The 14-3-3 protein OsGF14f interacts with OsbZIP23 and enhances its activity to confer osmotic stress tolerance in rice

The IbDof2.1-IbABF2 module regulates abscisic acid responses and proline biosynthesis to enhance drought tolerance in sweetpotato

Drought is a major abiotic stress that impairs plant growth and development. Developing drought-tolerant crop varieties is an important goal of breeders. Transcription factors belonging to the DNA-binding with one zinc finger (Dof) family regulate plant stress responses and development. However, the roles and regulatory mechanisms of Dof2.1 members in plant stress tolerance are still unclear. Here, we cloned the IbDof2.1 gene from sweetpotato and found that its overexpression significantly enhanced drought tolerance of sweetpotato, whereas IbDof2.1-RNA interference (RNAi) plants displayed the opposite phenotype. The IbDof2.1-overexpression plants showed increased abscisic acid (ABA) and proline contents and stomatal sensitivity to ABA and decreased H2O2 accumulation. Furthermore, we found that IbDof2.1 interacted with ABA-binding factor 2 (IbABF2) and promoted the expression of the proline biosynthesis gene IbP5CS1 to increase proline content, further activating the reactive oxygen species (ROS) scavenging system. These results suggest that the IbDof2.1-IbABF2 module induces stomatal closure and activates the ROS scavenging system by regulating ABA responses and proline biosynthesis to enhance drought tolerance in sweetpotato. Our findings provide novel insights into the roles and regulatory mechanisms of Dof2.1 in plants.

The 14-3-3 gene AaGRF1 positively regulates cold tolerance in kiwifruit

Low temperatures severely threaten the growth and development of kiwifruit. Research has demonstrated that proteins belonging to the 14-3-3 family play a pivotal regulatory function in the ability of plants to resist stress. However, this specific roles of the genes in kiwifruit cold tolerance remain unclear. It had been identified that β-amylase gene, AaBAM3.1, exhibits a positive regulatory effect on kiwifruit's tolerance to low temperature. In our research, we obtained the Actinidia arguta 14-3-3 gene general regulatory factor 1 (AaGRF1) from yeast one-hybrid (Y1H) screening library of the AaBAM3.1 promoter; the expression level of AaGRF1 was enhanced by low-temperature stress. Subcellular localization, Y1H and dual-LUC assay indicated that the AaGRF1 protein resides within the nucleus and possesses the ability to interact with the AaBAM3.1 promoter. Moreover, we also studied the role of AaGRF1 gene in cold resistance of kiwifruit. When AaGRF1 was overexpressed in kiwifruit, the transgenic plants exhibited enhanced cold tolerance. The level of antioxidants and soluble sugars in these plants were elevated compared to wild-type (WT) lines. RNA-seq of the transgenic and WT lines revealed that AaGRF1 might interact with genes in the 'ascorbate-glutathione' and 'starch and sucrose' pathways, thereby enhancing the cold resistance of kiwifruit. In summary, we hypothesize that the 14-3-3 gene AaGRF1 may positively modulate the cold resistance in kiwifruit by accumulating more antioxidants and soluble sugars.

The 14-3-3 protein CaTFT7 interacts with transcription factor CaHDZ27 to positively regulate pepper immunity against Ralstonia solanacearum

Bacterial wilt, caused by Ralstonia solanacearum, is a devastating disease affecting plants in the Solanaceae family. In our previous study, CaHDZ27 was shown to act crucially in the pepper defense response to R. solanacearum. However, the molecular basis underlying CaHDZ27 function remains unexplored. In this study, we demonstrate that CaHDZ27 is post-translationally regulated by the 14-3-3 protein CaTFT7, which functions as a positive regulator in pepper immunity against R. solanacearum. RT-qPCR analysis revealed that CaTFT7 is transcriptionally induced by R. solanacearum infection. The data from virus-induced gene silencing revealed that CaTFT7 positively affects pepper immunity, which was further confirmed by the data of CaTFT7-overexpressing Nicotiana benthamiana. CaTFT7 interacted with CaHDZ27, thereby promoting the stability of CaHDZ27 and enhancing CaHDZ27 binding to the promoter of cysteine-rich receptor-like protein kinase 5 (CaCRK5), a gene that positively affects pepper defense against R. solanacearum. The above data indicated that CaTFT7 enhanced CaHDZ27 stability and promoted its ability to activate pepper immunity, shedding light on the mechanisms underlying pepper resistance to bacterial wilt.

Deep Neural Network-Mining of Rice Drought-Responsive TF-TAG Modules by a Combinatorial Analysis of ATAC-Seq and RNA-Seq

Drought is a critical risk factor that impacts rice growth and yields. Previous studies have focused on the regulatory roles of individual transcription factors in response to drought stress. However, there is limited understanding of multi-factor stresses gene regulatory networks and their mechanisms of action. In this study, we utilised data from the JASPAR database to compile a comprehensive dataset of transcription factors and their binding sites in rice, Arabidopsis, and barley genomes. We employed the PyTorch framework for machine learning to develop a nine-layer convolutional deep neural network TFBind. Subsequently, we obtained rice RNA-seq and ATAC-seq data related to abiotic stress from the public database. Utilising integrative analysis of WGCNA and ATAC-seq, we effectively identified transcription factors associated with open chromatin regions in response to drought. Interestingly, only 81% of the transcription factors directly bound to the opened genes by testing with TFBind model. By this approach we identified 15 drought-responsive transcription factors corresponding to open chromatin regions of targets, which enriched in the terms related to protein transport, protein allocation, nitrogen compound transport. This approach provides a valuable tool for predicting TF-TAG-opened modules during biological processes.

Genome-wide identification of the bZIP family in Eutrema salsugineum and functional analysis of EsbZIP51 in regulating salt tolerance

The halophyte Eutrema salsugineum is naturally distributed in saline-alkali soil and has been proposed as a model plant for understanding plant salt tolerance. As one of the largest and most diverse TF families, basic leucine zipper motif (bZIP) TFs perform robust functions in plant growth and environmental response, however the generalized information of EsbZIP genes and its regulatory role in salt tolerance has not been systematically studied to date. Here, we identified and characterized the bZIP members in E. salsugineum, the sequence feature and phylogeny of EsbZIPs have been exhaustively described. Through the global detection on the transcriptional pattern of EsbZIPs under salt stress, it was found that EsbZIP51 is potentially involved in the positive regulation of salt response. The transgenic plants with heterologous expression of EsbZIP51 exhibited enhanced salt tolerance, as manifested by the healthier growth phenotype and increased capacity in maintaining ion and ROS homeostasis upon salt stress. DNA affinity purification sequencing revealed that a set of candidate genes targeted by EsbZIP51, and functional validation by dual-LUC assays showed EsbZIP51 can specifically bind to the promoter of EsNHX4 and regulates the gene expression, which is required for the modulation of ion balance under salt stress. Together, this study provides insight into the genomic information of EsbZIPs and uncovers a previously uncharacterized functional genes involved in plant salt tolerance.

OsbZIP23 delays flowering by repressing OsMADS14 expression in rice

Flowering time is a fundamental factor determining the global distribution and final yield of rice (Oryza sativa L.). The initiation of the floral transition process signifies the beginning of the reproductive phase. The florigens Heading Date 3a (Hd3a) and Rice Flowering Locus T 1 (RFT1) combine with GF14 proteins and OsFD-like basic leucine zipper (bZIP) transcription factors to form florigen activation/repressor complexes (FACs/FRCs) that regulate the transition to flowering. We herein report that a bZIP transcription factor (OsbZIP23) functions as a flowering repressor. Transgenic plants overexpressing OsbZIP23 exhibited delayed flowering, which was in contrast to the slightly early flowering of the osbzip23 mutants, under natural short-day and long-day conditions. Molecular and biochemical analyses indicated that OsbZIP23 can bind to the 5' untranslated region of OsMADS14 and suppress expression. Moreover, it delays the floral transition probably by interacting with OsFTL1/Hd3a/RFT1 and 14-3-3 proteins to form FRCs. Our findings have further elucidated the molecular mechanisms regulating the flowering time in rice.

The 14-3-3 protein nt GF14e interacts with CIPK2 and increases low potassium stress in tobacco

Potassium (K+) plays a role in enzyme activation, membrane transport, and osmotic regulation processes. An increase in potassium content can significantly improve the elasticity and combustibility of tobacco and reduce the content of harmful substances. Here, we report that the expression analysis of Nt GF14e, a 14-3-3 gene, increased markedly after low-potassium treatment (LK). Then, chlorophyll content, POD activity and potassium content, were significantly increased in overexpression of Nt GF14e transgenic tobacco lines compared with those in the wild type plants. The net K+ efflux rates were severely lower in the transgenic plants than in the wild type under LK stress. Furthermore, transcriptome analysis identified 5708 upregulated genes and 2787 downregulated genes between Nt GF14e overexpressing transgenic tobacco plants. The expression levels of some potassium-related genes were increased, such as CBL-interacting protein kinase 2 (CIPK2), Nt CIPK23, Nt CIPK25, H+-ATPase isoform 2 a (AHA2a), Nt AHA4a, Stelar K+ outward rectifier 1(SKOR1), and high affinity K+ transporter 5 (HAK5). The result of yeast two-hybrid and luciferase complementation imaging experiments suggested Nt GF14e could interact with CIPK2. Overall, these findings indicate that NtGF14e plays a vital roles in improving tobacco LK tolerance and enhancing potassium nutrition signaling pathways in tobacco plants.

OsPUB75-OsHDA716 mediates deactivation and degradation of OsbZIP46 to negatively regulate drought tolerance in rice

Histone deacetylases (HDACs) play crucial roles in plant stress responses via modification of histone as well as nonhistone proteins; however, how HDAC-mediated deacetylation of nonhistone substrates affects protein functions remains elusive. Here, we report that the reduced potassium dependency3/histone deacetylase1-type histone deacetylase OsHDA716 and plant U-box E3 ubiquitin ligase OsPUB75 form a complex to regulate rice drought response via deactivation and degradation of basic leucine zipper (bZIP) transcription factor OsbZIP46 in rice (Oryza sativa). OsHDA716 decreases abscisic acid (ABA)-induced drought tolerance, and mechanistic investigations showed that OsHDA716 interacts with and deacetylates OsbZIP46, a key regulator in ABA signaling and drought response, thus inhibiting its transcriptional activity. Furthermore, OsHDA716 recruits OsPUB75 to facilitate ubiquitination and degradation of deacetylated OsbZIP46. Therefore, the OsPUB75-OsHDA716 complex exerts double restrictions on the transcriptional activity and protein stability of OsbZIP46, leading to repression of downstream drought-responsive gene expression and consequently resulting in reduced drought tolerance. Conversely, OsbZIP46 acts as an upstream repressor to repress OsHDA716 expression, and therefore OsHDA716 and OsbZIP46 form an antagonistic pair to reciprocally inhibit each other. Genetic evidence showed that OsHDA716 works with OsbZIP46 in a common pathway to antagonistically regulate rice drought response, revealing that plants can fine-tune stress responses by the complex interplay between chromatin regulators and transcription factors. Our findings unveil an acetylation-dependent regulatory mechanism governing protein functions and shed light on the precise coordination of activity and stability of key transcription factors through a combination of different posttranslational modifications.

C2H2 Zinc Finger Protein Family Analysis of Rosa rugosa Identified a Salt-Tolerance Regulator, RrC2H2-8

Rosa rugosa is a representative aromatic species. Wild roses are known for their strong tolerance to highly salty environments, whereas cultivated varieties of roses exhibit lower salt stress tolerance, limiting their development and industrial expansion. Previous studies have shown that C2H2-type zinc finger proteins play a crucial role in plants' resistance to abiotic stresses. In this study, 102 C2H2-type zinc finger genes (RrC2H2s) were identified in R. rugosa via a comprehensive approach. These genes were categorized into three lineages, and their motif constitutions were grouped into four classes. RrC2H2s were distributed across all seven rose chromosomes, with 15 paralogous gene pairs identified within synteny regions. Additionally, 43 RrC2H2s showed differential expression across various tissues under salt stress, with RrC2H2-8 being the only gene consistently repressed in all tissues. Subcellular localization analysis revealed that the RrC2H2-8 protein was localized in the nucleus. The heterologous expression of RrC2H2-8 in Arabidopsis significantly improved its growth under salt stress compared to the wild-type (WT) plants. Furthermore, the malondialdehyde content in the roots of transgenic Arabidopsis was significantly lower than that in the WT, suggesting that RrC2H2-8 enhanced salt tolerance by reducing cellular damage. This study provides a systematic understanding of the RrC2H2 family and identifies RrC2H2-8 as a regulator of salt tolerance, laying a foundation for future research on the mechanisms of salt stress regulation by RrC2H2.

Utilizing machine learning and bioinformatics analysis to identify drought-responsive genes affecting yield in foxtail millet

Drought stress is a major constraint on crop development, potentially causing huge yield losses and threatening global food security. Improving Crop's stress tolerance is usually associated with a yield penalty. One way to balance yield and stress tolerance is modification specific gene by emerging precision genome editing technology. However, our knowledge of yield-related drought-tolerant genes is still limited. Foxtail millet (Setaria italica) has a remarkable tolerance to drought and is considered to be a model C4 crop that is easy to engineer. Here, we have identified 46 drought-responsive candidate genes by performing a machine learning-based transcriptome study on two drought-tolerant and two drought-sensitive foxtail millet cultivars. A total of 12 important drought-responsive genes were screened out by principal component analysis and confirmed experimentally by qPCR. Significantly, by investigating the haplotype of these genes based on 1844 germplasm resources, we found two genes (Seita.5G251300 and Seita.8G036300) exhibiting drought-tolerant haplotypes that possess an apparent advantage in 1000 grain weight and main panicle grain weight without penalty in grain weight per plant. These results demonstrate the potential of Seita.5G251300 and Seita.8G036300 for breeding drought-tolerant high-yielding foxtail millet. It provides important insights for the breeding of drought-tolerant high-yielding crop cultivars through genetic manipulation technology.

OsRHS Negatively Regulates Rice Heat Tolerance at the Flowering Stage by Interacting With the HSP Protein cHSP70-4

Heat stress at the flowering stage significantly impacts rice grain yield, yet the number of identified genes associated with rice heat tolerance at this crucial stage remains limited. This study focuses on elucidating the function of the heat-induced gene reduced heat stress tolerance 1 (OsRHS). Overexpression of OsRHS leads to reduced heat tolerance, while RNAi silencing or knockout of OsRHS enhances heat tolerance without compromising yield, as assessed by the seed setting rate. OsRHS is localized in the cytoplasm and mainly expressed in the glume and anther of spikelet. Moreover, OsRHS was found to interact with the HSP protein cHSP70-4, and the knockout of cHSP70-4 resulted in increased heat tolerance. Complementation assays revealed that the knockout of cHSP70-4 could restore the compromised heat tolerance in OsRHS overexpression plants. Additional investigation reveals that elevated temperatures can amplify the bond between OsRHS and cHSP70-4 within rice. Furthermore, our findings indicate that under heat stress conditions during the flowering stage, OsRHS plays a negative regulatory role in the expression of many stress-related genes. These findings unveil the crucial involvement of OsRHS and cHSP70-4 in modulating heat tolerance in rice and identify novel target genes for enhancing heat resilience during the flowering phase in rice.

Transcriptome dynamics in Artemisia annua provides new insights into cold adaptation and de-adaptation

Plants adapt to cold stress through a tightly regulated process involving metabolic reprogramming and tissue remodeling to enhance tolerance within a short timeframe. However, the precise differences and interconnections among various organs during cold adaptation remain poorly understood. This study employed dynamic transcriptomic and metabolite quantitative analyses to investigate cold adaptation and subsequent de-adaptation in Artemisia annua, a species known for its robust resistance to abiotic stress. Our findings revealed distinct expression patterns in most differentially expressed genes (DEGs) encoding transcription factors and components of the calcium signal transduction pathway within the two organs under cold stress. Notably, the long-distance transport of carbon sources from source organs (leaves) to sink organs (roots) experienced disruption followed by resumption, while nitrogen transport from roots to leaves, primarily in the form of amino acids, exhibited acceleration. These contrasting transport patterns likely contribute to the observed differences in cold response between the two organs. The transcriptomic analysis further indicated that leaves exhibited increased respiration, accumulated anti-stress compounds, and initiated the ICE-CBF-COR signaling pathway earlier than roots. Differential expression of genes associated with cell wall biosynthesis suggests that leaves may undergo cell wall thickening while roots may experience thinning. Moreover, a marked difference was observed in phenylalanine metabolism between the two organs, with leaves favoring lignin production and roots favoring flavonoid synthesis. Additionally, our findings suggest that the circadian rhythm is crucial in integrating temperature fluctuations with the plant's internal rhythms during cold stress and subsequent recovery. Collectively, these results shed light on the coordinated response of different plant organs during cold adaptation, highlighting the importance of inter-organ communication for successful stress tolerance.

Spermidine augments salt stress resilience in rice roots potentially by enhancing OsbZIP73's RNA binding capacity

BACKGROUND

Rice is a staple crop for over half of the global population, but soil salinization poses a significant threat to its production. As a type of polyamine, spermidine (Spd) has been shown to reduce stress-induced damage in plants, but its specific role and mechanism in protecting rice roots under salt stress require further investigation.

RESULTS

This study suggested spermidine (Spd) mitigates salt stress on rice root growth by enhancing antioxidant enzyme activity and reducing peroxide levels. Transcriptomic analysis showed that salt stress caused 333 genes to be upregulated and 1,765 to be downregulated. However, adding Spd during salt treatment significantly altered this pattern: 2,298 genes were upregulated and 844 were downregulated, which indicated Spd reverses some transcriptional changes caused by salt stress. KEGG pathway analysis suggested that Spd influenced key signaling pathways, including MAPK signaling, plant hormone signal transduction, and phenylalanine metabolism. Additionally, the bZIP transcription factor OsbZIP73 was upregulated after Spd treatment, which is confirmed by Western blot. Further insights into the interaction between OsbZIP73 and Spd were gained through fluorescence polarization experiments, showing that Spd enhances protein OsbZIP73's affinity for RNA. Functional enrichment analyses revealed that OsPYL1, OsSPARK1, and various SAUR family genes involved in Spd-affected pathways. The presence of G/A/C-box elements in these genes suggests they are potential targets for OsbZIP73.

CONCLUSIONS

Our findings suggest a strategy of using spermidine as a chemical alleviator for salt stress and provide insights into the regulatory function of OsbZIP73 in mitigating salt stress in rice roots.

The key pathways for drought tolerance in Cerasus humilis were unveiled through transcriptome analysis

Drought stress exerts a significant impact on the growth, development, and yield of fruit trees. Cerasus humilis is an endemic drought-resistant fruit tree in northern China. To elucidate the underlying mechanism of drought resistance in C. humilis, comprehensive physiological measurements and transcriptome analysis were conducted on the leaves of C. humilis subjected to 15- or 22-days of drought stress. We identified multiple GO terms and KEGG pathways associated with the drought stress response by performing GO and KEGG analysis on DEGs. Furthermore, through the prediction of transcription factors (TFs) and analysis of their expression levels, we observed differential expression patterns among most members of stress-responsive TF families as the duration of drought stress increased. WGCNA analysis was performed on the transcriptome to identify gene cluster modules that exhibited a strong correlation with the durations of drought. Subsequently, these modules underwent GO and KEGG enrichment analyses. The study revealed that the TF-mediated lignin biosynthesis pathway, along with the plant hormone signal transduction pathway, played a prominent role in responding to drought stress of C. humilis. Gene profiling analysis, qRT-PCR, and determination of phytohormone and lignin contents further supported this hypothesis. The hierarchical gene regulatory network was finally constructed based on DEGs from the aforementioned key enriched pathways to predict the gene regulatory mechanisms in response to stress for C. humilis. The findings from this study provide valuable insights into how C. humilis copes with drought stress while analyzing crucial gene pathways associated with its resistance from a TF perspective. This research is significant for the genetic breeding of economic forests.

Molecular evolution and interaction of 14-3-3 proteins with H+-ATPases in plant abiotic stresses

Environmental stresses severely affect plant growth and crop productivity. Regulated by 14-3-3 proteins (14-3-3s), H+-ATPases (AHAs) are important proton pumps that can induce diverse secondary transport via channels and co-transporters for the abiotic stress response of plants. Many studies demonstrated the roles of 14-3-3s and AHAs in coordinating the processes of plant growth, phytohormone signaling, and stress responses. However, the molecular evolution of 14-3-3s and AHAs has not been summarized in parallel with evolutionary insights across multiple plant species. Here, we comprehensively review the roles of 14-3-3s and AHAs in cell signaling to enhance plant responses to diverse environmental stresses. We analyzed the molecular evolution of key proteins and functional domains that are associated with 14-3-3s and AHAs in plant growth and hormone signaling. The results revealed evolution, duplication, contraction, and expansion of 14-3-3s and AHAs in green plants. We also discussed the stress-specific expression of those 14-3-3and AHA genes in a eudicotyledon (Arabidopsis thaliana), a monocotyledon (Hordeum vulgare), and a moss (Physcomitrium patens) under abiotic stresses. We propose that 14-3-3s and AHAs respond to abiotic stresses through many important targets and signaling components of phytohormones, which could be promising to improve plant tolerance to single or multiple environmental stresses.

The 14-3-3 Protein BdGF14a Increases the Transcriptional Regulation Activity of BdbZIP62 to Confer Drought and Salt Resistance in Tobacco

BdGF14a, a 14-3-3 gene from Brachypodium distachyon, induced by salt, H2O2, and abscisic acid (ABA), improved tolerance to drought and salt in tobacco, with a higher survival rate and longer roots under these stresses. Additionally, physiological index analyses showed that the heterologous expression of BdGF14a induced higher expression levels of antioxidant enzymes and their activities, leading to lighter DAB and NBT staining, denoting decreased H2O2 content. Additionally, the lower MDA content and ion leakage indicated enhanced cell membrane stability. Moreover, exogenous ABA resulted in shorter roots and a lower stomatal aperture in BdGF14a transgenic plants. BdGF14a interacted with NtABF2 and regulated the expression of stress-related genes. However, adding an ABA biosynthesis inhibitor suppressed most of these changes. Furthermore, similar salt and drought resistance phenotypes and physiological indicators were characterized in tobacco plants expressing BdbZIP62, an ABRE/ABF that interacts with BdGF14a. And Y1H and LUC assays showed that BdGF14a could enhance the transcription regulation activity of NtABF2 and BdbZIP62, targeting NtNECD1 by binding to the ABRE cis-element. Thus, BdGF14a confers resistance to drought and salinity through interaction with BdbZIP62 and enhances its transcriptional regulation activity via an ABA-mediated signaling pathway. Therefore, this work offers novel target genes for breeding salt- and drought-tolerant plants.

An LcMYB111-LcHY5 Module Differentially Activates an LcFLS Promoter in Different Litchi Cultivars

Flavonol synthase (FLS) is the crucial enzyme of the flavonol biosynthetic pathways, and its expression is tightly regulated in plants. In our previous study, two alleles of LcFLS,LcFLS-A and LcFLS-B, have been identified in litchi, with extremely early-maturing (EEM) cultivars only harboring LcFLS-A, while middle-to-late-maturing (MLM) cultivars only harbor LcFLS-B. Here, we overexpressed both LcFLS alleles in tobacco, and transgenic tobacco produced lighter-pink flowers and showed increased flavonol levels while it decreased anthocyanin levels compared to WT. Two allelic promoters of LcFLS were identified, with EEM cultivars only harboring proLcFLS-A, while MLM cultivars only harbor proLcFLS-B. One positive and three negative R2R3-MYB transcription regulators of LcFLS expression were identified, among which only positive regulator LcMYB111 showed a consistent expression pattern with LcFLS, which both have higher expression in EEM than that of MLM cultivars. LcMYB111 were further confirmed to specifically activate proLcFLS-A with MYB-binding element (MBE) while being unable to activate proLcFLS-B with mutated MBE (MBEm). LcHY5 were also identified and can interact with LcMYB111 to promote LcFLS expression. Our study elucidates the function of LcFLS and its differential regulation in different litchi cultivars for the first time.