The NAC family transcription factor OsNAP confers abiotic stress response through the ABA pathway

Unlocking the Synergy: ABA Seed Priming Enhances Drought Tolerance in Seedlings of Sweet Sorghum Through ABA-IAA Crosstalk

Abscisic acid (ABA) seed priming impacts plant growth and stress resistance, yet its precise physiological and molecular mechanisms remain elusive. This study explored the role of ABA-priming in enhancing drought acclimation in sweet sorghum (Sorghum bicolor Moench) using physiological assessments and comparative transcriptomics. Under drought stress, ABA-primed seedlings exhibited increased plant height, larger leaves, and higher leaf water content compared to non-primed plants. While drought negatively affected photosynthesis through the regulation of photosystem I and II, ABA-priming improved photosynthesis and WUE by involving in differential expression of photosystem II genes. ABA-priming promoted the accumulation of cuticular wax and cutin, effectively reducing leaf water loss. Drought triggered endogenous ABA production via ABA inactivation genes (UGT, BGLU), while ABA-priming activated auxin (IAA) biosynthesis via YUCCA, enhancing auxin-mediated responses and gibberellic acid (GA) signalling. The synergistic action of ABA and IAA culminated in enhanced drought tolerance. Additionally, ABA-priming and drought stress regulated NAC transcription factors, with SbNAC21-1 emerging as a pivotal transcriptional activator intricately linked to auxin signalling. Overexpression of SbNAC21-1 in Arabidopsis effectively enhanced drought tolerance. These findings offer valuable insights into the intricate mechanisms underpinning the beneficial effects of ABA-priming, ultimately enhancing plant adaptability to environmental stressors.

The NAC transcription factor PagNAC17 enhances salt tolerance in poplar by alleviating photosynthetic inhibition

The NAC transcription factor family is essential for plant growth, development, and stress responses. This study, based on RNA-Seq data from 84K poplar and weighted gene co-expression network analysis (WGCNA), identified PagNAC17 as a key factor in the salt stress response of poplar. A total of 202 PtrNAC TFs were identified and categorized into two major subfamilies, with their conserved motifs, gene structures, and cis-acting elements analyzed. Genes co-expressed with PagNAC17 are involved in energy metabolism, such as photosynthesis (e.g., light absorption and CO2 fixation), oxidative phosphorylation, signal transduction processes, and stress responses (e.g., the glutathione metabolism pathway), suggesting that PagNAC17 may regulate salt tolerance in poplar through these pathways. PagNAC17 is localized in the nucleus, primarily expressed in young leaves with the lowest expression in roots, and has transcriptional activation activity. The expression of PagNAC17 in yeast significantly enhances growth under salt conditions. Likewise, the overexpression of PagNAC17 in 84K poplar also significantly enhances salt tolerance, reducing yellowing, wilting, and oxidative damage. In summary, PagNAC17 is a key salt-tolerance regulator within the poplar NAC gene family. This study provides valuable insights for functional research on the NAC TFs family and offers a promising genetic resource for the salt-tolerance breeding of poplar.

Comparative Transcriptome Analysis of Gene Responses of Salt-Tolerant and Salt-Sensitive Watermelon Cultivars' Roots to Salt Stress

Salt stress, as a significant adverse consequence of global climate change, severely restricts the yield and quality of watermelon. In this study, salt-tolerant cultivar T23 and salt-sensitive cultivar B2 were subjected to a 200 mM NaCl treatment (0 h, 6 h, 24 h, 48 h, and 168 h) at the three-leaf stage, and the adaptation mechanisms of the watermelon roots to salt stress were systematically investigated at the phenotypic, physiological, and gene transcription levels. Phenotypic observations revealed that salt stress inhibited seedling growth, caused leaf curling, and induced root yellowing, with the damage being significantly more severe in B2 than in T23. Compared with B2, the activities of superoxide dismutase (SOD) were increased by -7.13%, 169.15%, 34.95%, 84.87%, and 39.87% under NaCl treatment at 0 h, 6 h, 24 h, 48 h, and 168 h, respectively. Compared to the 0 h NaCl treatment, the proline content in B2 increased by 4.25%, 14.39%, and 110.00% at 24 h, 48 h, and 168 h of NaCl treatment, respectively, while T23 showed increases of 93.74%, 177.55%, and 380.56% at the corresponding time points. The provided physiological data demonstrate that T23 exhibits superior antioxidant and osmoregulatory abilities relative to B2. The transcriptome analysis identified differentially expressed genes (DEGs) between the two cultivars under salt stress, with T23 showing the highest number of DEGs at 6 h, while B2 exhibited a significant increase in DEGs at 168 h. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that metabolic pathways such as plant hormone signal transduction, terpenoid biosynthesis, mitogen-activated protein kinase (MAPK) signaling pathways, transporter activity, and transcription regulator activity play important roles in the salt stress response. Furthermore, yeast overexpression experiments preliminarily validated the critical roles of the tonoplast dicarboxylate transporter gene ClCG01G010280 and the NAC transcription factor gene ClCG05G024110 in salt stress tolerance. This study provides new molecular insights into the salt tolerance mechanism of watermelon and offers potential genetic resources for breeding salt-tolerant varieties.

GWAS and transcriptome analyses unravel ZmGRAS15 regulates drought tolerance and root elongation in maize

BACKGROUND

Drought is a major abiotic stress affecting maize development and growth. Unravelling the molecular mechanisms underlying maize drought tolerance and enhancing the drought tolerance of maize is of great importance. However, due to the complexity of the maize genome and the multiplicity of drought tolerance mechanisms, identifying the genetic effects of drought tolerance remains great challenging.

RESULTS

Using a mixed linear model (MLM) based on 362 maize inbred lines, we identified 40 associated loci and 150 candidate genes associated with survival rates. Concurrently, transcriptome analysis was conducted for five drought - tolerant and five drought - sensitive lines under Well-Watered (WW) and Water-Stressed (WS) conditions. Additionally, through co-expression network analysis (WGCNA), we identified five modules significantly associated with the leaf relative water content (RWC) under drought treatment. By integrating the results of GWAS, DEGs, and WGCNA, four candidate genes (Zm00001d006947, Zm00001d038753, Zm00001d003429 and Zm00001d003553) significantly associated with survival rate were successfully identified. Among them, ZmGRAS15 (Zm00001d003553), a GRAS transcription factor considered as a key hub gene, was selected for further functional validation. The overexpression of ZmGRAS15 in maize could significantly enhance drought tolerance through regulating primary root length at the seedling stage.

CONCLUSION

This study provides valuable information for understanding the genetic basis of drought tolerance and gene resources for maize drought tolerance breeding.

RPT: An integrated root phenotyping toolbox for segmenting and quantifying root system architecture

The dissection of genetic architecture for rice root system is largely dependent on phenotyping techniques, and high-throughput root phenotyping poses a great challenge. In this study, we established a cost-effective root phenotyping platform capable of analysing 1680 root samples within 2 h. To efficiently process a large number of root images, we developed the root phenotyping toolbox (RPT) with an enhanced SegFormer algorithm and used it for root segmentation and root phenotypic traits. Based on this root phenotyping platform and RPT, we screened 18 candidate (quantitative trait loci) QTL regions from 219 rice recombinant inbred lines under drought stress and validated the drought-resistant functions of gene OsIAA8 identified from these QTL regions. This study confirmed that RPT exhibited a great application potential for processing images with various sources and for mining stress-resistance genes of rice cultivars. Our developed root phenotyping platform and RPT software significantly improved high-throughput root phenotyping efficiency, allowing for large-scale root trait analysis, which will promote the genetic architecture improvement of drought-resistant cultivars and crop breeding research in the future.

Metabolic profiling and gene expression analyses shed light on the cold adaptation mechanisms of Saposhnikovia divaricata (Turcz.) Schischk

The northeastern region of China experiences a distinctly cold climate influenced by the Siberian High during the winter months, thus resulting in severe cold weather conditions. Snow cover is prevalent and can persist for several months. This prolonged exposure to low temperatures necessitates specific adaptations in terms of agriculture and plant life, particularly for perennial herbs. Saposhnikovia divaricate (Turcz.) Schischk (SD) is a widely distributed perennial herb in the northeastern and northern provinces of China. However, there is limited documentation on the molecular mechanism through which this plant adapts to cold stress. Therefore, we elucidated the SD response to cold stress by transcriptome and metabolome analysis. Cold stress induced chlorosis and wilting in plants, thus leading to added function of antioxidant enzymes and higher levels of malondialdehyde, proline, soluble sugars. Notably, the differentially expressed genes (DEGs) were primarily related with sugar metabolism, ROS sweep, flavonoid and terpenoid biosynthesis, plant hormone signalling pathways, lipid metabolism, and transcription factors. Additionally, the differentially expressed metabolites (DEMs) mainly included lipids, flavonoids, terpenoid compounds, sugar-related metabolites, alkaloids and other metabolites. Furthermore, integrated analysis revealed coexpression patterns between carbohydrate metabolism-related genes and genes reference flavonoid and terpenoid biosynthesis, along with their corresponding metabolites. Finally, the qPCR results revealed notable over-expression levels of stress-related genes, including those participated in plant hormone signalling pathways (PP2C and AUX), flavonoid biosynthesis (CH3), antioxidant enzymes (AOX and CAT), and sugar-related metabolite metabolism (TPS, SPS, and SS). In conclusion, our findings suggest that cold stress strongly affects plant hormone signalling pathways, ROS scavenging mechanisms, unsaturated fatty acid synthesis and flavonoid and terpenoid biosynthesis in SD. These discoveries provide valuable insights into the impact of cold climates on herbaceous plants.

Gene Pyramiding Strategies for Sink Size and Source Capacity for High-Yield Japonica Rice Breeding

In Japan, high-yielding indica rice cultivars such as 'Habataki', 'Takanari', and 'Hokuriku 193' have been bred, and many genes related to the high-yield traits have been isolated from these and other indica cultivars. Many such genes are expected to be effective in increasing the yield of japonica rice, including those that increase sink size. It has been expected that high-yielding japonica rice could be bred by introducing sink-size genes into the genetic background of japonica cultivars such as 'Koshihikari', which show strong cold tolerance, have good taste characteristics, and fetch a high price. However, the corresponding near-isogenic lines did not necessarily produce high yields when tested in the field. In this review, we summarize information on the major high-yield-related rice genes and discuss pyramiding strategies to further increase the yield of japonica rice. In parallel with increasing sink size, source capacity needs to be increased by increasing photosynthetic rate per unit leaf area (single leaf photosynthesis), improving canopy structure, and increasing translocation capacity during the ripening stage. To implement these strategies, innovative breeding methodologies that efficiently produce the combinations of desired alleles are required.

Overexpression of NAC transcription factors from Eremopyrum triticeum promoted abiotic stress tolerance

Eremopyrum triticeum is a typical spring ephemeral species, which in China mainly distributed in the desert regions of northern Xinjiang, and play an important role in the desert ecosystems. E. triticeum has several adaptive characteristics such as short growth rhythms, high photosynthetic efficiency, high seed production, drought and salt resistance. However, the molecular regulatory mechanism of E. triticeum in responses to abiotic stress resistance is still unknown. In this study, two NAC-like transcription factor-encoding genes, EtNAC1 and EtNAC2, were isolated from E. triticeum. The predicted EtNAC1 and EtNAC2 proteins possess a typical NAC DNA-binding domain at the N-terminal region. The qRT-PCR analysis showed that EtNAC1 and EtNAC2 were highly expressed in mature roots of E. triticeum, and were significantly up-regulated under drought, high salt and abscisic acid (ABA) stresses. Subcellular localization analysis in onion epidermal cells revealed that EtNAC1 and EtNAC2 were located in the nucleus. Expression of EtNAC1 and EtNAC2 in yeast cells improved the survival rate of yeast under low temperature, H2O2, high drought and salt stresses. Overexpression of EtNAC1 and EtNAC2 in Arabidopsis thaliana conferred enhanced tolerance to drought and salt stresses, increased ABA sensitivity, and transgenic plants showed higher proline (Pro) content, but lower malondialdehyde content, lower chlorophyll leaching, lower water loss rate and stomatal aperture (width/length) than WT plants. In conclusion, EtNAC1 and EtNAC2 play important roles in abiotic stress responses of E. triticeum, which might have significant potential in crop molecular breeding for abiotic stress tolerance.

Elucidation of PGPR-responsive OsNAM2 regulates salt tolerance in Arabidopsis by AFP2 and SUS protein interaction

This study investigates the molecular mechanisms underlying salt stress responses in plants, focusing on the regulatory roles of OsNAM2, a gene influenced by the plant growth-promoting rhizobacterium Bacillus amyloliquefaciens (SN13). The study examines how SN13-modulated OsNAM2 enhances salt tolerance in Arabidopsis through physiological, biochemical, and molecular analyses. Overexpression of OsNAM2, especially with SN13 inoculation, improves germination, seedling growth, root length, and biomass under high NaCl concentrations compared to wild-type plants, indicating a synergistic effect. OsNAM2 overexpression enhances relative water content, reduces electrolyte leakage and malondialdehyde accumulation, and increases proline content, suggesting better membrane integrity and stress endurance. Furthermore, SN13 and OsNAM2 overexpression modulates essential metabolic genes involved in glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle, facilitating metabolic adjustments crucial for salt stress adaptation. The interaction of OsNAM2 with SUS, facilitated by SN13, suggests enhanced sucrose metabolism efficiency, providing substrates for protective responses. Additionally, OsNAM2 plays a regulatory role in the ABA signaling pathway through significant protein-protein interactions like with AFP2. This study highlights the intricate interplay between SN13-responsive OsNAM2 and key signaling pathways, suggesting strategies for enhancing crop salt tolerance through targeted genetic and microbial interventions.

Understanding of Plant Salt Tolerance Mechanisms and Application to Molecular Breeding

Soil salinization is a widespread hindrance that endangers agricultural production and ecological security. High salt concentrations in saline soils are primarily caused by osmotic stress, ionic toxicity and oxidative stress, which have a negative impact on plant growth and development. In order to withstand salt stress, plants have developed a series of complicated physiological and molecular mechanisms, encompassing adaptive changes in the structure and function of various plant organs, as well as the intricate signal transduction networks enabling plants to survive in high-salinity environments. This review summarizes the recent advances in salt perception under different tissues, physiological responses and signaling regulations of plant tolerance to salt stress. We also examine the current knowledge of strategies for breeding salt-tolerant plants, including the applications of omics technologies and transgenic approaches, aiming to provide the basis for the cultivation of salt-tolerant crops through molecular breeding. Finally, future research on the application of wild germplasm resources and muti-omics technologies to discover new tolerant genes as well as investigation of crosstalk among plant hormone signaling pathways to uncover plant salt tolerance mechanisms are also discussed in this review.

A NAC transcription factor MNAC3-centered regulatory network negatively modulates rice immunity against blast disease

NAC transcription factors (TFs) are pivotal in plant immunity against diverse pathogens. Here, we report the functional and regulatory network of MNAC3, a novel NAC TF, in rice immunity. MNAC3, a transcriptional activator, negatively modulates rice immunity against blast and bacterial leaf blight diseases and pathogen-associated molecular pattern (PAMP)-triggered immune responses. MNAC3 binds to a CACG cis-element and activates the transcription of immune-negative target genes OsINO80, OsJAZ10, and OsJAZ11. The negative function of MNAC3 in rice immunity depends on its transcription of downstream genes such as OsINO80 and OsJAZ10. MNAC3 interacts with immunity-related OsPP2C41 (a protein phosphatase), ONAC066 (a NAC TF), and OsDjA6 (a DnaJ chaperone). ONAC066 and OsPP2C41 attenuate MNAC3 transcriptional activity, while OsDjA6 promotes it. Phosphorylation of MNAC3 at S163 is critical for its negative functions in rice immunity. OsPP2C41, which plays positive roles in rice blast resistance and chitin-triggered immune responses, dephosphorylates MNAC3, suppressing its transcriptional activity on the target genes OsINO80, OsJAZ10, and OsJAZ11 and promoting the translocation of MNAC3 from nucleus to cytoplasm. These results establish a MNAC3-centered regulatory network in which OsPP2C41 dephosphorylates MNAC3, attenuating its transcriptional activity on downstream immune-negative target genes in rice. Together, these findings deepen our understanding of molecular mechanisms in rice immunity and offer a novel strategy for genetic improvement of rice disease resistance.

A novel NAC transcription factor ZmNAC55 negatively regulates drought stress in Zea mays

Drought stress is a major limit on the maize growth and productivity, and understanding the drought response mechanism is one of the important ways to improve drought resistance in maize. However, more drought-related genes and their regulated mechanisms are still to be reported. Here, we identified a novel NAC transcription factor ZmNAC55 in Zea mays and comprehensively investigated the functions of ZmNAC55 under drought stress. ZmNAC55 belonged to the NAP subfamily. ZmNAC55 had a conserved NAC domain in the N-terminal region and a divergent TAR region in the C-terminal region. ZmNAC55 was a nuclear protein, and ZmNAC55 and its TAR region had the transcriptional activation activity. Furthermore, the expression level of ZmNAC55 in leaves could be highly induced by drought stress. ZmNAC55 overexpression in Arabidopsis conferred the drought-sensitive phenotype with higher water loss, lower survival rate, higher membrane ion leakage, and higher expression levels of some drought-related genes. Meanwhile, ZmNAC55 underexpression in maize enhanced drought tolerance with lower water loss, higher survival rate, lower membrane ion leakage and lower expression levels of some drought-related genes. In addition, ZmNAC55 appeared to be very key in regulating ROS production under drought stress. Moreover, ZmNAC55 could activate ZmHOP3 expression by binding to its promoter. A novel working model of ZmNAC55 under drought stress could be found in maize. Taken together, the NAC transcription factor ZmNAC55 could negatively regulate drought stress via increasing ZmHOP3 expression in maize. ZmNAC55 is a promising candidate for improving drought resistance in maize.

Transcriptional Control of Seed Life: New Insights into the Role of the NAC Family

Transcription factors (TFs) regulate gene expression by binding to specific sequences on DNA through their DNA-binding domain (DBD), a universal process. This update conveys information about the diverse roles of TFs, focusing on the NACs (NAM-ATAF-CUC), in regulating target-gene expression and influencing various aspects of plant biology. NAC TFs appeared before the emergence of land plants. The NAC family constitutes a diverse group of plant-specific TFs found in mosses, conifers, monocots, and eudicots. This update discusses the evolutionary origins of plant NAC genes/proteins from green algae to their crucial roles in plant development and stress response across various plant species. From mosses and lycophytes to various angiosperms, the number of NAC proteins increases significantly, suggesting a gradual evolution from basal streptophytic green algae. NAC TFs play a critical role in enhancing abiotic stress tolerance, with their function conserved in angiosperms. Furthermore, the modular organization of NACs, their dimeric function, and their localization within cellular compartments contribute to their functional versatility and complexity. While most NAC TFs are nuclear-localized and active, a subset is found in other cellular compartments, indicating inactive forms until specific cues trigger their translocation to the nucleus. Additionally, it highlights their involvement in endoplasmic reticulum (ER) stress-induced programmed cell death (PCD) by activating the vacuolar processing enzyme (VPE) gene. Moreover, this update provides a comprehensive overview of the diverse roles of NAC TFs in plants, including their participation in ER stress responses, leaf senescence (LS), and growth and development. Notably, NACs exhibit correlations with various phytohormones (i.e., ABA, GAs, CK, IAA, JA, and SA), and several NAC genes are inducible by them, influencing a broad spectrum of biological processes. The study of the spatiotemporal expression patterns provides insights into when and where specific NAC genes are active, shedding light on their metabolic contributions. Likewise, this review emphasizes the significance of NAC TFs in transcriptional modules, seed reserve accumulation, and regulation of seed dormancy and germination. Overall, it effectively communicates the intricate and essential functions of NAC TFs in plant biology. Finally, from an evolutionary standpoint, a phylogenetic analysis suggests that it is highly probable that the WRKY family is evolutionarily older than the NAC family.

Gene expression analysis of potato drought-responsive genes under drought stress in potato (Solanum tuberosum L.) cultivars

The potato (Solanum tuberosum L.), an important field crop consumed extensively worldwide, is adversely affected by abiotic stress factors especially drought. Therefore, it is vital to understand the genetic mechanism under drought stress to decrease loose of yield and quality . This trial aimed to screen drought-responsive gene expressions of potato and determine the drought-tolerant potato cultivar. The trial pattern is a completely randomized block design (CRBD) with four replications under greenhouse conditions. Four cultivars (Brooke, Orwell, Vr808, Shc909) were irrigated with four different water regimes (control and three stress conditions), and the gene expression levels of 10 potato genes were investigated. The stress treatments as follows: Control = 100% field capacity; slight drought = 75% field capacity; moderate drought = 50% field capacity, and severe drought 25% field capacity. To understand the gene expression under drought stress in potato genotypes, RT-qPCR analysis was performed and results showed that the genes most associated with drought tolerance were the StRD22 gene, MYB domain transcription factor, StERD7, Sucrose Synthase (SuSy), ABC Transporter, and StDHN1. The StHSP100 gene had the lowest genetic expression in all cultivars. Among the cultivars, the Orwell exhibited the highest expression of the StRD22 gene under drought stress. Overall, the cultivar with the highest gene expression was the Vr808, closely followed by the Brooke cultivar. As a result, it was determined that potato cultivars Orwell, Vr808, and Brooke could be used as parents in breeding programs to develop drought tolerant potato cultivars.

Chalkiness and premature controlled by energy homeostasis in OsNAC02 Ko-mutant during vegetative endosperm development

BACKGROUND

Chalkiness is a common phenotype induced by various reasons, such as abiotic stress or the imbalance of starch synthesis and metabolism during the development period. However, the reason mainly for one gene losing its function such as NAC (TFs has a large family in rice) which may cause premature is rarely known to us.

RESULTS

The Ko-Osnac02 mutant demonstrated an obviously early maturation stage compared to the wild type (WT) with 15 days earlier. The result showed that the mature endosperm of Ko-Osnac02 mutant exhibited chalkiness, characterized by white-core and white-belly in mature endosperm. As grain filling rate is a crucial factor in determining the yield and quality of rice (Oryza sativa, ssp. japonica), it's significant that mutant has a lower amylose content (AC) and higher soluble sugar content in the mature endosperm. Interestingly among the top DEGs in the RNA sequencing of N2 (3DAP) and WT seeds revealed that the OsBAM2 (LOC_Os10g32810) expressed significantly high in N2 mutant, which involved in Maltose up-regulated by the starch degradation. As Prediction of Protein interaction showed in the chalky endosperm formation in N2 seeds (3 DAP), seven genes were expressed at a lower-level which should be verified by a heatmap diagrams based on DEGs of N2 versus WT. The Tubulin genes controlling cell cycle are downregulated together with the MCM family genes MCM4 ( ↓), MCM7 ( ↑), which may cause white-core in the early endosperm development. In conclusion, the developing period drastically decreased in the Ko-Osnac02 mutants, which might cause the chalkiness in seeds during the early endosperm development.

CONCLUSIONS

The gene OsNAC02 which controls a great genetic co-network for cell cycle regulation in early development, and KO-Osnac02 mutant shows prematurity and white-core in endosperm.

OsNAC120 balances plant growth and drought tolerance by integrating GA and ABA signaling in rice

The crosstalk between gibberellin (GA) and abscisic acid (ABA) signaling is crucial for balancing plant growth and adaption to environmental stress. Nevertheless, the molecular mechanism of their mutual antagonism still remains to be fully clarified. In this study, we found that knockout of the rice NAC (NAM, ATAF1/2, CUC2) transcription factor gene OsNAC120 inhibits plant growth but enhances drought tolerance, whereas OsNAC120 overexpression produces the opposite results. Exogenous GA can rescue the semi-dwarf phenotype of osnac120 mutants, and further study showed that OsNAC120 promotes GA biosynthesis by transcriptionally activating the GA biosynthetic genes OsGA20ox1 and OsGA20ox3. The DELLA protein SLENDER RICE1 (SLR1) interacts with OsNAC120 and impedes its transactivation ability, and GA treatment can remove the inhibition of transactivation activity caused by SLR1. On the other hand, OsNAC120 negatively regulates rice drought tolerance by repressing ABA-induced stomatal closure. Mechanistic investigation revealed that OsNAC120 inhibits ABA biosynthesis via transcriptional repression of the ABA biosynthetic genes OsNCED3 and OsNCED4. Rice OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 9 (OsSAPK9) physically interacts with OsNAC120 and mediates its phosphorylation, which results in OsNAC120 degradation. ABA treatment accelerates OsNAC120 degradation and reduces its transactivation activity. Together, our findings provide evidence that OsNAC120 plays critical roles in balancing GA-mediated growth and ABA-induced drought tolerance in rice. This research will help us to understand the mechanisms underlying the trade-off between plant growth and stress tolerance and to engineer stress-resistant, high-yielding crops.

The Impact of Salinity on Crop Yields and the Confrontational Behavior of Transcriptional Regulators, Nanoparticles, and Antioxidant Defensive Mechanisms under Stressful Conditions: A Review

One of the most significant environmental challenges to crop growth and yield worldwide is soil salinization. Salinity lowers soil solution water potential, causes ionic disequilibrium and specific ion effects, and increases reactive oxygen species (ROS) buildup, causing several physiological and biochemical issues in plants. Plants have developed biological and molecular methods to combat salt stress. Salt-signaling mechanisms regulated by phytohormones may provide additional defense in salty conditions. That discovery helped identify the molecular pathways that underlie zinc-oxide nanoparticle (ZnO-NP)-based salt tolerance in certain plants. It emphasized the need to study processes like transcriptional regulation that govern plants' many physiological responses to such harsh conditions. ZnO-NPs have shown the capability to reduce salinity stress by working with transcription factors (TFs) like AP2/EREBP, WRKYs, NACs, and bZIPs that are released or triggered to stimulate plant cell osmotic pressure-regulating hormones and chemicals. In addition, ZnO-NPs have been shown to reduce the expression of stress markers such as malondialdehyde (MDA) and hydrogen peroxide (H2O2) while also affecting transcriptional factors. Those systems helped maintain protein integrity, selective permeability, photosynthesis, and other physiological processes in salt-stressed plants. This review examined how salt stress affects crop yield and suggested that ZnO-NPs could reduce plant salinity stress instead of osmolytes and plant hormones.

OsNAC103, a NAC Transcription Factor, Positively Regulates Leaf Senescence and Plant Architecture in Rice

Leaf senescence, the last stage of leaf development, is essential for crop yield by promoting nutrition relocation from senescence leaves to new leaves and seeds. NAC (NAM/ATAF1/ATAF2/CUC2) proteins, one of the plant-specific transcription factors, widely distribute in plants and play important roles in plant growth and development. Here, we identified a new NAC member OsNAC103 and found that it plays critical roles in leaf senescence and plant architecture in rice. OsNAC103 mRNA levels were dramatically induced by leaf senescence as well as different phytohormones such as ABA, MeJA and ACC and abiotic stresses including dark, drought and high salinity. OsNAC103 acts as a transcription factor with nuclear localization signals at the N terminal and a transcriptional activation signal at the C terminal. Overexpression of OsNAC103 promoted leaf senescence while osnac103 mutants delayed leaf senescence under natural condition and dark-induced condition, meanwhile, senescence-associated genes (SAGs) were up-regulated in OsNAC103 overexpression (OsNAC103-OE) lines, indicating that OsNAC103 positively regulates leaf senescence in rice. Moreover, OsNAC103-OE lines exhibited loose plant architecture with larger tiller angles while tiller angles of osnac103 mutants decreased during the vegetative and reproductive growth stages due to the response of shoot gravitropism, suggesting that OsNAC103 can regulate the plant architecture in rice. Taken together, our results reveal that OsNAC103 plays crucial roles in the regulation of leaf senescence and plant architecture in rice.

Molecular Mechanisms and Regulatory Pathways Underlying Drought Stress Response in Rice

Rice is a staple food for 350 million people globally. Its yield thus affects global food security. Drought is a serious environmental factor affecting rice growth. Alleviating the inhibition of drought stress is thus an urgent challenge that should be solved to enhance rice growth and yield. This review details the effects of drought on rice morphology, physiology, biochemistry, and the genes associated with drought stress response, their biological functions, and molecular regulatory pathways. The review further highlights the main future research directions to collectively provide theoretical support and reference for improving drought stress adaptation mechanisms and breeding new drought-resistant rice varieties.

Uncovering the Genomic Regions Associated with Yield Maintenance in Rice Under Drought Stress Using an Integrated Meta-Analysis Approach

The complex trait of yield is controlled by several quantitative trait loci (QTLs). Given the global water deficit issue, the development of rice varieties suitable for non-flooded cultivation holds significant importance in breeding programs. The powerful approach of Meta-QTL (MQTL) analysis can be used for the genetic dissection of complicated quantitative traits. In the current study, a comprehensive MQTL analysis was conducted to identify consistent QTL regions associated with drought tolerance and yield-related traits under water deficit conditions in rice. In total, 1087 QTLs from 134 rice populations, published between 2000 to 2021, were utilized in the analysis. Distinct MQTL analysis of the relevant traits resulted in the identification of 213 stable MQTLs. The confidence interval (CI) for the detected MQTLs was between 0.12 and 19.7 cM. The average CI of the identified MQTLs (4.68 cM) was 2.74 times narrower compared to the average CI of the initial QTLs. Interestingly, 63 MQTLs coincided with SNP peak positions detected by genome-wide association studies for yield and drought tolerance-associated traits under water deficit conditions in rice. Considering the genes located both in the QTL-overview peaks and the SNP peak positions, 19 novel candidate genes were introduced, which are associated with drought response index, plant height, panicle number, biomass, and grain yield. Moreover, an inclusive MQTL analysis was performed on all the traits to obtain "Breeding MQTLs". This analysis resulted in the identification of 96 MQTLs with a CI ranging from 0.01 to 9.0 cM. The mean CI of the obtained MQTLs (2.33 cM) was 4.66 times less than the mean CI of the original QTLs. Thirteen MQTLs fulfilling the criteria of having more than 10 initial QTLs, CI < 1 cM, and an average phenotypic variance explained greater than 10%, were designated as "Breeding MQTLs". These findings hold promise for assisting breeders in enhancing rice yield under drought stress conditions.

Genome-wide analysis of the Tritipyrum NAC gene family and the response of TtNAC477 in salt tolerance

NAC transcription factors are widely distributed in the plant kingdom and play an important role in the response to various abiotic stresses in plant species. Tritipyrum, an octoploid derived from hybridization of Triticum aestivum (AABBDD) and Thinopyrum elongatum (EE), is an important genetic resource for integrating the desirable traits of Th. elongatum into wheat. In this study, we investigated the tissue distribution and expression of Tritipyrum NAC genes in the whole genomes of T. aestivum and Th. elongatum after obtaining their complete genome sequences. Based on phylogenetic relationships, conserved motifs, gene synthesis, evolutionary analysis, and expression patterns, we identified and characterized 732 Tritipyrum NAC genes. These genes were divided into six main groups (A, B, C, D, E, and G) based on phylogenetic relationships and evolutionary studies, with members of these groups sharing the same motif composition. The 732 TtNAC genes are widely distributed across 28 chromosomes and include 110 duplicated genes. Gene synthesis analysis indicated that the NAC gene family may have a common ancestor. Transcriptome data and quantitative polymerase chain reaction (qPCR) expression profiles showed 68 TtNAC genes to be highly expressed in response to various salt stress and recovery treatments. Tel3E01T644900 (TtNAC477) was particularly sensitive to salt stress and belongs to the same clade as the salt tolerance genes ANAC019 and ANAC055 in Arabidopsis. Pearson correlation analysis identified 751 genes that correlated positively with expression of TtNAC477, and these genes are enriched in metabolic activities, cellular processes, stimulus responses, and biological regulation. TtNAC477 was found to be highly expressed in roots, stems, and leaves in response to salt stress, as confirmed by real-time PCR. These findings suggest that TtNAC477 is associated with salt tolerance in plants and might serve as a valuable exogenous gene for enhancing salt tolerance in wheat.

Rice Basic Helix-Loop-Helix 079 (OsbHLH079) Delays Leaf Senescence by Attenuating ABA Signaling

Leaf senescence represents the final phase of leaf development and is characterized by a highly organized degenerative process involving the active translocation of nutrients from senescing leaves to growing tissues or storage organs. To date, a large number of senescence-associated transcription factors (sen-TFs) have been identified that regulate the initiation and progression of leaf senescence. Many of these TFs, including NAC (NAM/ATAF1/2/CUC2), WRKY, and MYB TFs, have been implicated in modulating the expression of downstream senescence-associated genes (SAGs) and chlorophyll degradation genes (CDGs) under the control of phytohormones. However, the involvement of basic helix-loop-helix (bHLH) TFs in leaf senescence has been less investigated. Here, we show that OsbHLH079 delays both natural senescence and dark-induced senescence: Overexpression of OsbHLH079 led to a stay-green phenotype, whereas osbhlh079 knockout mutation displayed accelerated leaf senescence. Similar to other sen-TFs, OsbHLH079 showed a gradual escalation in expression as leaves underwent senescence. During this process, the mRNA levels of SAGs and CDGs remained relatively low in OsbHLH079 overexpressors, but increased sharply in osbhlh079 mutants, suggesting that OsbHLH079 negatively regulates the transcription of SAGs and CDGs under senescence conditions. Additionally, we found that OsbHLH079 delays ABA-induced senescence. Subsequent RT-qPCR and dual-luciferase reporter assays revealed that OsbHLH079 downregulates the expression of ABA signaling genes, such as OsABF2, OsABF4, OsABI5, and OsNAP. Taken together, these results demonstrate that OsbHLH079 functions in delaying leaf yellowing by attenuating the ABA responses.

Gene Cloning and Characterization of Transcription Factor FtNAC10 in Tartary Buckwheat (Fagopyrum tataricum (L.) Gaertn.)

NAC transcription factors play a significant role in plant stress responses. In this study, an NAC transcription factor, with a CDS of 792 bp encoding 263 amino acids, was cloned from Fagopyrum tataricum (L.) Gaertn. (F. tataricum), a minor cereal crop, which is rich in flavonoids and highly stress resistant. The transcription factor was named FtNAC10 (NCBI accession number: MK614506.1) and characterized as a member of the NAP subgroup of NAC transcriptions factors. The gene exhibited a highly conserved N-terminal, encoding about 150 amino acids, and a highly specific C-terminal. The resulting protein was revealed to be hydrophilic, with strong transcriptional activation activity. FtNAC10 expression occurred in various F. tataricum tissues, most noticeably in the root, and was regulated differently under various stress treatments. The over-expression of FtNAC10 in transgenic Arabidopsis thaliana (A. thaliana) seeds inhibited germination, and the presence of FtNAC10 enhanced root elongation under saline and drought stress. According to phylogenetic analysis and previous reports, our experiments indicate that FtNAC10 may regulate the stress response or development of F. tataricum through ABA-signaling pathway, although the mechanism is not yet known. This study provides a reference for further analysis of the regulatory function of FtNAC10 and the mechanism that underlies stress responses in Tartary buckwheat.

A Transcription Factor SlNAC4 Gene of Suaeda liaotungensis Enhances Salt and Drought Tolerance through Regulating ABA Synthesis

The NAC (NAM, ATAF1/2 and CUC2) transcription factors are ubiquitously distributed in plants and play critical roles in the construction of plant organs and abiotic stress response. In this study, we described the cloning of a Suaeda liaotungensis K. NAC transcription factor gene SlNAC4, which contained 1450 bp, coding a 331 amino acid. We found that SlNAC4 was highly expressed in stems of S. liaotungensis, and the expression of SlNAC4 was considerably up-regulated after salt, drought, and ABA treatments. Transcription analysis and subcellular localization demonstrated that the SlNAC4 protein was located both in the nucleus and cytoplasm, and contained a C-terminal transcriptional activator. The SlNAC4 overexpression Arabidopsis lines significantly enhanced the tolerance to salt and drought treatment and displayed obviously increased activity of antioxidant enzymes under salt and drought stress. Additionally, transgenic plants overexpressing SlNAC4 had a significantly higher level of physiological indices. Interestingly, SlNAC4 promoted the expression of ABA metabolism-related genes including AtABA1, AtABA3, AtNCED3, AtAAO3, but inhibited the expression of AtCYP707A3 in overexpression lines. Using a yeast one-hybrid (Y1H) assay, we identified that the SlNAC4 transcription factor could bind to the promoters of those ABA metabolism-related genes. These results indicate that overexpression of SlNAC4 in plants enhances the tolerance to salt and drought stress by regulating ABA metabolism.

SNAC3 Transcription Factor Enhances Arsenic Stress Tolerance and Grain Yield in Rice (Oryza sativa L.) through Regulating Physio-Biochemical Mechanisms, Stress-Responsive Genes, and Cryptochrome 1b

Arsenic (As) is one of the toxic heavy metal pollutants found in the environment. An excess of As poses serious threats to plants and diminishes their growth and productivity. NAC transcription factors revealed a pivotal role in enhancing crops tolerance to different environmental stresses. The present study investigated, for the first time, the functional role of SNAC3 in boosting As stress tolerance and grain productivity in rice (Oryza sativa L.). Two SNAC3-overexpressing (SNAC3-OX) and two SNAC3-RNAi transgenic lines were created and validated. The wild-type and transgenic rice plants were exposed to different As stress levels (0, 25, and 50 µM). The results revealed that SNAC3 overexpression significantly improved rice tolerance to As stress and boosted grain yield traits. Under both levels of As stress (25 and 50 µM), SNAC3-OX rice lines exhibited significantly lower levels of oxidative stress biomarkers and OsCRY1b (cryptochrome 1b) expression, but they revealed increased levels of gas exchange characters, chlorophyll, osmolytes (soluble sugars, proteins, proline, phenols, and flavonoids), antioxidant enzymes (SOD, CAT, APX, and POD), and stress-tolerant genes expression (OsSOD-Cu/Zn, OsCATA, OsCATB, OsAPX2, OsLEA3, OsDREB2B, OsDREB2A, OsSNAC2, and OsSNAC1) in comparison to wild-type plants. By contrast, SNAC3 suppression (RNAi) reduced grain yield components and reversed the aforementioned measured physio-biochemical and molecular traits. Taken together, this study is the first to demonstrate that SNAC3 plays a vital role in boosting As stress resistance and grain productivity in rice through modulating antioxidants, photosynthesis, osmolyte accumulation, and stress-related genes expression, and may be a useful candidate for further genetic enhancement of stress resistance in many crops.

Genome-Wide Identification of NAC Gene Family and Expression Analysis under Abiotic Stresses in Avena sativa

In this study, a total of 177 NAC members were identified in Avena sativa, located on 21 chromosomes. Phylogenetic analysis showed that AsNAC proteins could be divided into seven subfamilies (I-VII), and that proteins in the same subfamily have similar protein motifs. Gene structure analysis found that NAC introns ranged from 1 to 17. Cis-element analysis of the promoter indicated that the gene family may have stress-related elements and growth regulation elements. Through qRT-PCR experiments, we speculated that AsNACs genes can respond to abiotic stresses such as cold, freezing, salt, and saline alkali. This study provides a theoretical basis for further exploring the function of the NAC gene family in A. sativa.

Genome-wide identification, evolution and expression analysis of NAC gene family under salt stress in wild emmer wheat (Triticum dicoccoides. L)

The NAC transcription factor (TF) family is one of the largest plant-specific gene families, playing the vital roles in plant growth and development as well as stress response. Although it has been extensively characterized in many plants, the significance of NAC family in wild emmer wheat is not well understood up to now. Here, a total of 200 NAC transcription factors were identified in wild emmer (TdNACs) through a genome-search method, which were classified into 12 subfamilies based on phylogenetic relationship. And the members in the subfamily shared similar exon-intron structure and conversed domain organization. Collinearity analysis revealed that segmental duplication and polyploidization contributed mainly to the expansion of TdNACs. Furthermore, the genetic variations of TdNACs were investigated using the re-sequencing data and genetic bottleneck has occurred on NAC genes when wild emmer domesticated to cultivated emmer wheat. Finally, the expression patterns of these TdNACs were investigated using RNA-seq data of the salt-tolerant genotype under salt stress to obtain salt-responsive TdNACs, and 10 out of which were further validated using QPCR analysis. This study provided the targets for further functional study of TdNAC genes, and also contributed to mine novel genes for improving the salt tolerance in wheat and other crops.

Genome-wide characterization of the PP2C gene family in peanut (Arachis hypogaea L.) and the identification of candidate genes involved in salinity-stress response

Plant protein phosphatase 2C (PP2C) play important roles in response to salt stress by influencing metabolic processes, hormone levels, growth factors, etc. Members of the PP2C family have been identified in many plant species. However, they are rarely reported in peanut. In this study, 178 PP2C genes were identified in peanut, which were unevenly distributed across the 20 chromosomes, with segmental duplication in 78 gene pairs. AhPP2Cs could be divided into 10 clades (A-J) by phylogenetic analysis. AhPP2Cs had experienced segmental duplications and strong purifying selection pressure. 22 miRNAs from 14 different families were identified, targeting 57 AhPP2C genes. Gene structures and motifs analysis exhibited PP2Cs in subclades AI and AII had high structural and functional similarities. Phosphorylation sites of AhPP2C45/59/134/150/35/121 were predicted in motifs 2 and 4, which located within the catalytic site at the C-terminus. We discovered multiple MYB binding factors and ABA response elements in the promoter regions of the six genes (AhPP2C45/59/134/150/35/121) by cis-elements analysis. GO and KEGG enrichment analysis confirmed AhPP2C-A genes in protein binding, signal transduction, protein modification process response to abiotic stimulus through environmental information processing. Based on RNA-Seq data of 22 peanut tissues, clade A AhPP2Cs showed a varying degree of tissue specificity, of which, AhPP2C35 and AhPP2C121 specifically expressed in seeds, while AhPP2C45/59/134/150 expressed in leaves and roots. qRT-PCR indicated that AhPP2C45 and AhPP2C134 displayed significantly up-regulated expression in response to salt stress. These results indicated that AhPP2C45 and AhPP2C134 could be candidate PP2Cs conferring salt tolerance. These results provide further insights into the peanut PP2C gene family and indicate PP2Cs potentially involved in the response to salt stress, which can now be further investigated in peanut breeding efforts to obtain cultivars with improved salt tolerance.

Comparative transcriptome responses of leaf and root tissues to salt stress in wheat strains with different salinity tolerances

Background: Salinity stress is a major adverse environmental factor that can limit crop yield and restrict normal land use. The selection of salt-tolerant strains and elucidation of the underlying mechanisms by plant breeding scientists are urgently needed to increase agricultural production in arid and semi-arid regions. Results: In this study, we selected the salt-tolerant wheat (Triticum aestivum) strain ST9644 as a model to study differences in expression patterns between salt-tolerant and salt-sensitive strains. High-throughput RNA sequencing resulted in more than 359.10 Gb of clean data from 54 samples, with an average of 6.65 Gb per sample. Compared to the IWGSC reference annotation, we identified 50,096 new genes, 32,923 of which have functional annotations. Comparisons of abundances between salt-tolerant and salt-sensitive strains revealed 3,755, 5,504, and 4,344 genes that were differentially expressed at 0, 6, and 24 h, respectively, in root tissue under salt stress. KEGG pathway analysis of these genes showed that they were enriched for phenylpropanoid biosynthesis (ko00940), cysteine and methionine metabolism (ko00270), and glutathione metabolism (ko00480). We also applied weighted gene co-expression network analysis (WGCNA) analysis to determine the time course of root tissue response to salt stress and found that the acute response lasts >6 h and ends before 12 h. We also identified key alternative splicing factors showing different splicing patterns in salt-sensitive and salt-tolerant strains; however, only few of them were differentially expressed in the two groups. Conclusion: Our results offer a better understanding of wheat salt tolerance and improve wheat breeding.

Role of metabolites in flower development and discovery of compounds controlling flowering time

Flowering is one of the most important physiological processes of plants that ensures continuity of genetic flow from one generation to the next and also maintains food security. Therefore, impact of various climate-related abiotic stresses on flowering have been assessed to evaluate the long-term impact of global climate change. In contrast to the enormous volume of research that has been conducted at the genetic, transcriptional, post-transcriptional, and protein level, much less attention has been paid to understand the role of various metabolites in flower induction and floral organ development during normal growth or in stressed environmental condition. This review article aims at summarizing information on various primary (e.g., carbohydrates, lipids, fatty acid derivatives, protein and amino acids) and secondary metabolites (e.g., polyamines, phenolics, neuro-indoles, phenylpropanoid, flavonoids and terpenes) that have so far been identified either during flower induction or in individual floral organs implying their possible role in organ development. Specialized metabolites responsible for flower colour, scent and shape to support plant-pollinator interaction have been extensively reviewed by many research groups and hence are not considered in this article. Many of the metabolites discussed here may be used as metabolomarkers to identify tolerant crop genotypes. Several agrochemicals have been successfully used to release endodormancy in temperate trees. Along the same line, a strategy that combines metabolite profiling, screening of small-molecule libraries, and structural alteration of selected compounds has been proposed in order to identify novel lead compounds that can regulate flowering time when applied exogenously.

Candidate gene discovery for salt tolerance in rice (Oryza sativa L.) at the germination stage based on genome-wide association study

Salt stress affects rice seed germination and seedling formation, seriously restricting rice production. Screening salt-tolerant rice varieties and analyzing the genetic mechanisms underlying salt tolerance are therefore very important to ensure rice production. In this study, 313 Oryza sativa ssp. japonica germplasm were used to conduct a genome-wide association study (GWAS) using 1% NaCl as a salt stress treatment during germination stage. The germination potential (GP) on different days and the germination index (GI) under salt stress were used as salt tolerance indicators. The results of population structure analysis showed that the 313 germplasm studied could be divided into two subpopulations, consistent with the geographical origins of the materials. There were 52 loci significantly related to salt tolerance during germination, and the phenotypic contribution rate of 29 loci was > 10%. A region on chromosome 11 (17049672-17249672 bp) was repeatedly located, and the candidate gene LOC_Os11g29490, which encodes a plasma membrane ATPase, was identified in this locus. Further haplotype analysis showed the GP of germplasm with different haplotypes at that locus significantly differed under salt stress (p < 0.05), and germplasm carrying Hap2 displayed strong salt tolerance during the germination stage. Two other promising candidate genes for salt tolerance were identified: LOC_Os01g27170 (OsHAK3), which encodes a potassium transporter, and LOC_Os10g42550 (OsITPK5), which encodes an inositol 1, 3, 4-trisphosphate 5/6-kinase. The results of this study provide a theoretical basis for salt-tolerant gene cloning and molecular design breeding in rice.

Identification of the NAC Transcription Factors and Their Function in ABA and Salinity Response in Nelumbo nucifera

Nelumbo nucifera Gaertn. is an important perennial aquatic herb that has high ornamental, edible, medicinal, and economic value, being widely distributed and used in China. The NAC superfamily (NAM, ATAF1/2, CUC2) plays critical roles in plant growth, development, and response to abiotic and biotic stresses. Though there have been a few reports about NAC genes in lotus, systematic analysis is still relatively lacking. The present study aimed to characterize all the NAC genes in the lotus and obtain better insights on the NnNACs in response to salt stress by depending on ABA signaling. Here, 97 NAC genes were identified by searching the whole lotus genome based on the raw HMM models of the conserved NAM domain and NAC domain. They were characterized by bioinformatics analysis and divided into 18 subgroups based on the phylogenetic tree. Cis-element analysis demonstrated that NAC genes are responsive to biotic and abiotic stresses, light, low temperature, and plant hormones. Meanwhile, NAC genes had tissue expression specificity. qRT-PCR analysis indicated that NAC genes could be upregulated or downregulated by NaCl treatment, ABA, and fluoridone. In addition, NAC016, NAC025, and NAC070, whose encoding genes were significantly induced by NaCl and ABA, were located in the nucleus. Further analysis showed the three NAC proteins had transcriptional activation capabilities. The co-expression network analysis reflected that NAC proteins may form complexes with other proteins to play a role together. Our study provides a theoretical basis for further research to be conducted on the regulatory mechanisms of salinity resistance in the lotus.

Bolstered plant tolerance to low temperatures by overexpressing NAC transcription factors: identification of critical variables by meta-analysis

The potential biotechnological application of NAC overexpression has been challenged by meta-analysis, establishing a correlation between the magnitudes of several physiological and biochemical parameters and the enhanced tolerance to cold. Overexpression of various NAC (NAM/ATAF/CUC) transcription factors in different plant systems was shown to confer enhanced tolerance to low temperatures by inducing both common and distinctive stress response pathways. However, lack of consensus on the type of parameters evaluated, their magnitudes, and direction of the responses complicates drawing general conclusions on the effects of NAC expression in plant physiology. We report herein a meta-analysis summarizing the most critical response variables used to study the effect of overexpressing NAC regulators on cold stress tolerance. We found that NAC overexpression affected all of the outcome parameters in stressed plants, and one response in control conditions. Transformed plants displayed an increase of at least 40% in positive responses, while negative outcomes were reduced by at least 30%. The most reported parameters included survival, electrolyte leakage, and malondialdehyde contents, whereas the most sensitive to the treatments were the F_v/F_m parameter, survival, and the activity of catalases. We also explored how different experimental arrangements affected the magnitudes of the responses. NAC-mediated improvements were best observed after severe stress episodes and during brief treatments (ranging from 5 to 24 h), especially in terms of antioxidant activities, accumulation of free proline, and parameters related to membrane integrity. Use of heterologous expression also favored several indicators of plant fitness. Our findings should help both basic and applied research on the influence of NAC expression on enhanced tolerance to cold.

Transcriptome Sequencing and Metabolome Analysis Reveals the Molecular Mechanism of Drought Stress in Millet

As one of the oldest agricultural crops in China, millet (Panicum miliaceum) has powerful drought tolerance. In this study, transcriptome and metabolome analyses of ‘Hequ Red millet’ (HQ) and ‘Yanshu No.10’ (YS10) millet after 6 h of drought stress were performed. Transcriptome characteristics of drought stress in HQ and YS10 were characterized by Pacbio full-length transcriptome sequencing. The pathway analysis of the differentially expressed genes (DEGs) showed that the highly enriched categories were related to starch and sucrose metabolism, pyruvate metabolism, metabolic pathways, and the biosynthesis of secondary metabolites when the two millet varieties were subjected to drought stress. Under drought stress, 245 genes related to energy metabolism were found to show significant changes between the two strains. Further analysis showed that 219 genes related to plant hormone signal transduction also participated in the drought response. In addition, numerous genes involved in anthocyanin metabolism and photosynthesis were confirmed to be related to drought stress, and these genes showed significant differential expression and played an important role in anthocyanin metabolism and photosynthesis. Moreover, we identified 496 transcription factors related to drought stress, which came from 10 different transcription factor families, such as bHLH, C3H, MYB, and WRKY. Further analysis showed that many key genes related to energy metabolism, such as citrate synthase, isocitrate dehydrogenase, and ATP synthase, showed significant upregulation, and most of the structural genes involved in anthocyanin biosynthesis also showed significant upregulation in both strains. Most genes related to plant hormone signal transduction showed upregulated expression, while many JA and SA signaling pathway-related genes were downregulated. Metabolome analysis was performed on ‘Hequ red millet’ (HQ) and ‘Yanshu 10’ (YS10), a total of 2082 differential metabolites (DEMs) were identified. These findings indicate that energy metabolism, anthocyanins, photosynthesis, and plant hormones are closely related to the drought resistance of millet and adapt to adversity by precisely regulating the levels of various molecular pathways.

Ectopic Expression of AeNAC83, a NAC Transcription Factor from Abelmoschus esculentus, Inhibits Growth and Confers Tolerance to Salt Stress in Arabidopsis

NAC transcription factors play crucial roles in plant growth, development and stress responses. Previously, we preliminarily identified that the transcription factor AeNAC83 gene was significantly up-regulated under salt stress in okra (Abelmoschus esculentus). Herein, we cloned the nuclear-localized AeNAC83 from okra and identified its possible role in salt stress response and plant growth. The down-regulation of AeNAC83 caused by virus-induced gene silencing enhanced plant sensitivity to salt stress and increased the biomass accumulation of okra seedlings. Meanwhile, AeNAC83-overexpression Arabidopsis lines improved salt tolerance and exhibited many altered phenotypes, including small rosette, short primary roots, and promoted crown roots and root hairs. RNA-seq showed numerous genes at the transcriptional level that changed significantly in the AeNAC83-overexpression transgenic and the wild Arabidopsis with or without NaCl treatment, respectively. The expression of most phenylpropanoid and flavonoid biosynthesis-related genes was largely induced by salt stress. While genes encoding key proteins involved in photosynthesis were almost declined dramatically in AeNAC83-overexpression transgenic plants, and NaCl treatment further resulted in the down-regulation of these genes. Furthermore, DEGs encoding various plant hormone signal pathways were also identified. These results indicate that AeNAC83 is involved in resistance to salt stress and plant growth.

A meta-analysis of microarray data revealed hub genes and transcription factors involved in drought stress response in rice (Oryza sativa L.)

Although there are various studies attempted to clarify the genetic mechanism of plant response to drought stress that reduces crop yield, a meta-analysis can integrate the results of them to provide a better picture of the issue. Therefore, in this study, several microarray datasets of rice were meta-analysed under drought stress and normal condition using the R packages. Accordingly, differentially expressed genes (meta-DEGs) were identified. The results showed 643 and 677 upregulated and downregulated genes, respectively. The significant common Gene Ontology (GO) terms between the up- and downregulated genes were responses to abiotic stimulus , water deprivation , oxygen-containing compound and abscisic acid . The transcription factors (TF) survey showed that bHLH under drought stress activates up genes 42% more than down genes while bzip Homeodomain activates down genes 54% more than up genes. The hub downregulated genes obtained from this study were mainly related to photosynthesis and the hub upregulated genes were mainly related to stress tolerance which include heat shock proteins (HSPs), late embryogenesis abundant (LEAs), calmodulin-like protein (CML), phosphatase 2C (PP2Cs) and IAA genes. Moreover, this meta-analysis data were compared with other experimental data and the results confirmed the up and down expression of them. Our findings can provide novel insights into the molecular mechanism of rice (Oryza sativa L.) response to drought stress.

N7 -SSPP fusion gene improves salt stress tolerance in transgenic Arabidopsis and soybean through ROS scavenging

Considerable signal crosstalk exists in the regulatory network of senescence and stress response. Numerous senescence-associated genes are also involved in plant stress tolerance. However, the underlying mechanisms and application potential of these genes in stress-tolerant crop breeding remain poorly explored. We found that overexpression of SENESCENCE-SUPPRESSED PROTEIN PHOSPHATASE (SSPP), a negative regulator of leaf senescence, significantly improved plant salt tolerance by increasing reactive oxygen species (ROS) scavenging in both Arabidopsis and soybean. However, overexpression of SSPP severely suppressed normal plant growth, limiting its direct use in agriculture. We previously revealed that the N-terminal 1-14 residues of ACS7 (termed 'N7 ') negatively regulated its protein stability through the ubiquitin/proteasome pathway, and the N7 -mediated protein degradation was suppressed by environmental and senescence signals. To avoid the adverse effects of SSPP, the N7 element was fused to the N-terminus of SSPP. We demonstrated that N7 -SSPP fusion gene effectively rescued SSPP-induced growth suppression but maintained enhanced salt tolerance in Arabidopsis and soybean. Particularly, N7 -SSPP enhanced tolerance to long-term salt stress and increased seed yield in soybean. These results suggest that N7 -SSPP overcomes the disadvantages of SSPP on plant growth inhibition and effectively improves salt tolerance through enhanced ROS scavenging, providing an effective strategy of using posttranslational regulatory element for salt-tolerant crop breeding.

A Transcription Factor SlNAC10 Gene of Suaeda liaotungensis Regulates Proline Synthesis and Enhances Salt and Drought Tolerance

The NAC (NAM, ATAF1/2, and CUC2) transcription factors are one of the largest families of transcription factors in plants and play an important role in plant development and the response to adversity. In this study, we cloned a new NAC gene, SlNAC10, from the halophyte Suaeda liaotungensis K. The gene has a total length of 1584 bp including a complete ORF of 1107 bp that encodes 369 amino acids. The SlNAC10-GFP fusion protein is located in the nucleus and SlNAC10 has a transcription activation structural domain at the C-terminus. We studied the expression characteristics of SlNAC10 and found that it was highest in the leaves of S. liaotungensis and induced by drought, salt, cold, and abscisic acid (ABA). To analyze the function of SlNAC10 in plants, we obtained SlNAC10 transgenic Arabidopsis. The growth characteristics and physiological indicators of transgenic Arabidopsis were measured under salt and drought stress. The transgenic Arabidopsis showed obvious advantages in the root length and survival rate; chlorophyll fluorescence levels; and the antioxidant enzyme superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, and the proline content was higher than that of the wild-type (WT) Arabidopsis, whereas the relative electrolyte leakage and malondialdehyde (MDA) content were lower than those of the wild-type Arabidopsis. We explored the regulatory role of SlNAC10 on proline synthesis-related enzyme genes and found that SlNAC10 binds to the AtP5CS1, AtP5CS2, and AtP5CR promoters and regulates their downstream gene transcription. To sum up, SlNAC10 as a transcription factor improves salt and drought tolerance in plants possibly by regulating proline synthesis.

The miR164a-NAM3 module confers cold tolerance by inducing ethylene production in tomato

Because of a high sensitivity to cold, both the yield and quality of tomato (Solanum lycopersicum L.) are severely restricted by cold stress. The NAC transcription factor (TF) family has been characterized as an important player in plant growth, development, and the stress response, but the role of NAC TFs in cold stress and their interaction with other post-transcriptional regulators such as microRNAs in cold tolerance remains elusive. Here, we demonstrated that SlNAM3, the predicted target of Sl-miR164a/b-5p, improved cold tolerance as indicated by a higher maximum quantum efficiency of photosystem II (Fv/Fm), lower relative electrolyte leakage, and less wilting in SlNAM3-overexpression plants compared to wild-type. Further genetic and molecular confirmation revealed that Sl-miR164a/b-5p functioned upstream of SlNAM3 by inhibiting the expression of the latter, thus playing a negative role in cold tolerance. Interestingly, this role is partially mediated by an ethylene-dependent pathway because either Sl-miR164a/b-5p silencing or SlNAM3 overexpression improved cold tolerance in the transgenic lines by promoting ethylene production. Moreover, silencing of the ethylene synthesis genes, SlACS1A, SlACS1B, SlACO1, and SlACO4, resulted in a significant decrease in cold tolerance. Further experiments demonstrated that NAM3 activates SlACS1A, SlACS1B, SlACO1, and SlACO4 transcription by directly binding to their promoters. Taken together, the present study identified the miR164a-NAM3 module conferring cold tolerance in tomato plants via the direct regulation of SlACS1A, SlACS1B, SlACO1, and SlACO4 expression to induce ethylene synthesis.

NAC Transcription Factor TwNAC01 Positively Regulates Drought Stress Responses in Arabidopsis and Triticale

The NAC transcription factors play important roles in regulating plant growth, development, and senescence, and responding to biotic and abiotic stressors in plants. A novel coding sequence (1,059 bp) was cloned from hexaploid triticale in this study. The putative protein (352 amino acids) encoded by this sequence was over 95% similar to the amino acid sequence of a NAC protein from Aegilops tauschii (XP020161331), and it formed a clade with Ae. tauschii, durum wheat, and barley. The putative protein contained a conserved nature actomyosin (NAM) domain (129 consecutive amino acids) between the 20th and 148th amino acids at the N-terminus and three transcription activation regions at the C-terminus. The novel gene was identified as a triticale NAC gene localized in the nucleus and designated as TwNAC01 (GenBank accession MG736919). The expression levels of TwNAC01 were the highest in roots, followed by leaves and stems when triticale lines were exposed to drought, polyethylene glycol 6,000 (PEG6000), NaCl, cold, methyl jasmonate (MeJA), and abscisic acid (ABA). Transgenic Arabidopsis thaliana overexpressing TwNAC01 had significantly lower leaf water loss rates and longer roots than wild-type (WT) A. thaliana. Virus-induced silencing of the TwNAC01 gene in triticale delayed root development and decreased length of primary root. Under drought stress, leaves of TwNAC01-silenced triticale had higher levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), but lower relative water content (RWC), net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, and transpiration rate than the leaves of the WT. Gene overexpression and silencing experiments suggested that TwNAC01 improves plant stress tolerance by increasing root length, regulating the water content of plant leaves by reducing MDA and H₂O₂ content, and adjusting respiration rate. The results suggest that TwNAC01 is a novel NAC transcription factor gene that can be exploited for triticale and cereal improvement.

Dehydration-Responsive Element Binding Protein 1C, 1E, and 1G Promote Stress Tolerance to Chilling, Heat, Drought, and Salt in Rice

The dehydration-responsive element binding protein 1 (DREB1)/C-repeat-binding factor (CBF) genes are key regulators of cold acclimation and freezing tolerance in the chilling tolerant Arabidopsis thaliana. Here, we investigated the function of three members of the 10 rice DREB1 genes, OsDREB1C, E, and G, in the chilling sensitive rice plants. Their loss of function (LOF) mutants were each more chilling susceptible compared to the wild type, and the LOF mutants of all three genes, dreb1ceg, were more chilling susceptible than any of the single mutants. Strikingly, these mutants were capable of cold acclimation, indicating that these rice DREB1 genes are important for basal chilling tolerance but not cold acclimation. Transcriptome and physiology analyses suggest that the OsDREB1C/E/G genes are involved in reactive oxygen species (ROS) scavenging and cell death regulation under chilling. Furthermore, these three rice DREB1 genes are found to promote tolerance to other abiotic stresses: the OsDREB1C/E/G genes are positive regulators of heat tolerance, OsDREB1C and OsDREB1G are positive regulators of salt tolerance, and OsDREB1G is a positive regulator of drought tolerance. These findings expand our knowledge of the roles of DREB1 proteins in plants, enhance our mechanistic understanding of abiotic stress tolerance and will facilitate the generation of stress-tolerant crop plants.

A Rice R2R3-Type MYB Transcription Factor OsFLP Positively Regulates Drought Stress Response via OsNAC

Abiotic stresses adversely affect plant growth and the yield of crops worldwide. R2R3-MYB transcriptional factors have been found to be vital for plants to confer stress response. In Arabidopsis, FOUR LIPS (FLP, MYB124) and its paralogous MYB88 function redundantly regulated the symmetric division of guard mother cells (GMCs) and abiotic stress response. Here, OsFLP was identified as an R2R3-MYB transcriptional activator and localized in the nucleus. OsFLP was transiently induced by drought, salt stress and abscisic acid (ABA). Overexpression of OsFLP showed enhanced tolerance to drought and salt stresses. The stomatal density in OsFLP-OE plants was not changed, whereas the stomatal closure was sensitive to ABA treatment compared to wild-type plants. In contrast, OsFLP-RNAi plants had abnormal stomata and were sensitive to drought. Moreover, the transcripts of stomatal closure-related genes DST and peroxidase 24 precursor, which are identified as downstream of OsNAC1, were inhibited in OsFLP-RNAi plants. The yeast-one-hybrid assay indicated that OsFLP can specifically bind and positively regulate OsNAC1 and OsNAC6. Meanwhile, stress response genes, such as OsLEA3 and OsDREB2A, were up-regulated in OsFLP-OE plants. These findings suggested that OsFLP positively participates in drought stress, mainly through regulating regulators' transcripts of OsNAC1 and OsNAC6.

In-Depth Proteomic Analysis of the Secondary Dormancy Induction by Hypoxia or High Temperature in Barley Grains

In barley, incubation of primary dormant (D1) grains on water under conditions that do not allow germination, i.e. 30°C in air and 15°C or 30°C in 5% O2, induces a secondary dormancy (D2) expressed as a loss of the ability to germinate at 15°C in air. The aim of this study was to compare the proteome of barley embryos isolated from D1 grains and D2 ones after induction of D2 at 30°C or in hypoxia at 15°C or 30°C. Total soluble proteins were analyzed by 2DE gel-based proteomics, allowing the selection of 130 differentially accumulated proteins (DAPs) among 1,575 detected spots. According to the protein abundance profiles, the DAPs were grouped into six abundance-based similarity clusters. Induction of D2 is mainly characterized by a down-accumulation of proteins belonging to cluster 3 (storage proteins, proteases, alpha-amylase inhibitors and histone deacetylase HD2) and an up-accumulation of proteins belonging to cluster 4 (1-Cys peroxiredoxin, lipoxygenase2 and caleosin). The correlation-based network analysis for each cluster highlighted central protein hub. In addition, most of genes encoding DAPs display high co-expression degree with 19 transcription factors. Finally, this work points out that similar molecular events accompany the modulation of dormancy cycling by both temperature and oxygen, including post-translational, transcriptional and epigenetic regulation.

Inactivating transcription factor OsWRKY5 enhances drought tolerance through abscisic acid signaling pathways

During crop cultivation, water-deficit conditions retard growth, thus reducing crop productivity. Therefore, uncovering the mechanisms behind drought tolerance is a critical task for crop improvement. Here, we show that the rice (Oryza sativa) WRKY transcription factor OsWRKY5 negatively regulates drought tolerance. We determined that OsWRKY5 was mainly expressed in developing leaves at the seedling and heading stages, and that its expression was reduced by drought stress and by treatment with NaCl, mannitol, and abscisic acid (ABA). Notably, the genome-edited loss-of-function alleles oswrky5-2 and oswrky5-3 conferred enhanced drought tolerance, measured as plant growth under water-deficit conditions. Conversely, the overexpression of OsWRKY5 in the activation-tagged line oswrky5-D resulted in higher susceptibility under the same conditions. The loss of OsWRKY5 activity increased sensitivity to ABA, thus promoting ABA-dependent stomatal closure. Transcriptome deep sequencing and reverse transcription quantitative polymerase chain reaction analyses demonstrated that the expression of abiotic stress-related genes including rice MYB2 (OsMYB2) was upregulated in oswrky5 knockout mutants and downregulated in oswrky5-D mutants. Moreover, dual-luciferase, yeast one-hybrid, and chromatin immunoprecipitation assays showed that OsWRKY5 directly binds to the W-box sequences in the promoter region of OsMYB2 and represses OsMYB2 expression, thus downregulating genes downstream of OsMYB2 in the ABA signaling pathways. Our results demonstrate that OsWRKY5 functions as a negative regulator of ABA-induced drought stress tolerance, strongly suggesting that inactivation of OsWRKY5 or manipulation of key OsWRKY5 targets could be useful to improve drought tolerance in rice cultivars.

Genome-Wide Expression Analysis of Root Tips in Contrasting Rice Genotypes Revealed Novel Candidate Genes for Water Stress Adaptation

Root system architecture (RSA) is an important agronomic trait with vital roles in plant productivity under water stress conditions. A deep and branched root system may help plants to avoid water stress by enabling them to acquire more water and nutrient resources. Nevertheless, our knowledge of the genetics and molecular control mechanisms of RSA is still relatively limited. In this study, we analyzed the transcriptome response of root tips to water stress in two well-known genotypes of rice: IR64, a high-yielding lowland genotype, which represents a drought-susceptible and shallow-rooting genotype; and Azucena, a traditional, upland, drought-tolerant and deep-rooting genotype. We collected samples from three zones (Z) of root tip: two consecutive 5 mm sections (Z1 and Z2) and the following next 10 mm section (Z3), which mainly includes meristematic and maturation regions. Our results showed that Z1 of Azucena was enriched for genes involved in cell cycle and division and root growth and development whereas in IR64 root, responses to oxidative stress were strongly enriched. While the expansion of the lateral root system was used as a strategy by both genotypes when facing water shortage, it was more pronounced in Azucena. Our results also suggested that by enhancing meristematic cell wall thickening for insulation purposes as a means of confronting stress, the sensitive IR64 genotype may have reduced its capacity for root elongation to extract water from deeper layers of the soil. Furthermore, several members of gene families such as NAC, AP2/ERF, AUX/IAA, EXPANSIN, WRKY, and MYB emerged as main players in RSA and drought adaptation. We also found that HSP and HSF gene families participated in oxidative stress inhibition in IR64 root tip. Meta-quantitative trait loci (QTL) analysis revealed that 288 differentially expressed genes were colocalized with RSA QTLs previously reported under drought and normal conditions. This finding warrants further research into their possible roles in drought adaptation. Overall, our analyses presented several major molecular differences between Azucena and IR64, which may partly explain their differential root growth responses to water stress. It appears that Azucena avoided water stress through enhancing growth and root exploration to access water, whereas IR64 might mainly rely on cell insulation to maintain water and antioxidant system to withstand stress. We identified a large number of novel RSA and drought associated candidate genes, which should encourage further exploration of their potential to enhance drought adaptation in rice.

A Comparative Transcriptomic Meta-Analysis Revealed Conserved Key Genes and Regulatory Networks Involved in Drought Tolerance in Cereal Crops

Drought affects plant growth and development, causing severe yield losses, especially in cereal crops. The identification of genes involved in drought tolerance is crucial for the development of drought-tolerant crops. The aim of this study was to identify genes that are conserved key players for conferring drought tolerance in cereals. By comparing the transcriptomic changes between tolerant and susceptible genotypes in four Gramineae species, we identified 69 conserved drought tolerant-related (CDT) genes that are potentially involved in the drought tolerance of all of the analysed species. The CDT genes are principally involved in stress response, photosynthesis, chlorophyll biogenesis, secondary metabolism, jasmonic acid signalling, and cellular transport. Twenty CDT genes are not yet characterized and can be novel candidates for drought tolerance. The k-means clustering analysis of expression data highlighted the prominent roles of photosynthesis and leaf senescence-related mechanisms in differentiating the drought response between tolerant and sensitive genotypes. In addition, we identified specific transcription factors that could regulate the expression of photosynthesis and leaf senescence-related genes. Our analysis suggests that the balance between the induction of leaf senescence and maintenance of photosynthesis during drought plays a major role in tolerance. Fine-tuning of CDT gene expression modulation by specific transcription factors can be the key to improving drought tolerance in cereals.

Association Mapping and Functional Analysis of Rice Cold Tolerance QTLs at the Bud Burst Stage

Cold tolerance at the bud burst stage (CTB) is a key trait for direct-seeded rice. Although quantitative trait loci (QTL) affecting CTB in rice have been mapped using traditional linkage mapping and genome-wide association study (GWAS) methods, the underlying genes remain unknown. In this study, we evaluated the CTB phenotype of 339 cultivars in the Rice Diversity Panel II (RDP II) collection. GWAS identified four QTLs associated with CTB (qCTBs), distributed on chromosomes 1-3. Among them, qCTB-1-1 overlaps with Osa-miR319b, a known cold tolerance micro RNA gene. The other three qCTBs have not been reported. In addition, we characterised the candidate gene OsRab11C1 for qCTB-1-2 that encodes a Rab protein belonging to the small GTP-binding protein family. Overexpression of OsRab11C1 significantly reduced CTB, while gene knockout elevated CTB as well as cold tolerance at the seedling stage, suggesting that OsRab11C1 negatively regulates rice cold tolerance. Molecular analysis revealed that OsRab11C1 modulates cold tolerance by suppressing the abscisic acid signalling pathway and proline biosynthesis. Using RDP II and GWAS, we identified four qCTBs that are involved in CTB and determined the function of the candidate gene OsRab11C1 in cold tolerance. Our results demonstrate that OsRab11C1 is a negative regulator of cold tolerance and knocking out of the gene by genome-editing may provide enhanced cold tolerance in rice.

A NAC transcription factor OsNAC3 positively regulates ABA response and salt tolerance in rice

BACKGROUND

NAC (NAM, ATAF and CUC) transcription factors (TFs) play vital roles in plant development and abiotic stress tolerance. Salt stress is one of the most limiting factors for rice growth and production. However, the mechanism underlying salt tolerance in rice is still poorly understood.

RESULTS

In this study, we functionally characterized a rice NAC TF OsNAC3 for its involvement in ABA response and salt tolerance. ABA and NaCl treatment induced OsNAC3 expression in roots. Immunostaining showed that OsNAC3 was localized in all root cells. OsNAC3 knockout decreased rice plants' sensitivity to ABA but increased salt stress sensitivity, while OsNAC3 overexpression showed an opposite effect. Loss of OsNAC3 also induced Na⁺ accumulation in the shoots. Furthermore, qRT-PCR and transcriptomic analysis were performed to identify the key OsNAC3 regulated genes related to ABA response and salt tolerance, such as OsHKT1;4, OsHKT1;5, OsLEA3-1, OsPM-1, OsPP2C68, and OsRAB-21.

CONCLUSIONS

This study shows that rice OsNAC3 is an important regulatory factor in ABA signal response and salt tolerance.

Uncovering the Novel QTLs and Candidate Genes of Salt Tolerance in Rice with Linkage Mapping, RTM-GWAS, and RNA-seq

Salinity is a major abiotic stress that limits plant growth and crop productivity. Indica rice and japonica rice show significant differences in tolerance to abiotic stress, and it is considered a feasible method to breed progeny with stronger tolerance to abiotic stress by crossing indica and japonica rice. We herein developed a high-generation recombinant inbred lines (RILs) from Luohui 9 (indica) X RPY geng (japonica). Based on the high-density bin map of this RILs population, salt tolerance QTLs controlling final survival rates were analyzed by linkage mapping and RTM-GWAS methods. A total of seven QTLs were identified on chromosome 3, 4, 5, 6, and 8. qST-3.1, qST-5.1, qST-6.1, and qST-6.2 were novel salt tolerance QTLs in this study and their function were functionally verified by comparative analysis of parental genotype RILs. The gene aggregation result of these four new QTLs emphasized that the combination of the four QTL synergistic genotypes can significantly improve the salt stress tolerance of rice. By comparing the transcriptomes of the root tissues of the parents' seedlings, at 3 days and 7 days after salt treatment, we then achieved fine mapping of QTLs based on differentially expressed genes (DEGs) identification and DEGs annotations, namely, LOC_Os06g01250 in qST-6.1, LOC_Os06g37300 in qST-6.2, LOC_Os05g14880 in qST-5.1. The homologous genes of these candidate genes were involved in abiotic stress tolerance in different plants. These results indicated that LOC_Os05g14880, LOC_Os06g01250, and LOC_Os06g37300 were the candidate genes of qST-5.1, qST-6.1, and qST-6.2. Our finding provided novel salt tolerance-related QTLs, candidate genes, and several RILs with better tolerance, which will facilitate breeding for improved salt tolerance of rice varieties and promote the exploration tolerance mechanisms of rice salt stress.