A wheat CCAAT box-binding transcription factor increases the grain yield of wheat with less fertilizer input

Ethylene modulates wheat response to phosphate deficiency

Ethylene is involved in the response to P deficiency in some model plants such as Arabidopsis and rice, but its role in wheat remains unclear. Following our recent study demonstrating the role of differentially expressed genes encoding ethylene response factors (ERFs) in response to P starvation in wheat, this study aims to investigate remodeling of the ethylene pathway and the physiological roles of ethylene in wheat under P deficiency using transcriptome analysis and the addition of the exogenous ethylene analogue, ethephon, or ethylene inhibitors. ERFs with at least a 2-fold expression change upon P deficiency had a distribution biased towards chromosome 4B. A group of genes encoding aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase were up-regulated under P starvation, suggesting an increase in ACC and ethylene content, which was verified by biochemical measurements and gas chromatography-mass spectrometry analysis. Under P deficiency, both root and shoot biomass decreased with application of exogenous ethephon or ethylene inhibitors, while root fork numbers and root surface area decreased upon ethephon treatment. Phosphate (Pi) concentrations in roots and old leaves increased with ethephon treatment, and Pi redistribution in roots and younger leaves was altered under Pi starvation. Our findings can guide breeding of germplasm with high Pi efficiency.

MicroRNA gatekeepers: Orchestrating rhizospheric dynamics

The rhizosphere plays a crucial role in plant growth and resilience to biotic and abiotic stresses, highlighting the complex communication between plants and their dynamic rhizosphere environment. Plants produce a wide range of signaling molecules that facilitate communication with various rhizosphere factors, yet our understanding of these mechanisms remains elusive. In addition to protein-coding genes, increasing evidence underscores the critical role of microRNAs (miRNAs), a class of non-coding single-stranded RNA molecules, in regulating plant growth, development, and responses to rhizosphere stresses under diverse biotic and abiotic factors. In this review, we explore the crosstalk between miRNAs and their target mRNAs, which influence the development of key plant structures shaped by the belowground environment. Moving forward, more focused studies are needed to clarify the functions and expression patterns of miRNAs, to uncover the common regulatory mechanisms that mediate plant tolerance to rhizosphere dynamics. Beyond that, we propose that using artificial miRNAs and manipulating the expression of miRNAs and their targets through overexpression or knockout/knockdown approaches could effectively investigate their roles in plant responses to rhizosphere stresses, offering significant potential for advancing crop engineering.

The soybean NUCLEAR FACTOR-Y C4 and α-EXPANSIN 7 module influences phosphorus uptake by regulating root morphology

Soybean (Glycine max) is a globally important crop; however, its productivity is severely impacted by phosphorus (P) deficiency. Understanding the transcriptional regulation of low P (LP) response mechanisms is essential for enhancing soybean P use efficiency. In this study, we found that the Nuclear Factor-Y (NF-Y) transcription factor GmNF-YC4, in addition to its previously discovered role in regulating flowering time, possesses other functions in modulating root morphology and P uptake. Knockout of GmNF-YC4 notably boosted root proliferation and P uptake while also influencing the expression of genes related to LP stress. GmNF-YC4 acts as a specific DNA-binding transcriptional repressor, modulating the expression of the soybean α-EXPANSIN 7 (GmEXPA7) gene, which encodes a cell-wall-loosening factor, through direct binding to its promoter region. Further investigation revealed that GmEXPA7 expression is predominantly root-specific and induced by LP. Moreover, overexpression of GmEXPA7 in soybean hairy roots enhanced LP tolerance by stimulating root growth and P uptake. We further screened and obtained more potential target genes of GmNF-YC4 via DNA affinity purification sequencing, including those related to LP stress. These findings underscore the pivotal role of the GmNF-YC4-GmEXPA7 module as a key regulator in mitigating LP stress in soybeans.

Integrated analysis of BSA-seq and RNA-seq identified the candidate genes for seed weight in Brassica juncea

Introduction

Brassica juncea is a major oilseed crop of Brassica. The seed weight is one of yield components in oilseed Brassica crops. Research on the genetic mechanism of seed weight is not only directly related to the yield and economic value of Brassica juncea but also can provide a theory foundation for studying other Brassica crops.

Methods

To map the genes for seed weight, the parental and F2 extreme bulks derived were constructed from the cross between the heavy-seeded accession 7981 and the light-seeded one Sichuan yellow (SY) of B. juncea, and used in bulk segregant sequencing (BSA-seq). Meanwhile, RNA-sequencing (RNA-seq) was performed for both parents at six seed development stages.

Results

Our results showed that a total of thirty five SNPs were identified in thirty two genes located on chromosomes A02 and A10, while fifty eight InDels in fifty one genes located on A01, A03, A05, A07, A09, A10, B01, B02 and B04. The 7,679 differentially expressed genes were identified in developing seeds between the parents. Furthermore, integrated analysis of BSA-seq and RNA-seq data revealed a cluster of nine genes on chromosome A10 and one gene on chromosome A05 that are putative candidate genes controlling seed weight in B. juncea.

Discussion

This study provides a new reference for research on Brassica seed weight and lays a solid foundation for the examination of seed in other Brassica crops.

Functional and biotechnological cues of potassium homeostasis for stress tolerance and plant development

Potassium (K+) is indispensable for the regulation of a plethora of functions like plant metabolism, growth, development, and abiotic stress responses. K+ is associated with protein synthesis and entangled in the activation of scores of enzymes, stomatal regulation, and photosynthesis. It has multiple transporters and channels that assist in the uptake, efflux, transport within the cell as well as from soil to different tissues, and the grain filling sites. While it is implicated in ion homeostasis during salt stress, it acts as a modulator of stomatal movements during water deficit conditions. K+ is reported to abate the effects of chilling and photooxidative stresses. K+ has been found to ameliorate effectively the co-occurrence of drought and high-temperature stresses. Nutrient deficiency of K+ makes leaves necrotic, leads to diminished photosynthesis, and decreased assimilate utilization highlighting the role it plays in photosynthesis. Notably, K+ is associated with the detoxification of reactive oxygen species (ROS) when plants are exposed to diverse abiotic stress conditions. It is irrefutable now that K+ reduces the activity of NADPH oxidases and at the same time maintains electron transport activity, which helps in mitigating the oxidative stress. K+ as a macronutrient in plant growth, the role of K+ during abiotic stress and the protein phosphatases involved in K+ transport have been reviewed. This review presents a holistic view of the biological functions of K+, its uptake, translocation, signaling, and the critical roles it plays under abiotic stress conditions, plant growth, and development that are being unraveled in recent times.

MicroRNAs as potent regulators in nitrogen and phosphorus signaling transduction and their applications

Nitrogen (N) and phosphorus (Pi) are essential macronutrients that affect plant growth and development by influencing the molecular, metabolic, biochemical, and physiological responses at the local and whole levels in plants. N and Pi stresses suppress the physiological activities of plants, resulting in agricultural productivity losses and severely threatening food security. Accordingly, plants have elaborated diverse strategies to cope with N and Pi stresses through maintaining N and Pi homeostasis. MicroRNAs (miRNAs) as potent regulators fine-tune N and Pi signaling transduction that are distinct and indivisible from each other. Specific signals, such as noncoding RNAs (ncRNAs), interact with miRNAs and add to the complexity of regulation. Elucidation of the mechanisms by which miRNAs regulate N and Pi signaling transduction aids in the breeding of plants with strong tolerance to N and Pi stresses and high N and Pi use efficiency by fine-tuning MIR genes or miRNAs. However, to date, there has been no detailed and systematic introduction and comparison of the functions of miRNAs in N and Pi signaling transduction from the perspective of miRNAs and their applications. Here, we summarized and discussed current advances in the involvement of miRNAs in N and Pi signaling transduction and highlighted that fine-tuning the MIR genes or miRNAs involved in maintaining N and Pi homeostasis might provide valuable sights for sustainable agriculture.

Identification and expression analysis of nuclear factor Y transcription factor genes under drought, cold and Eldana infestation in sugarcane (Saccharum spp. hybrid)

BACKGROUND

The Nuclear Factor Y (NF-Y) transcription factor (TF) gene family plays a crucial role in plant development and response to stress. Limited information is available on this gene family in sugarcane.

OBJECTIVES

To identify sugarcane NF-Y genes through bioinformatic analysis and phylogenetic association and investigate the expression of these genes in response to abiotic and biotic stress.

METHODS

Sugarcane NF-Y genes were identified using comparative genomics from functionally annotated Poaceae and Arabidopsis species. Quantitative PCR and transcriptome analysis assigned preliminary functional roles to these genes in response to water deficit, cold and African sugarcane borer (Eldana saccharina) infestation.

RESULTS

We identify 21 NF-Y genes in sugarcane. Phylogenetic analysis revealed three main branches representing the subunits with potential discrepancies present in the assignment of numerical names of some NF-Y putative orthologs across the different species. Gene expression analysis indicated that three genes, ShNF-YA1, A3 and B3 were upregulated and two genes, NF-YA4 and A7 were downregulated, while three genes were upregulated, ShNF-YB2, B3 and C4, in the plants exposed to water deficit and cold stress, respectively. Functional involvement of NF-Y genes in the biotic stress response were also detected where three genes, ShNF-YA6, A3 and A7 were downregulated in the early resistant (cv. N33) response to Eldana infestation whilst only ShNF-YA6 was downregulated in the susceptible (cv. N11) early response.

CONCLUSIONS

Our research findings establish a foundation for investigating the function of ShNF-Ys and offer candidate genes for stress-resistant breeding and improvement in sugarcane.

Interplay between nitric oxide and inorganic nitrogen sources in root development and abiotic stress responses

Nitrogen (N) is an essential nutrient for plants, and the sources from which it is obtained can differently affect their entire development as well as stress responses. Distinct inorganic N sources (nitrate and ammonium) can lead to fluctuations in the nitric oxide (NO) levels and thus interfere with nitric oxide (NO)-mediated responses. These could lead to changes in reactive oxygen species (ROS) homeostasis, hormone synthesis and signaling, and post-translational modifications of key proteins. As the consensus suggests that NO is primarily synthesized in the reductive pathways involving nitrate and nitrite reduction, it is expected that plants grown in a nitrate-enriched environment will produce more NO than those exposed to ammonium. Although the interplay between NO and different N sources in plants has been investigated, there are still many unanswered questions that require further elucidation. By building on previous knowledge regarding NO and N nutrition, this review expands the field by examining in more detail how NO responses are influenced by different N sources, focusing mainly on root development and abiotic stress responses.

The ZmNF-YC1-ZmAPRG pathway modulates low phosphorus tolerance in maize

Phosphorus (P) is an essential nutrient for plant growth and yield. Low phosphate use efficiency makes it important to clarify the molecular mechanism of low P stress. In our previous studies, a P efficiency gene ZmAPRG was identified. Here, we further screened the upstream regulator ZmNF-YC1 of ZmAPRG by yeast one hybrid (Y1H) assay, and found it was a low inorganic phosphorus (Pi)-inducible gene. The results of dual luciferase assays, expression analysis, and ChIP-qPCR assays showed that ZmNF-YC1 is a positive regulator of ZmAPRG. Overexpression of ZmNF-YC1 improved low P tolerance, whereas knockout of ZmNF-YC1 decreased low P tolerance in maize. Bimolecular fluorescence complementation (BiFC), yeast two hybrid (Y2H) assay, and yeast three hybrid (Y3H) assay further showed that ZmNF-YC1 can interact with ZmNF-YB14, and recruit ZmNF-YA4/10 to form NF-Y complexes. Transcriptional activation assay confirmed that the NF-Y complexes can activate the promoters of ZmAPRG. Meanwhile, transcriptome and metabolome analyses indicated that overexpression of ZmAPRG improves low P tolerance by regulating lipid composition and photosynthetic capacity, and chlorophyll fluorescence parameters provided evidence in support of this hypothesis. Furthermore, overexpression of ZmAPRG increased grain yield in inbred and hybrid maize under low P conditions. Taken together, our research revealed a low P tolerance mechanism of the ZmNF-YC1-ZmAPRG pathway.

Comparative transcriptomic and physiological analyses unravel wheat source root adaptation to phosphorous deficiency

Phosphorus (P) is a crucial macronutrient for plant growth and development. Basic metabolic processes regulate growth; however, the molecular detail of these pathways under low phosphorous (LP) in wheat is still unclear. This study aims to elucidate the varied regulatory pathways responses to LP stress in wheat genotypes. Phenotypic, physiological, and transcriptome analyses were conducted on Fielder (P efficient) and Ardito (P inefficient) wheat genotypes after four days of normal phosphorous (NP) and LP stress. In response to LP, Fielder outperformed Ardito, displaying higher chlorophyll content-SPAD values (13%), plant height (45%), stem diameter (12%), shoot dry weight (42%), and root biomass (75%). Root structure analysis revealed that Fielder had greater total root length (50%), surface area (56%), volume (15%), and diameter (4%) than Ardito under LP. These findings highlight Fielder's superior performance and adaptation to LP stress. Transcriptome analysis of wheat genotype roots identified 3029 differentially expressed genes (DEGs) in Fielder and 1430 in Ardito, highlighting LP-induced changes. Key DEGs include acid phosphatases (PAPs), phosphate transporters (PHT1 and PHO1), SPX, and transcription factors (MYB, bHLH, and WRKY). KEGG enrichment analysis revealed key pathways like plant hormones signal transduction, biosynthesis of secondary metabolites, and carbohydrate biosynthesis metabolism. This study unveils crucial genes and the intricate regulatory process in wheat's response to LP stress, offering genetic insights for enhancing plant P utilization efficiency.

Expression profiling of Nuclear Factor-Y (NF-Y) transcription factors during dehydration and salt stress in finger millet reveals potential candidate genes for multiple stress tolerance

MAIN CONCLUSION

Expression profiling of NF-Y transcription factors during dehydration and salt stress in finger millet genotypes contrastingly differing in tolerance levels identifies candidate genes for further characterization and functional studies. The Nuclear Factor-Y (NF-Y) transcription factors are known for imparting abiotic stress tolerance in different plant species. However, there is no information on the role of this transcription factor family in naturally drought-tolerant crop finger millet (Eleusine coracana L.). Therefore, interpretation of expression profiles against drought and salinity stress may provide valuable insights into specific and/or overlapping expression patterns of Eleusine coracana Nuclear Factor-Y (EcNF-Y) genes. Given this, we identified 59 NF-Y (18 NF-YA, 23 NF-YB, and 18 NF-YC) encoding genes and designated them EcNF-Y genes. Expression profiling of these genes was performed in two finger millet genotypes, PES400 (dehydration and salt stress tolerant) and VR708 (dehydration and salt stress sensitive), subjected to PEG-induced dehydration and salt (NaCl) stresses at different time intervals (0, 6, and 12 h). The qRT-PCR expression analysis reveals that the six EcNF-Y genes namely EcNF-YA1, EcNF-YA5, EcNF-YA16, EcNF-YB6, EcNF-YB10, and EcNF-YC2 might be associated with tolerance to both dehydration and salinity stress in early stress condition (6 h), suggesting the involvement of these genes in multiple stress responses in tolerant genotype. In contrast, the transcript abundance of finger millet EcNF-YA5 genes was also observed in the sensitive genotype VR708 under late stress conditions (12 h) of both dehydration and salinity stress. Therefore, the EcNF-YA5 gene might be important for adaptation to salinity and dehydration stress in sensitive finger millet genotypes. Therefore, this gene could be considered as a susceptibility determinant, which can be edited to impart tolerance. The phylogenetic analyses revealed that finger millet NF-Y genes share strong evolutionary and functional relationship to NF-Ys governing response to abiotic stresses in rice, sorghum, maize, and wheat. This is the first report of expression profiling of EcNF-Ys genes identified from the finger millet genome and reveals potential candidate for enhancing dehydration and salt tolerance.

TaLBD41 interacts with TaNAC2 to regulate nitrogen uptake and metabolism in response to nitrate availability

Nitrate is the main source of nitrogen (N) available to plants and also is a signal that triggers complex regulation of transcriptional networks to modulate a wide variety of physiological and developmental responses in plants. How plants adapt to soil nitrate fluctuations is a complex process involving a fine-tuned response to nitrate provision and N starvation, the molecular mechanisms of which remain largely uncharted. Here, we report that the wheat transcription factor TaLBD41 interacts with the nitrate-inducible transcription factor TaNAC2 and is repressed by nitrate provision. Electrophoretic mobility shift assay and dual-luciferase system show that the TaLBD41-NAC2 interaction confers homeostatic coordination of nitrate uptake, reduction, and assimilation by competitively binding to TaNRT2.1, TaNR1.2, and TaNADH-GOGAT. Knockdown of TaLBD41 expression enhances N uptake and assimilation, increases spike number, grain yield, and nitrogen harvest index under different N supply conditions. We also identified an elite haplotype of TaLBD41-2B associated with increased spike number and grain yield. Our study uncovers a novel mechanism underlying the interaction between two transcription factors in mediating wheat adaptation to nitrate availability by antagonistically regulating nitrate uptake and assimilation, providing a potential target for designing varieties with efficient N use in wheat (Triticum aestivum).

The water-retaining functional slow-release fertilizer modified by carboxymethyl chitosan

To solve the problem of shortage of agricultural water resources and low utilization rate of fertilizer, a slow-release fertilizer based on chitosan modified water retention function was developed. Solution polymerization and semi-interpenetrating network technology were used to load urea aldehyde into carboxymethyl chitosan superabsorbent resin network. This technology realizes the simultaneous slow release of nutrients and water by using modified chitosan, which has important implications for the application of chitosan in agriculture to regulate the soil water and fertilizer conditions. The optimal preparation conditions were: MBA 0.07 %, KPS 0.8 %, AM to AA mass ratio of 0.3:1, CMC content of 10 %, AA neutralization degree 85 %, UF 20 %, AA+AM mass sum of 10 g, reaction temperature 70 °C and reaction time 2 h. The maximum water absorption rate of the optimized NC reached 172.3 g/g. The cumulative release of nitrogen in 30 days was 83.67 %. The application of NC in sandy soil promoted seed germination and growth. The comprehensive results indicate that NC has broad application prospects in arid areas based on its excellent water retention and nutrient release performance.

The rice NUCLEAR FACTOR-YA5 and MICRORNA169a module promotes nitrogen utilization during nitrogen deficiency

Nitrogen (N) is essential for plant growth and development. Therefore, understanding its utilization is essential for improving crop productivity. However, much remains to be learned about plant N sensing and signaling. Here, rice (Oryza sativa) NUCLEAR FACTOR-YA5 (OsNF-YA5) expression was tightly regulated by N status and induced under N-deficient conditions. Overexpression (OE) of OsNF-YA5 in rice resulted in increased chlorophyll levels and delayed senescence compared to control plants under normal N conditions. Agronomic traits were significantly improved in OE plants and impaired in knockout mutants under N-deficient conditions. Using a dexamethasone-inducible system, we identified the putative targets of OsNF-YA5 that include amino acid, nitrate/peptide transporters, and NITRATE TRANSPORTER 1.1A (OsNRT1.1A), which functions as a key transporter in rice. OsNF-YA5 directly enhanced OsNRT1.1A expression and N uptake rate under N-deficient conditions. Besides, overexpression of OsNF-YA5 also enhanced the expression of GLUTAMINE SYNTHETASE 1/2 (GS1/2) and GLUTAMINE OXOGLUTARATE AMINOTRANSFERASE 1/2 (GOGAT1/2), increasing free amino acid contents under N-deficient conditions. Osa-miR169a expression showed an opposite pattern with OsNF-YA5 depending on N status. Further analysis revealed that osa-miR169a negatively regulates OsNF-YA5 expression and N utilization, demonstrating that an OsNF-YA5/osa-miR169a module tightly regulates rice N utilization for adaptation to N status.

Phosphate starvation: response mechanisms and solutions

Phosphorus is essential to plant growth and agricultural crop yields, yet the challenges associated with phosphorus fertilization in agriculture, such as aquatic runoff pollution and poor phosphorus bioavailability, are increasingly difficult to manage. Comprehensively understanding the dynamics of phosphorus uptake and signaling mechanisms will inform the development of strategies to address these issues. This review describes regulatory mechanisms used by specific tissues in the root apical meristem to sense and take up phosphate from the rhizosphere. The major regulatory mechanisms and related hormone crosstalk underpinning phosphate starvation responses, cellular phosphate homeostasis, and plant adaptations to phosphate starvation are also discussed, along with an overview of the major mechanism of plant systemic phosphate starvation responses. Finally, this review discusses recent promising genetic engineering strategies for improving crop phosphorus use and computational approaches that may help further design strategies for improved plant phosphate acquisition. The mechanisms and approaches presented include a wide variety of species including not only Arabidopsis but also crop species such as Oryza sativa (rice), Glycine max (soybean), and Triticum aestivum (wheat) to address both general and species-specific mechanisms and strategies. The aspects of phosphorus deficiency responses and recently employed strategies of improving phosphate acquisition that are detailed in this review may provide insights into the mechanisms or phenotypes that may be targeted in efforts to improve crop phosphorus content and plant growth in low phosphorus soils.

miRNA mediated regulation of nitrogen response and nitrogen use efficiency of plants: the case of wheat

Nitrogen (N) is needed for plant growth and development and is the major limiting nutrient due to its higher demand in agricultural production globally. The use of N fertilizers has increased considerably in recent years to achieve higher cereal yields. High N inputs coupled with declining N use efficiency (NUE) result in the degradation of the environment. Plants have developed multidimensional strategies in response to changes in N availability in soil. These strategies include N stress-induced responses such as changes in gene expression patterns. Several N stress-induced genes and other regulatory factors, such as microRNAs (miRNAs), have been identified in different plant species, opening a new avenue of research in plant biology. This review presents a general overview of miRNA-mediated regulation of N response and NUE. Further, the in-silico target predictions and the predicted miRNA-gene network for nutrient metabolism/homeostasis in wheat provide novel insights. The information on N-regulated miRNAs and the differentially expressed target transcripts are necessary resources for genetic improvement of NUE by genome editing.

Noncoding RNAs and their roles in regulating the agronomic traits of crops

Molecular breeding is one of the most effective methods for improving the performance of crops. Understanding the genome features of crops, especially the physiological functions of individual genes, is of great importance to molecular breeding. Evidence has shown that genomes of both animals and plants transcribe numerous non-coding RNAs, which are involved in almost every aspect of development. In crops, an increasing number of studies have proven that non-coding RNAs are new genetic resources for regulating crop traits. In this review, we summarize the current knowledge of non-coding RNAs, which are potential crop trait regulators, and focus on the functions of long non-coding RNAs (lncRNAs) in determining crop grain yield, phased small-interfering RNAs (phasiRNAs) in regulating fertility, small interfering RNAs (siRNAs) and microRNAs (miRNAs) in facilitating plant immune response and disease resistance, and miRNAs mediating nutrient and metal stress. Finally, we also discuss the next-generation method for ncRNA application in crop domestication and breeding.

Epigenetic Regulation of Nitrogen Signaling and Adaptation in Plants

Nitrogen (N) is a crucial nutrient that plays a significant role in enhancing crop yield. Its availability, including both supply and deficiency, serves as a crucial signal for plant development. However, excessive N use in agriculture leads to environmental and economic issues. Enhancing nitrogen use efficiency (NUE) is, therefore, essential to minimize negative impacts. Prior studies have investigated the genetic factors involved in N responses and the process of low-nitrogen (LN) adaptation. In this review, we discuss recent advances in understanding how epigenetic modifications, including DNA methylation, histone modification, and small RNA, participate in the regulation of N response and LN adaptation. We highlight the importance of decoding the epigenome at various levels to accelerate the functional study of how plants respond to N availability. Understanding the epigenetic control of N signaling and adaptation can lead to new strategies to improve NUE and enhance crop productivity sustainably.

"Millet Models" for harnessing nuclear factor-Y transcription factors to engineer stress tolerance in plants: current knowledge and emerging paradigms

MAIN CONCLUSION

The main purpose of this review is to shed light on the role of millet models in imparting climate resilience and nutritional security and to give a concrete perspective on how NF-Y transcription factors can be harnessed for making cereals more stress tolerant. Agriculture faces significant challenges from climate change, bargaining, population, elevated food prices, and compromises with nutritional value. These factors have globally compelled scientists, breeders, and nutritionists to think of some options that can combat the food security crisis and malnutrition. To address these challenges, mainstreaming the climate-resilient and nutritionally unparalleled alternative crops like millet is a key strategy. The C4 photosynthetic pathway and adaptation to low-input marginal agricultural systems make millets a powerhouse of important gene and transcription factor families imparting tolerance to various kinds of biotic and abiotic stresses. Among these, the nuclear factor-Y (NF-Y) is one of the prominent transcription factor families that regulate diverse genes imparting stress tolerance. The primary purpose of this article is to shed light on the role of millet models in imparting climate resilience and nutritional security and to give a concrete perspective on how NF-Y transcription factors can be harnessed for making cereals more stress tolerant. Future cropping systems could be more resilient to climate change and nutritional quality if these practices were implemented.

Genome-Wide Identification, Characterization and Expression Analysis of Plant Nuclear Factor (NF-Y) Gene Family Transcription Factors in Saccharum spp

Plant nuclear factor (NF-Y) is a transcriptional activating factor composed of three subfamilies: NF-YA, NF-YB, and NF-YC. These transcriptional factors are reported to function as activators, suppressors, and regulators under different developmental and stress conditions in plants. However, there is a lack of systematic research on the NF-Y gene subfamily in sugarcane. In this study, 51 NF-Y genes (ShNF-Y), composed of 9 NF-YA, 18 NF-YB, and 24 NF-YC genes, were identified in sugarcane (Saccharum spp.). Chromosomal distribution analysis of ShNF-Ys in a Saccharum hybrid located the NF-Y genes on all 10 chromosomes. Multiple sequence alignment (MSA) of ShNF-Y proteins revealed conservation of core functional domains. Sixteen orthologous gene pairs were identified between sugarcane and sorghum. Phylogenetic analysis of NF-Y subunits of sugarcane, sorghum, and Arabidopsis showed that ShNF-YA subunits were equidistant while ShNF-YB and ShNF-YC subunits clustered distinctly, forming closely related and divergent groups. Expression profiling under drought treatment showed that NF-Y gene members were involved in drought tolerance in a Saccharum hybrid and its drought-tolerant wild relative, Erianthus arundinaceus. ShNF-YA5 and ShNF-YB2 genes had significantly higher expression in the root and leaf tissues of both plant species. Similarly, ShNF-YC9 had elevated expression in the leaf and root of E. arundinaceus and in the leaf of a Saccharum hybrid. These results provide valuable genetic resources for further sugarcane crop improvement programs.

Comprehensive Analysis of the NF-YB Gene Family and Expression under Abiotic Stress and Hormone Treatment in Larix kaempferi

NF-YB, a subfamily of Nuclear Factor Y (NF-Y) transcription factor, play crucial role in many biological processes of plant growth and development and abiotic stress responses, and they can therefore be good candidate factors for breeding stress-resistant plants. However, the NF-YB proteins have not yet been explored in Larix kaempferi, a tree species with high economic and ecological values in northeast China and other regions, limiting the breeding of anti-stress L. kaempferi. In order to explore the roles of NF-YB transcription factors in L. kaempferi, we identified 20 LkNF-YB family genes from L. kaempferi full-length transcriptome data and carried out preliminary characterization of them through series of analyses on their phylogenetic relationships, conserved motif structure, subcellular localization prediction, GO annotation, promoter cis-acting elements as well as expression profiles under treatment of phytohormones (ABA, SA, MeJA) and abiotic stresses (salt and drought). The LkNF-YB genes were classified into three clades through phylogenetic analysis and belong to non-LEC1 type NF-YB transcription factors. They have 10 conserved motifs; all genes contain a common motif, and their promoters have various phytohormones and abiotic stress related cis-acting elements. Quantitative real time reverse transcription PCR (RT-qPCR) analysis showed that the sensitivity of the LkNF-YB genes to drought and salt stresses was higher in leaves than roots. The sensitivity of LKNF-YB genes to ABA, MeJA, SA stresses was much lower than that to abiotic stress. Among the LkNF-YBs, LkNF-YB3 showed the strongest responses to drought and ABA treatments. Further protein interaction prediction analysis for LkNF-YB3 revealed that LkNF-YB3 interacts with various factors associated with stress responses and epigenetic regulation as well as NF-YA/NF-YC factors. Taken together, these results unveiled novel L. kaempferi NF-YB family genes and their characteristics, providing the basic knowledge for further in-depth studies on their roles in abiotic stress responses of L. kaempferi.

Current Progress and Future Prospect of Wheat Genetics Research towards an Enhanced Nitrogen Use Efficiency

To improve the yield and quality of wheat is of great importance for food security worldwide. One of the most effective and significant approaches to achieve this goal is to enhance the nitrogen use efficiency (NUE) in wheat. In this review, a comprehensive understanding of the factors involved in the process of the wheat nitrogen uptake, assimilation and remobilization of nitrogen in wheat were introduced. An appropriate definition of NUE is vital prior to its precise evaluation for the following gene identification and breeding process. Apart from grain yield (GY) and grain protein content (GPC), the commonly recognized major indicators of NUE, grain protein deviation (GPD) could also be considered as a potential trait for NUE evaluation. As a complex quantitative trait, NUE is affected by transporter proteins, kinases, transcription factors (TFs) and micro RNAs (miRNAs), which participate in the nitrogen uptake process, as well as key enzymes, circadian regulators, cross-talks between carbon metabolism, which are associated with nitrogen assimilation and remobilization. A series of quantitative genetic loci (QTLs) and linking markers were compiled in the hope to help discover more efficient and useful genetic resources for breeding program. For future NUE improvement, an exploration for other criteria during selection process that incorporates morphological, physiological and biochemical traits is needed. Applying new technologies from phenomics will allow high-throughput NUE phenotyping and accelerate the breeding process. A combination of multi-omics techniques and the previously verified QTLs and molecular markers will facilitate the NUE QTL-mapping and novel gene identification.

Crucial Abiotic Stress Regulatory Network of NF-Y Transcription Factor in Plants

Nuclear Factor-Y (NF-Y), composed of three subunits NF-YA, NF-YB and NF-YC, exists in most of the eukaryotes and is relatively conservative in evolution. As compared to animals and fungi, the number of NF-Y subunits has significantly expanded in higher plants. The NF-Y complex regulates the expression of target genes by directly binding the promoter CCAAT box or by physical interaction and mediating the binding of a transcriptional activator or inhibitor. NF-Y plays an important role at various stages of plant growth and development, especially in response to stress, which attracted many researchers to explore. Herein, we have reviewed the structural characteristics and mechanism of function of NF-Y subunits, summarized the latest research on NF-Y involved in the response to abiotic stresses, including drought, salt, nutrient and temperature, and elaborated the critical role of NF-Y in these different abiotic stresses. Based on the summary above, we have prospected the potential research on NF-Y in response to plant abiotic stresses and discussed the difficulties that may be faced in order to provide a reference for the in-depth analysis of the function of NF-Y transcription factors and an in-depth study of plant responses to abiotic stress.

Unlocking the potentials of nitrate transporters at improving plant nitrogen use efficiency

Nitrate ( NO 3 - ) transporters have been identified as the primary targets involved in plant nitrogen (N) uptake, transport, assimilation, and remobilization, all of which are key determinants of nitrogen use efficiency (NUE). However, less attention has been directed toward the influence of plant nutrients and environmental cues on the expression and activities of NO 3 - transporters. To better understand how these transporters function in improving plant NUE, this review critically examined the roles of NO 3 - transporters in N uptake, transport, and distribution processes. It also described their influence on crop productivity and NUE, especially when co-expressed with other transcription factors, and discussed these transporters' functional roles in helping plants cope with adverse environmental conditions. We equally established the possible impacts of NO 3 - transporters on the uptake and utilization efficiency of other plant nutrients while suggesting possible strategic approaches to improving NUE in plants. Understanding the specificity of these determinants is crucial to achieving better N utilization efficiency in crops within a given environment.

H+-pyrophosphatases enhance low nitrogen stress tolerance in transgenic Arabidopsis and wheat by interacting with a receptor-like protein kinase

INTRODUCTION

Nitrogen is a major abiotic stress that affects plant productivity. Previous studies have shown that plant H+-pyrophosphatases (H+-PPases) enhance plant resistance to low nitrogen stress. However, the molecular mechanism underlying H+-PPase-mediated regulation of plant responses to low nitrogen stress is still unknown. In this study, we aimed to investigate the regulatory mechanism of AtAVP1 in response to low nitrogen stress.

METHODS AND RESULTS

AtAVP1 in Arabidopsis thaliana and EdVP1 in Elymus dahuricus belong to the H+-PPase gene family. In this study, we found that AtAVP1 overexpression was more tolerant to low nitrogen stress than was wild type (WT), whereas the avp1-1 mutant was less tolerant to low nitrogen stress than WT. Plant height, root length, aboveground fresh and dry weights, and underground fresh and dry weights of EdVP1 overexpression wheat were considerably higher than those of SHI366 under low nitrogen treatment during the seedling stage. Two consecutive years of low nitrogen tolerance experiments in the field showed that grain yield and number of grains per spike of EdVP1 overexpression wheat were increased compared to those in SHI366, which indicated that EdVP1 conferred low nitrogen stress tolerance in the field. Furthermore, we screened interaction proteins in Arabidopsis; subcellular localization analysis demonstrated that AtAVP1 and Arabidopsis thaliana receptor-like protein kinase (AtRLK) were located on the plasma membrane. Yeast two-hybrid and luciferase complementary imaging assays showed that the AtRLK interacted with AtAVP1. Under low nitrogen stress, the Arabidopsis mutants rlk and avp1-1 had the same phenotypes.

DISCUSSION

These results indicate that AtAVP1 regulates low nitrogen stress responses by interacting with AtRLK, which provides a novel insight into the regulatory pathway related to H+-pyrophosphatase function in plants.

Breeding for Higher Yields of Wheat and Rice through Modifying Nitrogen Metabolism

Wheat and rice produce nutritious grains that provide 32% of the protein in the human diet globally. Here, we examine how genetic modifications to improve assimilation of the inorganic nitrogen forms ammonium and nitrate into protein influence grain yield of these crops. Successful breeding for modified nitrogen metabolism has focused on genes that coordinate nitrogen and carbon metabolism, including those that regulate tillering, heading date, and ammonium assimilation. Gaps in our current understanding include (1) species differences among candidate genes in nitrogen metabolism pathways, (2) the extent to which relative abundance of these nitrogen forms across natural soil environments shape crop responses, and (3) natural variation and genetic architecture of nitrogen-mediated yield improvement. Despite extensive research on the genetics of nitrogen metabolism since the rise of synthetic fertilizers, only a few projects targeting nitrogen pathways have resulted in development of cultivars with higher yields. To continue improving grain yield and quality, breeding strategies need to focus concurrently on both carbon and nitrogen assimilation and consider manipulating genes with smaller effects or that underlie regulatory networks as well as genes directly associated with nitrogen metabolism.

Transcriptomic analysis reveals the contribution of QMrl-7B to wheat root growth and development

Roots are the major organs for water and nutrient acquisition and substantially affect plant growth, development and reproduction. Improvements to root system architecture are highly important for the increased yield potential of bread wheat. QMrl-7B, a major stable quantitative trait locus (QTL) that controls maximum root length (MRL), essentially contributes to an improved root system in wheat. To further analyze the biological functions of QMrl-7B in root development, two sets of Triticum aestivum near-isogenic lines (NILs), one with superior QMrl-7B alleles from cultivar Kenong 9204 (KN9204) named NIL^KN9204 and another with inferior QMrl-7B alleles from cultivar Jing 411 (J411) named NIL^J411, were subjected to transcriptomic analysis. Among all the mapped genes analyzed, 4871 genes were identified as being differentially expressed between the pairwise NILs under different nitrogen (N) conditions, with 3543 genes expressed under normal-nitrogen (NN) condition and 2689 genes expressed under low-nitrogen (LN) condition. These genes encode proteins that mainly include N O 3 - transporters, phytohormone signaling components and transcription factors (TFs), indicating the presence of a complex regulatory network involved in root determination. In addition, among the 13524 LN-induced differentially expressed genes (DEGs) detected in this study, 4308 and 2463 were specifically expressed in the NIL^KN9204 and NIL^J411, respectively. These DEGs reflect different responses of the two sets of NILs to varying N supplies, which likely involve LN-induced root growth. These results explain the better-developed root system and increased root vitality conferred by the superior alleles of QMrl-7B and provide a deeper understanding of the genetic underpinnings of root traits, pointing to a valuable locus suitable for future breeding efforts for sustainable agriculture.

Transcription factors ZmNF-YA1 and ZmNF-YB16 regulate plant growth and drought tolerance in maize

The identification of drought stress regulatory genes is crucial for the genetic improvement of maize (Zea mays L.) yield. Nuclear factors Y (NF-Ys) are important transcription factors, but their roles in the drought stress tolerance of plants and underlying molecular mechanisms are largely unknown. In this work, we used yeast two-hybrid screening to identify potential interactors of ZmNF-YB16 and confirmed the interaction between ZmNF-YA1 and ZmNF-YB16-YC17 and between ZmNF-YA7 and ZmNF-YB16-YC17. ZmNF-YB16 interacted with ZmNF-YC17 via its histone fold domain to form a heterodimer in the cytoplasm and then entered the nucleus to form a heterotrimer with ZmNF-YA1 or ZmNF-YA7 under osmotic stress. Overexpression of ZmNF-YA1 improved drought and salt stress tolerance and root development of maize, whereas zmnf-ya1 mutants exhibited drought and salt stress sensitivity. ZmNF-YA1-mediated transcriptional regulation, especially in JA signaling, histone modification, and chromatin remodeling, could underlie the altered stress tolerance of zmnf-ya1 mutant plants. ZmNF-YA1 bound to promoter CCAAT motifs and directly regulated the expression of multiple genes that play important roles in stress responses and plant development. Comparison of ZmNF-YB16- and ZmNF-YA1-regulated genes showed that ZmNF-YA1 and ZmNF-YB16 have similar biological functions in stress responses but varied functions in other biological processes. Taken together, ZmNF-YA1 is a positive regulator of plant drought and salt stress responses and is involved in the root development of maize, and ZmNF-Y complexes with different subunits may have discrepant functions.

MtNF-YC6 and MtNF-YC11 are involved in regulating the transcriptional program of arbuscular mycorrhizal symbiosis

Arbuscular mycorrhizal fungi are obligate symbionts that transfer mineral nutrients to host plants through arbuscules, a fungal structure specialized for exchange for photosynthetic products. MtNF-YC6 and MtNF-YC11, which encode the C subunits of nuclear factor Y (NF-Y) family in Medicago truncatula are induced specifically by arbuscular mycorrhizal symbiosis (AMS). A previous study showed that MtNF-YC6 and MtNF-YC11 are activated in cortical cells of mycorrhizal roots, but the gene functions were unknown. Herein, we identified both MtNF-YB17 and MtNF-YB12 as the interacting partners of MtNF-YC6 and MtNF-YC11 in yeast and plants. MtNF-YB17 was highly induced by AMS and activated in cortical cells only in mycorrhizal roots but MtNF-YB12 was not affected. The formation of B/C heterodimers led the protein complexes to transfer from the cytoplasm to the nucleus. Silencing MtNF-YC6 and C11 by RNA interference (RNAi) resulted in decreased colonization efficiency and arbuscule richness. Coincidently, genes associated with arbuscule development and degeneration in RNAi roots were also downregulated. In silico analysis showed CCAAT-binding motifs in the promoter regions of downregulated genes, further supporting the involvement of NF-Y complexes in transcriptional regulation of symbiosis. Taken together, this study identifies MtNF-YC6- or MtNF-YC11-containing protein complexes as novel transcriptional regulators of symbiotic program and provides a list of potential downstream target genes. These data will help to further dissect the AMS regulatory network.

Genome-Wide Identification and Characterization of the NF-YA Gene Family and Its Expression in Response to Different Nitrogen Forms in Populus × canescens

The NF-YA gene family is a class of conserved transcription factors that play important roles in plant growth and development and the response to abiotic stress. Poplar is a model organism for studying the rapid growth of woody plants that need to consume many nutrients. However, studies on the response of the NF-YA gene family to nitrogen in woody plants are limited. In this study, we conducted a systematic and comprehensive bioinformatic analysis of the NF-YA gene family based on Populus × canescens genomic data. A total of 13 PcNF-YA genes were identified and mapped to 6 chromosomes. According to the amino acid sequence characteristics and genetic structure of the NF-YA domains, the PcNF-YAs were divided into five clades. Gene duplication analysis revealed five pairs of replicated fragments and one pair of tandem duplicates in 13 PcNF-YA genes. The PcNF-YA gene promoter region is rich in different cis-acting regulatory elements, among which MYB and MYC elements are the most abundant. Among the 13 PcNF-YA genes, 9 contained binding sites for P. × canescens miR169s. In addition, RT-qPCR data from the roots, wood, leaves and bark of P. × canescens showed different spatial expression profiles of PcNF-YA genes. Transcriptome data and RT-qPCR analysis showed that the expression of PcNF-YA genes was altered by treatment with different nitrogen forms. Furthermore, the functions of PcNF-YA genes in transgenic poplar were analyzed, and the potential roles of PcNF-YA genes in the response of poplar roots to different nitrogen forms were revealed, indicating that these genes regulate root growth and development.

Nitrate signaling and use efficiency in crops

Nitrate (NO₃^-) is not only an essential nutrient but also an important signaling molecule for plant growth. Low nitrogen use efficiency (NUE) of crops is causing increasingly serious environmental and ecological problems. Understanding the molecular mechanisms of NO₃^- regulation in crops is crucial for NUE improvement in agriculture. During the last several years, significant progress has been made in understanding the regulation of NO₃^- signaling in crops, and some key NO₃^- signaling factors have been shown to play important roles in NO₃^- utilization. However, no detailed reviews have yet summarized these advances. Here, we focus mainly on recent advances in crop NO₃^- signaling, including short-term signaling, long-term signaling, and the impact of environmental factors. We also review the regulation of crop NUE by crucial genes involved in NO₃^- signaling. This review provides useful information for further research on NO₃^- signaling in crops and a theoretical basis for breeding new crop varieties with high NUE, which has great significance for sustainable agriculture.

Wheat genomic study for genetic improvement of traits in China

Bread wheat (Triticum aestivum L.) is a major crop that feeds 40% of the world's population. Over the past several decades, advances in genomics have led to tremendous achievements in understanding the origin and domestication of wheat, and the genetic basis of agronomically important traits, which promote the breeding of elite varieties. In this review, we focus on progress that has been made in genomic research and genetic improvement of traits such as grain yield, end-use traits, flowering regulation, nutrient use efficiency, and biotic and abiotic stress responses, and various breeding strategies that contributed mainly by Chinese scientists. Functional genomic research in wheat is entering a new era with the availability of multiple reference wheat genome assemblies and the development of cutting-edge technologies such as precise genome editing tools, high-throughput phenotyping platforms, sequencing-based cloning strategies, high-efficiency genetic transformation systems, and speed-breeding facilities. These insights will further extend our understanding of the molecular mechanisms and regulatory networks underlying agronomic traits and facilitate the breeding process, ultimately contributing to more sustainable agriculture in China and throughout the world.

Overexpression of an NF-YC2 gene confers alkali tolerance to transgenic alfalfa (Medicago sativa L.)

Alkaline stress severely limits plant growth and yield worldwide. NF-YC transcription factors (TFs) respond to abiotic stress by activating gene expression. However, the biological function of NF-YC TFs in alfalfa (Medicago sativa L.) is not clear. In our study, an NF-YC2 gene was identified and transgenic plants were obtained by constructing overexpression vector and cotyledon node transformation system in alfalfa. The open reading frame of MsNF-YC2 is 879 bp with 32.4 kDa molecular mass. MsNF-YC2 showed tissue expression specificity and was induced by a variety of abiotic stresses including drought, salt, and alkali stress in alfalfa. Under alkali stress treatment, transgenic plants exhibited higher levels of antioxidant enzyme activities and proline (Pro), correlating with a lower levels of hydrogen peroxide (H₂O₂), superoxide anion (O₂ ^-) compared with wild-type (WT) plants. Transcriptomic results showed that overexpression of MsNF-YC2 regulated the expression of phytohormone signal transduction and photosynthesis-related genes under normal and alkaline stress treatments. These results suggest that the MsNF-YC2 gene plays crucial role enhance alkali adaptation abilities in alfalfa.

GmTDN1 improves wheat yields by inducing dual tolerance to both drought and low-N stress

Genetically enhancing drought tolerance and nutrient use efficacy enables sustainable and stable wheat production in drought-prone areas exposed to water shortages and low soil fertility, due to global warming and declining natural resources. In this study, wheat plants, exhibiting improved drought tolerance and N-use efficacy, were developed by introducing GmTDN1, a gene encoding a DREB-like transcription factor, into two modern winter wheat varieties, cv Shi4185 and Jimai22. Overexpressing GmTDN1 in wheat resulted in significantly improved drought and low-N tolerance under drought and N-deficient conditions in the greenhouse. Field trials conducted at three different locations over a period of 2-3 consecutive years showed that both Shi4185 and Jimai22 GmTDN1 transgenic lines were agronomically superior to wild-type plants, and produced significantly higher yields under both drought and N-deficient conditions. No yield penalties were observed in these transgenic lines under normal well irrigation conditions. Overexpressing GmTDN1 enhanced photosynthetic and osmotic adjustment capacity, antioxidant metabolism, and root mass of wheat plants, compared to those of wild-type plants, by orchestrating the expression of a set of drought stress-related genes as well as the nitrate transporter, NRT2.5. Furthermore, transgenic wheat with overexpressed NRT2.5 can improve drought tolerance and nitrogen (N) absorption, suggesting that improving N absorption in GmTDN1 transgenic wheat may contribute to drought tolerance. These findings may lead to the development of new methodologies with the capacity to simultaneously improve drought tolerance and N-use efficacy in cereal crops to ensure sustainable agriculture and global food security.

Genome Editing Targets for Improving Nutrient Use Efficiency and Nutrient Stress Adaptation

In recent years, the development of RNA-guided genome editing (CRISPR-Cas9 technology) has revolutionized plant genome editing. Under nutrient deficiency conditions, different transcription factors and regulatory gene networks work together to maintain nutrient homeostasis. Improvement in the use efficiency of nitrogen (N), phosphorus (P) and potassium (K) is essential to ensure sustainable yield with enhanced quality and tolerance to stresses. This review outlines potential targets suitable for genome editing for understanding and improving nutrient use (NtUE) efficiency and nutrient stress tolerance. The different genome editing strategies for employing crucial negative and positive regulators are also described. Negative regulators of nutrient signalling are the potential targets for genome editing, that may improve nutrient uptake and stress signalling under resource-poor conditions. The promoter engineering by CRISPR/dead (d) Cas9 (dCas9) cytosine and adenine base editing and prime editing is a successful strategy to generate precise changes. CRISPR/dCas9 system also offers the added advantage of exploiting transcriptional activators/repressors for overexpression of genes of interest in a targeted manner. CRISPR activation (CRISPRa) and CRISPR interference (CRISPRi) are variants of CRISPR in which a dCas9 dependent transcription activation or interference is achieved. dCas9-SunTag system can be employed to engineer targeted gene activation and DNA methylation in plants. The development of nutrient use efficient plants through CRISPR-Cas technology will enhance the pace of genetic improvement for nutrient stress tolerance of crops and improve the sustainability of agriculture.

Improving Crop Nitrogen Use Efficiency Toward Sustainable Green Revolution

The Green Revolution of the 1960s improved crop yields in part through the widespread cultivation of semidwarf plant varieties, which resist lodging but require a high-nitrogen (N) fertilizer input. Because environmentally degrading synthetic fertilizer use underlies current worldwide cereal yields, future agricultural sustainability demands enhanced N use efficiency (NUE). Here, we summarize the current understanding of how plants sense, uptake, and respond to N availability in the model plants that can be used to improve sustainable productivity in agriculture. Recent progress in unlocking the genetic basis of NUE within the broader context of plant systems biology has provided insights into the coordination of plant growth and nutrient assimilation and inspired the implementation of a new breeding strategy to cut fertilizer use in high-yield cereal crops. We conclude that identifying fresh targets for N sensing and response in crops would simultaneously enable improved grain productivity and NUE to launch a new Green Revolution and promote future food security.

Insights to improve the plant nutrient transport by CRISPR/Cas system

We need to improve food production to feed the ever growing world population especially in a changing climate. Nutrient deficiency in soils is one of the primary bottlenecks affecting the crop production both in developed and developing countries. Farmers are forced to apply synthetic fertilizers to improve the crop production to meet the demand. Understanding the mechanism of nutrient transport is helpful to improve the nutrient-use efficiency of crops and promote the sustainable agriculture. Many transporters involved in the acquisition, export and redistribution of nutrients in plants are characterized. In these studies, heterologous systems like yeast and Xenopus were most frequently used to study the transport function of plant nutrient transporters. CRIPSR/Cas system introduced recently has taken central stage for efficient genome editing in diverse organisms including plants. In this review, we discuss the key nutrient transporters involved in the acquisition and redistribution of nutrients from soil. We draw insights on the possible application CRISPR/Cas system for improving the nutrient transport in plants by engineering key residues of nutrient transporters, transcriptional regulation of nutrient transport signals, engineering motifs in promoters and transcription factors. CRISPR-based engineering of plant nutrient transport not only helps to study the process in native plants with conserved regulatory system but also aid to develop non-transgenic crops with better nutrient use-efficiency. This will reduce the application of synthetic fertilizers and promote the sustainable agriculture strengthening the food and nutrient security.

Nitrate/ammonium-responsive microRNA-mRNA regulatory networks affect root system architecture in Populus × canescens

BACKGROUND

Nitrate (NO₃^-) and ammonium (NH₄⁺) are the primary forms of inorganic nitrogen (N) taken up by plant roots, and a lack of these N sources commonly limits plant growth. To better understand how NO₃^- and NH₄⁺ differentially affect root system architecture, we analyzed the expression profiles of microRNAs and their targets in poplar roots treated with three forms of nitrogen S1 (NO₃^-), S2 (NH₄NO₃, normal), and S3 (NH₄⁺) via RNA sequencing.

RESULTS

The results revealed a total of 709 miRNAs. Among them, 57 significantly differentially expressed miRNAs and 28 differentially expressed miRNA-target pairs showed correlated expression profiles in S1 vs. S2. Thirty-six significantly differentially expressed miRNAs and 12 differentially expressed miRNA-target pairs showed correlated expression profiles in S3 vs. S2. In particular, NFYA3, a target of upregulated ptc-miR169i and ptc-miR169b, was downregulated in S1 vs. S2, while NFYA1, a target of upregulated ptc-miR169b, was downregulated in S3 vs. S2 and probably played an important role in the changes in root morphology observed when the poplar plants were treated with different N forms. Furthermore, the miRNA-target pairs ptc-miR169i/b-D6PKL2, ptc-miR393a-5p-AFB2, ptc-miR6445a-NAC14, ptc-miR172d-AP2, csi-miR396a-5p_R + 1_1ss21GA-EBP1, ath-miR396b-5p_R + 1-TPR4, and ptc-miR166a/b/c-ATHB-8 probably contributed to the changes in root morphology observed when poplar plants were treated with different N forms.

CONCLUSIONS

These results demonstrate that differentially expressed miRNAs and their targets play an important role in the regulation of the poplar root system architecture by different N forms.

Genetic Control of Efficient Nitrogen Use for High Yield and Grain Protein Concentration in Wheat: A Review

The increasing global population and the negative effects of nitrogen (N) fertilizers on the environment challenge wheat breeding to maximize yield potential and grain protein concentration (GPC) in an economically and environmentally friendly manner. Understanding the molecular mechanisms for the response of yield components to N availability and assimilates allocation to grains provides the opportunity to increase wheat yield and GPC simultaneously. This review summarized quantitative trait loci/genes which can increase spikes and grain number by enhancing N uptake and assimilation at relative early growth stage, and 1000-grain weight and GPC by increasing post-anthesis N uptake and N allocation to grains.

Barley transcription factor HvNLP2 mediates nitrate signaling and affects nitrogen use efficiency

Plants have evolved complex mechanisms to adapt to the changing nitrogen levels in the environment. In Arabidopsis, more than a dozen nitrate signaling regulatory genes have been characterized, including the NODULE INCEPTION-LIKE PROTEIN (AtNLP) genes, which play essential roles in nitrate signaling. However, whether NLP genes in the Triticeae crops are involved in nitrate regulation and nitrogen use efficiency (NUE) remains unknown. Here, we isolated a barley (Hordeum vulgare L.) mutant, hvnlp2-1, from a TILLING (Targeting Local Lesions IN Genomes) population and constructed two RNAi lines, hvnlp2-2 and hvnlp2-3, to study the function of HvNLP2. The expression of the nitrate-responsive genes was substantially inhibited after nitrate treatment in the hvnlp2 mutants, indicating that HvNLP2 controls nitrate signaling. Nitrate content was significantly higher in the hvnlp2 mutants, which may result from the decreased assimilation of nitrogen caused by reduced nitrate reductase activity and expression of nitrate assimilatory genes. HvNLP2 is localized to the nucleus in the presence of nitrate. Further investigation showed that HvNLP2 binds to and activates the nitrate-responsive cis-elements. Moreover, hvnlp2 exhibited reduced biomass, seed yield, and NUE. Therefore, HvNLP2 controls nitrate signaling and plays an important role in NUE.

Genome-Wide Identification and Characterization of Long Noncoding RNAs in Populus × canescens Roots Treated With Different Nitrogen Fertilizers

Nitrate (NO₃ ^-) and ammonium (NH₄ ⁺) are the primary forms of inorganic nitrogen acquired by plant roots. LncRNAs, as key regulators of gene expression, are a class of non-coding RNAs larger than 200 bp. However, knowledge about the regulatory role of lncRNAs in response to different nitrogen forms remains limited, particularly in woody plants. Here, we performed strand-specific RNA-sequencing of P. × canescens roots under three different nitrogen fertilization treatments. In total, 324 lncRNAs and 6,112 mRNAs were identified as showing significantly differential expression between the NO₃ ^- and NH₄NO₃ treatments. Moreover, 333 lncRNAs and 6,007 mRNAs showed significantly differential expression between the NH₄ ⁺ and NH₄NO₃ treatments. Further analysis suggested that these lncRNAs and mRNAs have different response mechanisms for different nitrogen forms. In addition, functional annotation of cis and trans target mRNAs of differentially expressed lncRNAs indicated that 60 lncRNAs corresponding to 49 differentially expressed cis and trans target mRNAs were involved in plant nitrogen metabolism and amino acid biosynthesis and metabolism. Furthermore, 42 lncRNAs were identified as putative precursors of 63 miRNAs, and 28 differentially expressed lncRNAs were potential endogenous target mimics targeted by 96 miRNAs. Moreover, ceRNA regulation networks were constructed. MSTRG.6097.1, MSTRG.13550.1, MSTRG.2693.1, and MSTRG.12899.1, as hub lncRNAs in the ceRNA networks, are potential candidate lncRNAs for studying the regulatory mechanism in poplar roots under different nitrogen fertilization treatments. The results provide a basis for obtaining insight into the molecular mechanisms of lncRNA responses to different nitrogen forms in woody plants.

Genome-wide screening and identification of nuclear Factor-Y family genes and exploration their function on regulating abiotic and biotic stress in potato (Solanum tuberosum L.)

The Nuclear Factor-Y (NF-Y) transcription factor (TF), which includes three distinct subunits (NF-YA, NF-YB and NF-YC), is known to manipulate various aspects of plant growth, development, and stress responses. Although the NF-Y gene family was well studied in many species, little is known about their functions in potato. In this study, a total of 37 potato NF-Y genes were identified, including 11 StNF-YAs, 20 StNF-YBs, and 6 StNF-YCs. The genetic features of these StNF-Y genes were investigated by comparing their evolutionary relationship, intron/exon organization and motif distribution pattern. Multiple alignments showed that all StNF-Y proteins possessed clearly conserved core regions that were flanked by non-conserved sequences. Gene duplication analysis indicated that nine StNF-Y genes were subjected to tandem duplication and eight StNF-Ys arose from segmental duplication events. Synteny analysis suggested that most StNF-Y genes (33 of 37) were orthologous to potato's close relative tomato (Solanum lycopersicum L.). Tissue-specific expression of the StNF-Y genes suggested their potential roles in controlling potato growth and development. The role of StNF-Ys in regulating potato responses to abiotic stress (ABA, drought and salinity) was also confirmed: twelve StNF-Y genes were up-regulated and another two were down-regulated under different abiotic treatments. In addition, genes responded differently to pathogen challenges, suggesting that StNF-Y genes may play distinct roles under certain biotic stress. In summary, insights into the evolution of NF-Y family members and their functions in potato development and stress responses are provided.

Noncoding-RNA-Mediated Regulation in Response to Macronutrient Stress in Plants

Macronutrient elements including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) are required in relatively large and steady amounts for plant growth and development. Deficient or excessive supply of macronutrients from external environments may trigger a series of plant responses at phenotypic and molecular levels during the entire life cycle. Among the intertwined molecular networks underlying plant responses to macronutrient stress, noncoding RNAs (ncRNAs), mainly microRNAs (miRNAs) and long ncRNAs (lncRNAs), may serve as pivotal regulators for the coordination between nutrient supply and plant demand, while the responsive ncRNA-target module and the interactive mechanism vary among elements and species. Towards a comprehensive identification and functional characterization of nutrient-responsive ncRNAs and their downstream molecules, high-throughput sequencing has produced massive omics data for comparative expression profiling as a first step. In this review, we highlight the recent findings of ncRNA-mediated regulation in response to macronutrient stress, with special emphasis on the large-scale sequencing efforts for screening out candidate nutrient-responsive ncRNAs in plants, and discuss potential improvements in theoretical study to provide better guidance for crop breeding practices.

Meta-QTLs, ortho-MQTLs and candidate genes for nitrogen use efficiency and root system architecture in bread wheat (Triticum aestivum L.)

In wheat, meta-QTLs (MQTLs), ortho-MQTLs, and candidate genes (CGs) were identified for nitrogen use efficiency and root system architecture. For this purpose, 1788 QTLs were available from 24 studies published during 2006-2020. Of these, 1098 QTLs were projected onto the consensus map resulting in 118 MQTLs. The average confidence interval (CI) of MQTLs was reduced up to 8.56 folds in comparison to the average CI of QTLs. Of the 118 MQTLs, 112 were anchored to the physical map of the wheat reference genome. The physical interval of MQTLs ranged from 0.02 to 666.18 Mb with a mean of 94.36 Mb. Eighty-eight of these 112 MQTLs were verified by marker-trait associations (MTAs) identified in published genome-wide association studies (GWAS); the MQTLs that were verified using GWAS also included 9 most robust MQTLs, which are particularly useful for breeders; we call them 'Breeder's QTLs'. Some selected wheat MQTLs were further utilized for the identification of ortho-MQTLs for wheat and maize; 9 such ortho-MQTLs were available. As many as 1991 candidate genes (CGs) were also detected, which included 930 CGs with an expression level of > 2 transcripts per million in relevant organs/tissues. Among the CGs, 97 CGs with functions previously reported as important for the traits under study were selected. Based on homology analysis and expression patterns, 49 orthologues of 35 rice genes were also identified in MQTL regions. The results of the present study may prove useful for the improvement of selection strategy for yield potential, stability, and performance under N-limiting conditions.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01085-0.

Identification and Comprehensive Analysis of the Nuclear Factor-Y Family Genes Reveal Their Multiple Roles in Response to Nutrient Deficiencies in Brassica napus

Nuclear Factor-Y (NF-Y) transcription factors play vital roles in plant abiotic stress response. Here, the NF-Y family in Brassica napus, which is hyper-sensitive to nitrogen (N) deprivation, was comprehensively identified and systematically characterized. A total of 108 NF-Y family members were identified in B. napus and categorized into three subfamilies (38 NF-YA, 46 NF-YB and 24 NF-YC; part of the Arabidopsis NF-YC homologous genes had been lost during B. napus evolution). In addition, the expansion of the NF-Y family in B. napus was driven by whole-genome duplication and segmental duplication. Differed expression patterns of BnaNF-Ys were observed in response to multiple nutrient starvations. Thirty-four genes were regulated only in one nutrient deficient condition. Moreover, more BnaNF-YA genes were differentially expressed under nutrient limited environments compared to the BnaNF-YB and BnaNF-YC subfamilies. Sixteen hub genes responded diversely to N deprivation in five rapeseed tissues. In summary, our results laid a theoretical foundation for the follow-up functional study of the key NF-Y genes in B. napus in regulating nutrient homeostasis, especially N.

Evolutionarily informed machine learning enhances the power of predictive gene-to-phenotype relationships

Inferring phenotypic outcomes from genomic features is both a promise and challenge for systems biology. Using gene expression data to predict phenotypic outcomes, and functionally validating the genes with predictive powers are two challenges we address in this study. We applied an evolutionarily informed machine learning approach to predict phenotypes based on transcriptome responses shared both within and across species. Specifically, we exploited the phenotypic diversity in nitrogen use efficiency and evolutionarily conserved transcriptome responses to nitrogen treatments across Arabidopsis accessions and maize varieties. We demonstrate that using evolutionarily conserved nitrogen responsive genes is a biologically principled approach to reduce the feature dimensionality in machine learning that ultimately improved the predictive power of our gene-to-trait models. Further, we functionally validated seven candidate transcription factors with predictive power for NUE outcomes in Arabidopsis and one in maize. Moreover, application of our evolutionarily informed pipeline to other species including rice and mice models underscores its potential to uncover genes affecting any physiological or clinical traits of interest across biology, agriculture, or medicine.

MicroRNAs: Tiny, powerful players of metal stress responses in plants

Metal contamination of the environment is a widespread problem threatening sustainable and safe crop production. Physio-biochemical and molecular mechanisms of plant responses to metal exposure have been studied to establish the best possible agronomical or biotechnological methods to tackle metal contamination. Metal stress tolerance is regulated by several molecular effectors among which microRNAs are one of the key master regulators of plant growth and stress responses in plants. MicroRNAs are known to coordinate multitude of plant responses to metal stress through antioxidant functions, root growth, hormonal signalling, transcription factors and metal transporters. The present review discusses integrative functions of microRNAs in the regulation of metal stress in plants, which will be useful for engineering stress tolerance traits for improved plant growth and productivity in metal stressed situations.

TaPHT1;9-4B and its transcriptional regulator TaMYB4-7D contribute to phosphate uptake and plant growth in bread wheat

Efficient phosphate (Pi) uptake and utilisation are essential for promoting crop yield. However, the underlying molecular mechanism is still poorly understood in complex crop species such as hexaploid wheat. Here we report that TaPHT1;9-4B and its transcriptional regulator TaMYB4-7D function in Pi acquisition, translocation and plant growth in bread wheat. TaPHT1;9-4B, a high-affinity Pi transporter highly upregulated in roots by Pi deficiency, was identified using quantitative proteomics. Disruption of TaPHT1;9-4B function by BSMV-VIGS or CRISPR editing impaired wheat tolerance to Pi deprivation, whereas transgenic expression of TaPHT1;9-4B in rice improved Pi uptake and plant growth. Using yeast-one-hybrid assay, we isolated TaMYB4-7D, a R2R3 MYB transcription factor that could activate TaPHT1;9-4B expression by binding to its promoter. Silencing TaMYB4-7D decreased TaPHT1;9-4B expression, Pi uptake and plant growth. Four promoter haplotypes were identified for TaPHT1;9-4B, with Hap3 showing significant positive associations with TaPHT1;9-4B transcript level, growth performance and phosphorus (P) content in wheat plants. A functional marker was therefore developed for tagging Hap3. Collectively, our data shed new light on the molecular mechanism controlling Pi acquisition and utilisation in bread wheat. TaPHT1;9-4B and TaMYB4-7D may aid further research towards the development of P efficient crop cultivars.