Phosphoproteomic Profiling Reveals Early Salt-Responsive Mechanisms in Two Foxtail Millet Cultivars

Excess soluble salts in saline soils are harmful to most plants. Understanding the biochemical responses to salts in plants and studying the salt tolerance-associated genetic resources in nature will contribute to the improvement of salt tolerance in crops. As an emerging model crop, foxtail millet (Setaria italica L.) has been regarded as a novel species for stress resistance investigation. Here, the dynamic proteomic and phosphoproteomic profiling of two foxtail millet varieties of An04 and Yugu2 with contrasting salt tolerance characteristics were investigated under salt stress. In total, 10,366 sites representing to 2,862 proteins were detected and quantified. There were 759 and 990 sites corresponding to 484 and 633 proteins identified under salinity in An04 and Yugu2, respectively, and 1,264 and 1,131 phosphorylation sites corresponding to 789 and 731 proteins were identified between these two varieties before and after salt stress, respectively. The differentially-regulated phosphoproteins (DRPPs) were mainly involved in signal transduction, regulation of gene expression, translation, ion transport, and metabolism processes. Yugu2 possessed signal perception and transduction capabilities more rapidly and had a more intense response compared with An04 upon salinity. The sucrose metabolism pathway, in particularly, might play a vital role in salt response in foxtail millet, which not only provides UDP-glucose for the cellulose synthesis and energy production, but also promotes flavonoid related synthesis to enhance the salt tolerance ability. Over-expressing the phospho-mimic sucrose synthase (SuS) (SuSS10D) in soybean roots enhanced salt tolerance compared with over-expressing SuS lines. The knowledge of this research will shed light on elucidating the mechanisms of salt response, and pave the way for crop varieties innovation and cultivation under salinity and stresses.

Comprehensive transcriptional analysis reveals salt stress-regulated key pathways, hub genes and time-specific responsive gene categories in common bermudagrass (Cynodon dactylon (L.) Pers.) roots

Background Despite its good salt-tolerance level, key genes and pathways involved with temporal salt response of common bermudagrass (Cynodon dactylon (L.) Pers.) have not been explored. Therefore, in this study, to understand the underlying regulatory mechanism following the different period of salt exposure, a comprehensive transcriptome analysis of the bermudagrass roots was conducted. Results The transcripts regulated after 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated. Dataset series analysis revealed 16 distinct temporal salt-responsive expression profiles. Enrichment analysis identified potentially important salt responsive genes belonging to specific categories, such as hormonal metabolism, secondary metabolism, misc., cell wall, transcription factors and genes encoded a series of transporters. Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules were significantly positively correlated with the proline content and peroxidase activity and hub genes within these two modules were further determined. Besides, after 1 h of salt treatment, genes belonging to categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis and lipid metabolism were immediately and exclusively up-enriched compared to the subsequent time points, which indicated fast-acting and immediate physiological responses. Genes involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were exclusively up-regulated after 24 h of salt treatment, suggesting a slightly slower reaction of metabolic adjustment. Conclusion Here, we revealed salt-responsive genes belonging to categories that were commonly or differentially expressed in short-term salt stress, suggesting possible adaptive salt response mechanisms in roots. Also, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful future references to explore the molecular mechanisms of bermudagrass.

Comparative transcriptome analyses of maize seedling root responses to salt stress

Salt stress affects crop yield by limiting growth and delaying development. In this study, we constructed 16 transcriptome libraries from maize seedling roots using two maize lines, with contrasting salt tolerance, that were exposed to salt stress for 0, 6, 18 and 36 h. In total, 6,584 differential expression genes (DEGs; 3,669 upregulated, 2,915 downregulated) were induced in the salt-sensitive line and 6,419 DEGs (3,876 upregulated, 2,543 downregulated) were induced in the salt-tolerant line. Several DEGs common to both lines were enriched in the ABA signaling pathway, which was presumed to coordinate the process of maize salt response. A total of 459 DEGs were specifically induced in the salt-tolerant line and represented candidate genes responsible for high salt-tolerance. Expression pattern analysis for these DEGs indicated that the period between 0 and 6 h was a crucial period for the rapid response of the tolerant genes under salt stress. Among these DEGs, several genes, Aux/IAA, SAUR, and CBL-interacting kinase have been reported to regulate salt tolerance. In addition, the transcription factors WRKY, bZIP and MYB acted as regulators in the salt-responsive regulatory network of maize roots. Our findings will contribute to understanding of the mechanism on salt response and provide references for functional gene revelation in plants.

Comprehensive transcriptional analysis reveals salt stress-regulated key pathways, hub genes and time-specific response categories in common bermudagrass (Cynodon dactylon (L.) Pers.) roots

Background: Despite its good salt-tolerance level, key genes and pathways that are involved with temporal salt response of common bermudagrass (Cynodon dactylon (L.) Pers.) have not been explored. Therefore, in this study, to understand the underlying regulatory mechanism following the different period of salt exposure, a comprehensive transcriptome analysis of the bermudagrass roots was conducted.Results: The transcripts regulated after 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated. Dataset series analysis revealed 16 distinct salt-responsive temporal transcripts. Enrichment analysis identified common and distinct stress response themes such as hormonal metabolism, secondary metabolism, misc, cell wall, transcription factors and genes encoded a series of transporters. Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules were significantly positively correlated with the proline content and peroxidase activity and hub genes within these two modules were further determined. Besides, after 1 h of salt treatment, categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis and lipid metabolism were immediately and exclusively up-enriched compared to the subsequent time points, which indicated fast-acting and immediate physiological responses. Other specific categories involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were exclusively up-regulated after 24 h of salt treatment, suggesting a slightly slower reaction of metabolic adjustment.Conclusion: Here, we revealed salt response themes that were commonly or differentially expressed in short-term salt stress, suggesting possible adaptive salt response mechanisms in the roots. Also, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful future references to explore the molecular mechanisms of bermudagrass.

Effect of Zinc Priming on Salt Response of Wheat Seedlings: Relieving or Worsening?

In an attempt to alleviate salt-induced damage, the application of ZnO nanoparticles has been suggested. As the use of these particles has also been associated with phytotoxicity, to better clarify the effect of zinc and its possible mitigation of salt stress, we treated wheat seedlings with ZnO (nanoparticles or their bulk-scale counterparts, amended either in the growth medium, NPs and B, or sprayed on the leaves, SPNPs and SPB) with or without subsequent treatment with salt. Growth, photosynthetic parameters, zinc and ion concentration, and in situ and biochemical determination of oxidative stress in wheat leaves and/or in roots were considered. Both Zn and NaCl significantly inhibited growth and induced severe alterations in root morphology. Oxidative stress and damage decreased or increased under ZnO treatment and in saline conditions depending on the organ and on the size and mode of application of particles. In spite of the higher stress conditions often recorded in treated leaves, neither pigment concentration nor photochemical efficiency were decreased. A large variability in the effects of ZnO treatment/priming on seedling salt response was recorded; however, the presence of a cumulative negative effect of priming and salt stress sometimes observed calls for caution in the use of ZnO in protection from saline stress.

Comprehensive transcriptional analysis reveals salt stress-regulated key pathways, hub genes and time-specific response categories in bermudagrass (Cynodon dactylon) roots

Background: Despite the salt-tolerance quality of bermudagrass (Cynodon dactylon), the key pathways and genes involving in salt response and their temporal response pattern have not been deeply identified. Therefore, a comprehensive transcriptome analysis of the bermudagrass roots was conducted in this study to understand the underlying regulatory mechanism following the different period of salt exposure.Results: The transcripts that commonly and specifically regulated following 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated and analysed. The salt-responsive transcripts were mainly divided into 16 distinct temporal expression profiles by analysing the time series dataset. Enrichment analysis identified groups of stress response themes which are consistent or distinctive with generally observed stress response themes, such as hormonal metabolic (e.g. ABA, Auxin, JA, CTK, ethylene), secondary metabolism (e.g. carotenoid, phenylalanine, flavonoid, phenols, glucosinolates), misc (e.g. UDP glucosyl and glucoronyl transferases, oxidases-copper, peroxidases, plastocyanin-like), lipid metabolism (e.g. ω-3 FA desaturase), cell wall (e.g. cellulose synthesis MUR4, hemicellulose synthesis, cell wall proteins AGPs), transcription factors (e.g. MYB, HB, AP2, EREBP) and genes encoded a series of transporters (e.g. amino, sugars, nitrate, major intrinsic proteins). Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules showed significant positive correlations with proline content and peroxidase activity and hub genes within these two modules were further determined. In addition, after 1 h of salt treatment, categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis, lipid metabolism were immediately and specifically up-enriched compared to the following time points, suggesting a fast-acting and immediate physiological responses. Other specific categories involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were specifically up-regulated after 24 h salt treatment, suggesting longer-term reactions of metabolic adjustment.Conclusion: This study revealed salt response themes that were commonly or differentially expressed in earlier or later salt exposure phases, suggesting adaptive salt response mechanisms in the roots of bermudagrass. In addition, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful references to study the salt response of bermudagrass in the future.