol h⁻¹ g⁻¹, at DAS 1 (DAS, days after sowing)), total soluble sugar (33.63 mg g⁻¹ FW (fresh weight) vs. 20.23 mg g⁻¹ FW) and protein contents (1.96 µg g⁻¹ FW vs. 1.0 µg g⁻¹ FW) to support the growth of germinating seedlings of rapeseeds under salt stress, in comparison with NNP control. The respiration rate and ATP content were increased by 76% and 607%, respectively. The oxidative damage of salinity due to the over-accumulation of reactive oxygen species (ROS) was alleviated by PAA@Se-CDs nanopriming by increasing the antioxidant enzyme activities (SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase)). Another mechanism behind PAA@Se-CDs nanopriming improving rapeseeds salt tolerance at seedling stage was reducing sodium (Na⁺) accumulation and improving potassium (K⁺) retention, hence increasing the K⁺/Na⁺ ratio under saline conditions. Overall, our results not only showed that seed nanopriming with PAA@Se-CDs could be a good approach to improve salt tolerance, but also add more knowledge to the mechanism behind nanopriming-improved plant salt tolerance at germination and early seedling growth stage.

Salt stress severely affects plant growth and yield. The transcription factor NAC plays a variety of important roles in plant abiotic stress, but we know relatively little about the specific molecular mechanisms of NAC in antioxidant defense. Here, our genetic studies reveal the positive regulation of salt tolerance in maize by the transcription factor ZmNAC84. Under salt stress, overexpression of ZmNAC84 in maize increased the expression of ZmCAT1, enhanced CAT activity, and consequently reduced H₂O₂ accumulation, thereby improving salt stress tolerance in maize. Whereas RNA interference-mediated knockdown of ZmNAC84 produced the opposite effect. Subsequently, we found that ZmNAC84 directly binds to and regulates the expression of the ZmCAT1 promoter, and the hybridized material also demonstrated that ZmCAT1 is a downstream target gene of ZmNAC84. In addition, phenotypic and biochemical analyses indicated that ZmCAT1 positively regulated salt tolerance by regulating H₂O₂ accumulation under salt stress. Taken together, these results reveal the function of ZmNAC84 in regulating ZmCAT1-mediated antioxidant defense in response to salt stress in plants.

Soil salinity is a worldwide issue and a major threat to global food security. Salinity tolerance is a complex mechanism that is conferred by numerous molecular, physiological, and biochemical traits. Of critical importance are plant’s ability to regulate redox balance without compromising reactive oxygen species (ROS) signalling and maintain cytosolic ion homeostasis. In this study, the mechanistic basis of K⁺ retention ability in leaf mesophyll (an important but highly sensitive plant tissue) was compared between halophytic quinoa and glycophytic spinach. Phenotypic data showed quinoa outperformed spinach under 100 to 500 mmol L⁻¹ NaCl salinity. The major difference behind this differential salinity sensitivity was a differential K⁺ uptake in leaf mesophyll. Electrophysiological and molecular experiments revealed that a superior ability of mesophyll K⁺ retention in quinoa was conferred by three complementary mechanisms: (i) an intrinsically lower H⁺-ATPase activity in quinoa (potentially as an energy saving strategy); (ii) reduced sensitivity of K⁺ transporters to ROS; and (iii) increased sensitivity of ROS-inducible Ca²⁺-permeable channels. Moreover, the sensitivity of K⁺-transport systems to ROS was further examined in NaCl-acclimated quinoa and spinach plants. The key factors differentiating between K⁺ retention in acclimated leaf mesophyll was associated with the reduced sensitivity and gene expression of K⁺-permeable outward rectifying channel (GORK), Arabidopsis potassium transporter 1 (AKT1), and high affinity potassium transporter 5 (HAK5) to additional NaCl and ROS stress, along with the upregulation of ROS scavenging system. Taken together, our results showed that the tissue-specific and ROS-specific regulation of K⁺ retention are important for conferring salinity tolerant at least in the halophyte quinoa.

Shanlan upland rice is an important landrace resource with high drought stress (DS) tolerance. Despite its importance, genes responsible for yield in Shanlan upland rice have yet to be discovered. Our previous study identified a drought-responsive zinc finger protein, ZOS7, as highly expressed in Shanlandao upland rice. However, the function of this gene in controlling drought tolerance remains largely unexplored. In this study, we found that overexpressing ZOS7, a drought-responsive zinc finger protein, in rice increased biomass and yield under drought stress. Co-overexpressing ZOS7 and MYB60, encoding a protein with which ZOS7 interacted, intensified the yield increase. ZOS7 and MYB60 appear to form a module that confers drought tolerance by regulating stomatal density and wax biosynthesis. The ZOS7-MYB60 module could be used in molecular breeding for drought tolerance in rice.

The rapid elongation of rice (Oryza sativa) coleoptile is pivotal for the plant plumule to evade hypoxia stress induced by submergence, a condition often arising from overirrigation, ponding, rainstorms, or flooding. While brassinosteroids (BRs) are recognized for their diverse roles in plant growth and development, their influence on coleoptile elongation under hypoxic conditions remains largely unexplored. In this study, we demonstrate the significant requirement of BRs for coleoptile elongation in deep water. During coleoptile development, Glycogen Synthase Kinase3-Like Kinase2 (GSK2), the central inhibitor of BR signaling in rice, undergoes substantial suppression in deep water but induction in air. In contrast, the dephosphorylated form of BRASSINAZOLE RESISTANT1 (OsBZR1), representing the active form of the key BR signaling transcription factor, is induced in water but suppressed in air. Remarkably, the knockout of GSK3-like kinase genes significantly enhances coleoptile elongation in deep water, strongly indicating a vital contribution of BR response to hypoxia-stimulated coleoptile elongation. Transcriptome analysis uncovers both BR-associated and BR-independent hypoxia responses, implicating substance metabolism, redox reactions, abiotic stress responses, and crosstalk with other hormones in the regulation of BR-induced hypoxia responses. In summary, our findings suggest that rice plumules rapidly elongate coleoptiles through the activation of BR response in deep water, enabling them to escape from submergence-induced hypoxia stress.

Leaf senescence is an orderly and highly coordinated process, and finely regulated by ethylene and nitrogen (N), ultimately affecting grain yield and nitrogen-use efficiency (NUE). However, the underlying regulatory mechanisms on the crosstalk between ethylene- and N-regulated leaf senescence remain a mystery in maize. In this study, ethylene biosynthesis gene ZmACS7 overexpressing (OE-ZmACS7) plants were used to study the role of ethylene regulating leaf senescence in response to N deficiency, and they exhibited the premature leaf senescence accompanied by increased ethylene release, decreased chlorophyll content and F_v/F_m ratio, and accelerated chloroplast degradation. Then, we investigated the dynamics changes of transcriptome reprogramming underlying ethylene-accelerated leaf senescence in response to N deficiency. The differentially expressed genes (DEGs) involved in chlorophyll biosynthesis were significantly down-regulated, while DEGs involved in chlorophyll degradation and autophagy processes were significantly up-regulated, especially in OE-ZmACS7 plants in response to N deficiency. A gene regulatory network (GRN) was predicted during ethylene-accelerated leaf senescence in response to N deficiency. Three transcription factors (TFs) ZmHSF4, ZmbHLH106, and ZmEREB147 were identified as the key regulatory genes, which targeted chlorophyll biosynthesis gene ZmLES22, chlorophyll degradation gene ZmNYC1, and autophagy-related gene ZmATG5, respectively. Furthermore, ethylene signaling key genes might be located upstream of these TFs, generating the signaling cascade networks during ethylene-accelerated leaf senescence in response to N deficiency. Collectively, these findings improve our molecular knowledge of ethylene-accelerated maize leaf senescence in response to N deficiency, which is promising to improve NUE by manipulating the progress of leaf senescence in maize.

In grain crops such as maize (Zea mays), leaf angle (LA) is a key agronomic trait affecting light interception and thus planting density and yield. Nitrogen (N) affects LA in plants, but we lack a good understanding of how N regulates LA. Here, we report that N deficiency enhanced lignin deposition in the ligular region of maize seedlings. In situ hybridization showed that the bZIP transcription factor gene ZmbZIP27 is mainly expressed in the phloem of maize vascular bundles. Under N-sufficient conditions, transgenic maize overexpressing ZmbZIP27 showed significantly smaller LA compared with wild type (WT). By contrast, zmbzip27_ems mutant showed larger LA under both N-deficient and N-sufficient conditions compared with WT. Overexpression of ZmbZIP27 enhanced lignin deposition in the ligular region of maize in the field. We further demonstrated that ZmbZIP27 could directly bind the promoters of the microRNA genes ZmMIR528a and ZmMIR528b and negatively regulate the expression levels of ZmmiR528. ZmmiR528 knockdown transgenic maize displayed erect architecture in the field by increasing lignin content in the ligular region of maize. Taken together, these results indicate that ZmbZIP27 regulates N-mediated LA size by regulating the expression of ZmmiR528 and modulating lignin deposition in maize.

Phosphorus is a limiting factor in agriculture due to restricted availability in soil and low utilization efficiency of crops. The identification of superior haplotypes of key genes responsible for low-phosphate (Pi) tolerance and their natural variation is important for molecular breeding. In this study, we conducted genome-wide association studies on low-phosphate tolerance coefficients using 152 maize inbred lines, and identified a significant association between SNPs on chromosome 7 and a low-phosphate tolerance coefficient. ZmGRF10 was identified as a candidate gene involved in adaptation of maize to Pi starvation. Expression of ZmGRF10 is induced by Pi starvation. A mutation in ZmGRF10 alleviated Pi starvation stress. RNA-seq analyses revealed significant upregulation of genes encoding various phosphatases in the zmgrf10-1 mutant, suggesting that ZmGRF10 negatively regulates expression of these genes, thereby affecting low-Pi tolerance by suppressing phosphorus remobilization. A superior haplotype with variations in the promoter region exhibited lower transcription activity of ZmGRF10. Our study unveiled a novel gene contributing to tolerance to low-Pi availability with potential to benefit molecular breeding for high Pi utilization.

Regulation of iron homeostasis in maize remains unclear, despite the known roles of FER-Like Fe deficiency-induced transcription factor (FIT) in Arabidopsis and rice. ZmFIT, like AtFIT and OsFIT, interacts with iron-related transcription factors 2 (ZmIRO2). Here, we investigate the involvement of ZmFIT in iron homeostasis. Mutant ZmFIT lines exhibiting symptoms of Fe deficiency had reduced shoot iron content. Transcriptome analysis revealed downregulation of Fe deficiency-responsive genes in the roots of a Zmfit mutant. ZmFIT facilitates the nuclear translocation of ZmIRO2 to activate transcription of downstream genes under Fe-deficient conditions. Our findings suggest that ZmFIT, by interaction with ZmIRO2, mediates iron homeostasis in maize. Notably, the binding and activation mechanisms of ZmFIT resemble those in Arabidopsis but differ from those in rice, whereas downstream genes regulated by ZmFIT show similarities to rice but differences from Arabidopsis. In brief, ZmFIT, orthgologs of OsFIT and AtFIT in rice and maize, respectively, regulates iron uptake and homeostasis in maize, but with variations.

GTs (Glycosyltransferases) are important in plant growth and abiotic stresses. However, its role in maize heat response is far from clear. Here, we describe the constitutively expressed UDP-glycosyltransferase ZmUGT92A1, which has a highly conserved PSPG box and is localized in chloroplasts, is induced under heat stress. Functional disruption of ZmUGT92A1 leads to heat sensitivity and reactive oxygen species accumulation in maize. Metabolomics analysis revealed that ZmUGT92A1 affected multiple metabolic pathways and altered the metabolic homeostasis of flavonoids under heat stress. In vitro assay showed ZmUGT92A1 exhibits glycosyltransferase activity on flavonoids and hormones. Additionally, we identified a rapidly heat-induced transcription factor, ZmHSF08, which can directly bind and repress the promoter region of ZmUGT92A1. The ZmHSF08 overexpression line exhibits heat sensitivity and reactive oxygen species accumulation. These findings reveal that the ZmHSF08-ZmUGT92A1 module plays a role in heat tolerance in maize and provide candidate strategies for the development of heat-tolerant varieties.

Plant Homeo Domain (PHD) proteins are involved in diverse biological processes during plant growth. However, the regulation of PHD genes on rice cold stress response remains largely unknown. Here, we reported that PHD17 negatively regulated cold tolerance in rice seedlings as a cleavage target of miR1320. PHD17 expression was greatly induced by cold stress, and was down-regulated by miR1320 overexpression and up-regulated by miR1320 knockdown. Through 5′RACE and dual luciferase assays, we found that miR1320 targeted and cleaved the 3′UTR region of PHD17. PHD17 was a nuclear-localized protein and acted as a transcriptional activator in yeast. PHD17 overexpression reduced cold tolerance of rice seedlings, while knockout of PHD17 increased cold tolerance, partially via the CBF cold signaling. By combining transcriptomic and physiological analyses, we demonstrated that PHD17 modulated ROS homeostasis and flavonoid accumulation under cold stress. K-means clustering analysis revealed that differentially expressed genes in PHD17 transgenic lines were significantly enriched in the jasmonic acid (JA) biosynthesis pathway, and expression of JA biosynthesis and signaling genes was verified to be affected by PHD17. Cold stress tests applied with MeJA or IBU (JA synthesis inhibitor) further suggested the involvement of PHD17 in JA-mediated cold signaling. Taken together, our results suggest that PHD17 acts downstream of miR1320 and negatively regulates cold tolerance of rice seedlings through JA-mediated signaling pathway.

A rice low temperature-induced albino variant was determined by the recessive ltia1 and ltia2 genes. LTIA1 and LTIA2 encode highly conserved mini-ribonucleases III located in chloroplasts and expressed in aerial parts of the plant. At low temperature, LTIA1 and LTIA2 redundantly affect chlorophyll levels, non-photochemical quenching, photosynthetic quantum yield of PS II and seedling growth. LTIA1 and LTIA2 proteins are involved in splicing of atpF and the biogenesis of 16S and 23S rRNA in chloroplasts. Presence/absence variation of LTIA1, the ancestral copy, was found only in japonica but that of LTIA2 in all rice subgroups. Accessions with LTIA2 presence tended to be distributed more remote from the equator compared to those with LTIA2 absence. LTIA2 duplicated from LTIA1 at the early stage of divergence of the AA genome Oryza species but deleted againin O. nivara. In cultivated rice, absence of LTIA2 is derived from O. nivara. LTIA1 absence occurred more recently in japonica.

Maintenance of ion homeostasis in plant cells is an essential physiological requirement for sustainable growth, development, and yield of crops. Plants respond to high levels of heavy metals such as copper (Cu) and cadmium (Cd) to avoid irreversible damage at the structural, physiological and molecular levels. Our previous study found that rice germin-like proteins (OsGLPs) are a type of Cu-responsive proteins. The deletion of 10 tandem OsGLP genes on chromosome 8 led to more severe heavy metal toxicity in rice. In this study, we show that rice WRKY transcription factor OsWRKY72 negatively regulates OsGLP8-7 transcription. Overexpression of OsWRKY72 weakens the Cu/Cd tolerance of rice when exposed to Cu and Cd. OsWRKY72 suppressed expression of OsGLP8-7 and lignin synthesis genes, resulting in reduced lignin polymerization and consequently lower lignin accumulation in cell walls, thereby increasing the Cu and Cd accumulation. In addition, OsWRKY53 bound to OsWRKY72 to alleviate the transcriptional inhibition of OsGLP8-7. These results revealed that OsWRKY72-OsGLP8-7 is an important module response of rice to heavy metal stress, and that transcription factor OsWRKY72 acts upstream of OsGLP8-7 to regulate Cu/Cd toxicity.

Aluminum (Al) toxicity poses a significant constraint on field crop yields in acid soils. Zinc finger protein 36 (ZFP36) is well-documented for its pivotal role in enhancing tolerance to both drought and oxidative stress in rice. This study unveils a novel function of ZFP36 modulated by abscisic acid (ABA)-dependent mechanisms, specifically aimed at alleviating Al toxicity in rice. Under Al stress, the expression of ZFP36 significantly increased through an ABA-dependent pathway. Knocking down ZFP36 heightened Al sensitivity, while overexpressing ZFP36 conferred increased resistance to Al stress. Additionally, our investigations revealed a physical interaction between ZFP36 and pyruvate dehydrogenase kinase 1 in rice (OsPDK1). Biochemical assays further elucidated that OsPDK1 phosphorylates ZFP36 at the amino acid site 73-161. Subsequent experiments demonstrated that ZFP36 positively regulates the expression of ascorbate peroxidases (OsAPX1) and OsALS1 by binding to specific elements in their upstream segments in rice. Through genetic and phenotypic analyses, we unveiled that OsPDK1 influences ABA-triggered antioxidant defense to alleviate Al toxicity by interacting with ZFP36. In summary, our study underscores that pyruvate dehydrogenase kinase 1 (OsPDK1) phosphorylates ZFP36 to modulate the activities of antioxidant enzymes via an ABA-dependent pathway, influencing tolerance of rice to soil Al toxicity.

Soil salinity seriously affects the utilization of farmland and threatens the crop production. Here, a selenium-nitrogen-co-doped carbon dots was developed, which increased rice seedling growth and alleviated its inhibition by salt stress by foliar spraying. The treatment activated Ca²⁺ and jasmonic acid signaling pathways and increased iron homeostasis, antioxidant defense, and cell wall development of rice seedlings. It could be used to increase crop resistance to environmental stress.