Proteome-wide lysine acetylation profiling to investigate the involvement of histone deacetylase HDA5 in the salt stress response of Arabidopsis leaves

OsHDAC1 deacetylates the aldehyde dehydrogenase OsALDH2B1, repressing OsGR3 and decreasing salt tolerance in rice

Salt stress poses a significant challenge to the growth and productivity of rice (Oryza sativa L.). Histone deacetylases (HDACs) play a vital role in modulating responses to various abiotic stresses. However, how OsHDAC1 responds to salt stress remains largely unknown. Here, we report that OsHDAC1 decreases salt tolerance in rice through posttranslational modification of metabolic enzymes. Specifically, the rice OsHDAC1 RNAi lines exhibited enhanced resilience to salt stress, while plants overexpressing OsHDAC1 were notably more sensitive. OsHDAC1 interacts with the aldehyde dehydrogenase (ALDH) OsALDH2B1 and deacetylates it at K311 and K531, triggering ubiquitin-proteasome-mediated degradation of OsALDH2B1. OsALDH2B1 can directly target OsGR3, which encodes a type of glutathione reductase critical for reactive oxygen species scavenging. Compared with wild-type plants, OsALDH2B1-overexpressing plants exhibited higher OsGR3 expression levels and increased salt resistance, whereas OsALDH2B1 RNAi lines showed reduced OsGR3 expression and lower salt resistance. Collectively, our data suggest that salt stress downregulates OsHDAC1, resulting in an increase in the acetylation level of OsALDH2B1, which in turn stabilizes OsALDH2B1 and promotes its activity in the regulation of OsGR3 transcription. This OsHDAC1/OsALDH2B1/OsGR3 regulatory module represents an alternative pathway for governing salt stress adaptation in rice.

DOG1 controls dormancy independently of ABA core signaling kinases regulation by preventing AFP dephosphorylation through AHG1

Seed dormancy determines germination timing, influencing seed plant adaptation and overall fitness. DELAY OF GERMINATION 1 (DOG1) is a conserved central regulator of dormancy cooperating with the phytohormone abscisic acid (ABA) through negative regulation of ABA HYPERSENSITIVE GERMINATION (AHG) 1 and AHG3 phosphatases. The current molecular mechanism of DOG1 signaling proposes it regulates the activation of central ABA-related SnRK2 kinases. Here, we unveil DOG1's functional autonomy from the regulation of ABA core signaling components and unravel its pivotal control over the activation of ABSCISIC ACID INSENSITIVE FIVE BINDING PROTEINs (AFPs). Our data revealed a molecular relay in which AFPs' genuine activation by AHG1 is contained by DOG1 to prevent the breakdown of maturation-imposed ABA responses independently of ABA-related kinase activation status. This work offers a molecular understanding of how plants fine-tune germination timing, while preserving seed responsiveness to adverse environmental cues, and thus represents a milestone in the realm of conservation and breeding programs.

SIRT2-mediated deacetylation of glutathione transferase alleviates oxidative damage and increases the heat tolerance of Pleurotus ostreatus

High-temperature stress (HS) severely threatens agricultural production. Pleurotus ostreatus is cultivated in many parts of the world, and its growth is strongly affected by HS. We previously reported that metabolic rearrangement occurred in HS, but the gene expression levels of several key enzymes remained unchanged. Therefore, in this study, we investigated the contribution of posttranslational modifications of proteins to HS resistance in P. ostreatus. We found that the level of acetylation of P. ostreatus decreased under short-term HS treatment and increased as the duration of HS treatment increased. Acetylation omics revealed that almost all metabolic enzymes were acetylated. We found that deacetylation under HS can improve the growth recovery ability of mycelia, the activity of matrix-degrading enzyme, and the contents of antioxidants, such as nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH), but can decreased H2O2 levels. In vitro acetylation experiments and point mutations revealed that the deacetylase SIRT2 increased the activity of glutathione transferases (GSTs) by deacetylating GST1 66K, GST2 206K, and GST2 233K. Together, SIRT2 is activated by short-term HS and improves its antioxidant activity by deacetylating GSTs, thereby improving the resistance of P. ostreatus to HS. In this study, we identified new non-histone substrate proteins and new lysine acetylation sites of SIRT2 under HS. We also discovered the role of non-histone acetylation in the adaptation of organisms to HS.

Histone deacetylase GhHDA5 negatively regulates Verticillium wilt resistance in cotton

Verticillium wilt (VW) caused by Verticillium dahliae (V. dahliae) is one of the most destructive diseases in cotton (Gossypium spp.). Histone acetylation plays critical roles in plant development and adaptive responses to biotic and abiotic stresses. However, the relevance of histone acetylation in cotton VW resistance remains largely unclear. Here, we identified histone deacetylase 5 (GhHDA5) from upland cotton (Gossypium hirsutum L.), as a negative regulator of VW resistance. GhHDA5 expression was responsive to V. dahliae infection. Silencing GhHDA5 in upland cotton led to improved resistance to V. dahliae, while heterologous expression of GhHDA5 in Arabidopsis (Arabidopsis thaliana) compromised V. dahliae tolerance. GhHDA5 repressed the expression of several lignin biosynthesis-related genes, such as 4-coumarate:CoA ligase gene Gh4CL3 and ferulate 5-hydroxylase gene GhF5H, through reducing the acetylation level of histone H3 lysine 9 and 14 (H3K9K14ac) at their promoter regions, thereby resulting in an increased deposition of lignin, especially S monomers, in the GhHDA5-silenced cotton plants. The silencing of GhF5H impaired cotton VW tolerance. Additionally, the silencing of GhHDA5 also promoted the production of reactive oxygen species (ROS), elevated the expression of several pathogenesis-related genes (PRs), and altered the content and signaling of the phytohormones salicylic acid (SA), jasmonic acid (JA), and strigolactones (SLs) after V. dahliae infection. Taken together, our findings suggest that GhHDA5 negatively regulates cotton VW resistance through modulating disease-induced lignification and the ROS- and phytohormone-mediated defense response.

Genome-wide mapping of main histone modifications and coordination regulation of metabolic genes under salt stress in pea (Pisum sativum L)

Pea occupy a key position in modern biogenetics, playing multifaceted roles as food, vegetable, fodder, and green manure. However, due to the complex nature of its genome and the prolonged unveiling of high-quality genetic maps, research into the molecular mechanisms underlying pea development and stress responses has been significantly delayed. Furthermore, the exploration of its epigenetic modification profiles and associated regulatory mechanisms remains uncharted. This research conducted a comprehensive investigation of four specific histone marks, namely H3K4me3, H3K27me3, H3K9ac, and H3K9me2, and the transcriptome in pea under normal conditions, and established a global map of genome-wide regulatory elements, chromatin states, and dynamics based on these major modifications. Our analysis identified epigenomic signals across ~82.6% of the genome. Each modification exhibits distinct enrichment patterns: H3K4me3 is predominantly associated with the gibberellin response pathway, H3K27me3 is primarily associated with auxin and ethylene responses, and H3K9ac is primarily associated with negative regulatory stimulus responses. We also identified a novel bivalent chromatin state (H3K9ac-H3K27me3) in pea, which is related to their development and stress response. Additionally, we unveil that these histone modifications synergistically regulate metabolic-related genes, influencing metabolite production under salt stress conditions. Our findings offer a panoramic view of the major histone modifications in pea, elucidate their interplay, and highlight their transcriptional regulatory roles during salt stress.

Proteomics: An Essential Tool to Study Plant-Specialized Metabolism

Plants are a valuable source of specialized metabolites that provide a plethora of therapeutic applications. They are natural defenses that plants use to adapt and respond to their changing environment. Decoding their biosynthetic pathways and understanding how specialized plant metabolites (SPMs) respond to biotic or abiotic stress will provide vital knowledge for plant biology research and its application for the future sustainable production of many SPMs of interest. Here, we focus on the proteomic approaches and strategies that help with the study of plant-specialized metabolism, including the: (i) discovery of key enzymes and the clarification of their biosynthetic pathways; (ii) study of the interconnection of both primary (providers of carbon and energy for SPM production) and specialized (secondary) metabolism; (iii) study of plant responses to biotic and abiotic stress; (iv) study of the regulatory mechanisms that direct their biosynthetic pathways. Proteomics, as exemplified in this review by the many studies performed to date, is a powerful tool that forms part of omics-driven research. The proteomes analysis provides an additional unique level of information, which is absent from any other omics studies. Thus, an integrative analysis, considered versus a single omics analysis, moves us more closely toward a closer interpretation of real cellular processes. Finally, this work highlights advanced proteomic technologies with immediate applications in the field.

Functions and mechanisms of non-histone protein acetylation in plants

Lysine acetylation, an evolutionarily conserved post-translational protein modification, is reversibly catalyzed by lysine acetyltransferases and lysine deacetylases. Lysine acetylation, which was first discovered on histones, mainly functions to configure the structure of chromatin and regulate gene transcriptional activity. Over the past decade, with advances in high-resolution mass spectrometry, a vast and growing number of non-histone proteins modified by acetylation in various plant species have been identified. Lysine acetylation of non-histone proteins is widely involved in regulating biological processes in plants such as photosynthesis, energy metabolism, hormone signal transduction and stress responses. Moreover, in plants, lysine acetylation plays crucial roles in regulating enzyme activity, protein stability, protein interaction and subcellular localization. This review summarizes recent progress in our understanding of the biological functions and mechanisms of non-histone protein acetylation in plants. Research prospects in this field are also noted.

Advances in understanding the roles of plant HAT and HDAC in non-histone protein acetylation and deacetylation

MAIN CONCLUSION

This review focuses on HATs and HDACs that modify non-histone proteins, summarizes functional mechanisms of non-histone acetylation as well as the roles of HATs and HDACs in rice and Arabidopsis. The growth and development of plants, as well as their responses to biotic and abiotic stresses, are governed by intricate gene and protein regulatory networks, in which epigenetic modifying enzymes play a crucial role. Histone lysine acetylation levels, modulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), are well-studied in the realm of transcriptional regulation. However, the advent of advanced proteomics has unveiled that non-histone proteins also undergo acetylation, with its underlying mechanisms now being clarified. Indeed, non-histone acetylation influences protein functionality through diverse pathways, such as modulating protein stability, adjusting enzymatic activity, steering subcellular localization, influencing interactions with other post-translational modifications, and managing protein-protein and protein-DNA interactions. This review delves into the recent insights into the functional mechanisms of non-histone acetylation in plants. We also provide a summary of the roles of HATs and HDACs in rice and Arabidopsis, and explore their potential involvement in the regulation of non-histone proteins.

Sexually dimorphic acetyl-CoA biosynthesis and utilization in response to drought and exogenous acetic acid

Female willows exhibit greater drought tolerance and benefit more from exogenous acetic acid (AA)-improved drought tolerance than males. However, the potential mechanisms driving these sex-specific responses remain unclear. To comprehensively investigate the sexually dimorphic responsive mechanisms of willows to drought and exogenous AA, here, we performed physiological, proteomic, Lys-acetylproteomic, and transgenic analyses in female and male Salix myrtillacea exposed to drought and AA-applicated drought treatments, focusing on protein abundance and lysine acetylation (LysAc) changes. Drought-tolerant females suffered less drought-induced photosynthetic and oxidative damage, did not activate AA and acetyl-CoA biosynthesis, TCA cycle, fatty acid metabolism, and jasmonic acid signaling as strongly as drought-sensitive males. Exogenous AA caused overaccumulation of endogenous AA and inhibition of acetyl-CoA biosynthesis and utilization in males. However, exogenous AA greatly enhanced acetyl-CoA biosynthesis and utilization and further enhanced drought performance of females, possibly determining that AA improved drought tolerance more in females than in males. Interestingly, overexpression of acetyl-CoA synthetase (ACS) could reprogram fatty acids, increase LysAc levels, and improve drought tolerance, highlighting the involvement of ACS-derived acetyl-CoA in drought responses. In addition, drought and exogenous AA induced sexually dimorphic LysAc associated with histones, transcription factors, and metabolic enzymes in willows. Especially, exogenous AA may greatly improve the photosynthetic capacity of S. myrtillacea males by decreasing LysAc levels and increasing the abundances of photosynthetic proteins. While hyperacetylation in glycolysis, TCA cycle, and fatty acid biosynthesis potentially possibly serve as negative feedback to acclimate acetyl-CoA biosynthesis and utilization in drought-stressed males and AA-applicated females. Thus, acetyl-CoA biosynthesis and utilization determine the sexually dimorphic responses of S. myrtillacea to drought and exogenous AA.

Chromatin sensing: integration of environmental signals to reprogram plant development through chromatin regulators

Chromatin regulation in eukaryotes plays pivotal roles in controlling the developmental regulatory gene network. This review explores the intricate interplay between chromatin regulators and environmental signals, elucidating their roles in shaping plant development. As sessile organisms, plants have evolved sophisticated mechanisms to perceive and respond to environmental cues, orchestrating developmental programs that ensure adaptability and survival. A central aspect of this dynamic response lies in the modulation of versatile gene regulatory networks, mediated in part by various chromatin regulators. Here, we summarized current understanding of the molecular mechanisms through which chromatin regulators integrate environmental signals, influencing key aspects of plant development.

Genome-wide identification and expression analysis of histone deacetylase and histone acetyltransferase genes in response to drought in poplars

BACKGROUND

Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are involved in plant growth and development as well as in response to environmental changes, by dynamically regulating gene acetylation levels. Although there have been numerous reports on the identification and function of HDAC and HAT in herbaceous plants, there are fewer report related genes in woody plants under drought stress.

RESULTS

In this study, we performed a genome-wide analysis of the HDAC and HAT families in Populus trichocarpa, including phylogenetic analysis, gene structure, conserved domains, and expression analysis. A total of 16 PtrHDACs and 12 PtrHATs were identified in P. trichocarpa genome. Analysis of cis-elements in the promoters of PtrHDACs and PtrHATs revealed that both gene families could respond to a variety of environmental signals, including hormones and drought. Furthermore, real time quantitative PCR indicated that PtrHDA906 and PtrHAG3 were significantly responsive to drought. PtrHDA906, PtrHAC1, PtrHAC3, PtrHAG2, PtrHAG6 and PtrHAF1 consistently responded to abscisic acid, methyl jasmonate and salicylic acid under drought conditions.

CONCLUSIONS

Our study demonstrates that PtrHDACs and PtrHATs may respond to drought through hormone signaling pathways, which helps to reveal the hub of acetylation modification in hormone regulation of abiotic stress.

The role of histone acetylation in transcriptional regulation and seed development

Histone acetylation is highly conserved across eukaryotes and has been linked to gene activation since its discovery nearly 60 years ago. Over the past decades, histone acetylation has been evidenced to play crucial roles in plant development and response to various environmental cues. Emerging data indicate that histone acetylation is one of the defining features of "open chromatin," while the role of histone acetylation in transcription remains controversial. In this review, we briefly describe the discovery of histone acetylation, the mechanism of histone acetylation regulating transcription in yeast and mammals, and summarize the research progress of plant histone acetylation. Furthermore, we also emphasize the effect of histone acetylation on seed development and its potential use in plant breeding. A comprehensive knowledge of histone acetylation might provide new and more flexible research perspectives to enhance crop yield and stress resistance.

GhWRKY4 binds to the histone deacetylase GhHDA8 promoter to regulate drought and salt tolerance in Gossypium hirsutum

Soil drought and salinization, caused by water deficiency, have become the greatest concerns limiting crop production. Up to now, the WRKY transcription factor and histone deacetylase have been shown to be involved in drought and salt responses. However, the molecular mechanism underlying their interaction remains unclear in cotton. Herein, we identified GhWRKY4, a member of WRKY gene family, which is induced by drought and salt stress and is located in the nucleus. The ectopic expression of GhWRKY4 in Arabidopsis enhanced drought and salt tolerance, and suppressing GhWRKY4 in cotton increased susceptibility to drought and salinity. Subsequently, DAP-seq analysis revealed that the W box element in the promoter of stress-induced genes could potentially be the binding target for GhWRKY4 protein. GhWRKY4 binds to the promoters of GhHDA8 and GhNHX7 via W box element, and the expression level of GhHDA8 was increased in GhWRKY4-silenced plants. In addition, GhHDA8-overexpressed Arabidopsis were found to be hypersensitive to drought and salt stress, while silencing of GhHDA8 enhanced drought and salt tolerance in cotton. The stress-related genes, such as GhDREB2A, GhRD22, GhP5CS, and GhNHX7, were induced in GhHDA8-silenced plants. Our findings indicate that the GhWRKY4-GhHDA8 module regulates drought and salt tolerance in cotton. Collectively, the results provide new insights into the coordination of transcription factors and histone deacetylases in regulating drought and salt stress responses in plants.

Genome-Wide Identification and Characterization of the Salvia miltiorrhiza Histone Deacetylase (HDAC) Family in Response to Multiple Abiotic Stresses

Salvia miltiorrhiza is a plant commonly used in traditional Chinese medicine. Its material bases for treating diseases are tanshinones and phenolic acids, including salvianolic acids. Histone deacetylase proteins (HDACs) are a class of specific functional enzymes that interact with acetylation groups on the N-terminal lysine of histone proteins further regulate gene transcription through structural changes at the chromatin level. HDACs involved in the growth and development of various plants, and induced by plant hormones to regulate the internal environment of plants to resist stress, at the same time affect the accumulation of some secondary metabolites. However, the role of SmHDACs on the accumulation of salvianolic acid in S. miltiorrhiza remains unclear. In this study, 16 SmHDACs genes were identified from the high-quality S. miltiorrhiza genome, their physicochemical properties were predicted. In phylogenetic trees co-constructed with HDACs proteins from other plants, SmHDACs was divided into three subfamilies, each with similar motif and conserved domain composition. The distribution of the three subfamilies is similar to that of dicotyledonous plants. Chromosome localization analysis showed that SmHDACs genes were randomly located. Cis-acting element analysis predicted that SmHDACs gene expression may be related to and induced by various phytohormones, such as MeJA and ABA. By combining the expression pattern and co-expression network induced by phytohormones, we speculate that SmHDACs may further influence the synthesis of salvianolic acid, and identified SmHDA5, a potential functional gene, then speculate its downstream target based on the co-expression network. In summary, we analyzed the SmHDACs gene family of S. miltiorrhiza and screened out the potential functional gene SmHDA5. From the perspective of epigenetics, we proposed the molecular mechanism of plant hormone promoting salvianolic acid synthesis, which filled the gap in the subdivision of histone deacetylase in S. miltiorrhiza research, provided a theoretical basis for the culture and transformation of S. miltiorrhiza germplasm resources.

Detection of the Arabidopsis Proteome and Its Post-translational Modifications and the Nature of the Unobserved (Dark) Proteome in PeptideAtlas

This study describes a new release of the Arabidopsis thaliana PeptideAtlas proteomics resource (build 2023-10) providing protein sequence coverage, matched mass spectrometry (MS) spectra, selected post-translational modifications (PTMs), and metadata. 70 million MS/MS spectra were matched to the Araport11 annotation, identifying ∼0.6 million unique peptides and 18,267 proteins at the highest confidence level and 3396 lower confidence proteins, together representing 78.6% of the predicted proteome. Additional identified proteins not predicted in Araport11 should be considered for the next Arabidopsis genome annotation. This release identified 5198 phosphorylated proteins, 668 ubiquitinated proteins, 3050 N-terminally acetylated proteins, and 864 lysine-acetylated proteins and mapped their PTM sites. MS support was lacking for 21.4% (5896 proteins) of the predicted Araport11 proteome: the "dark" proteome. This dark proteome is highly enriched for E3 ligases, transcription factors, and for certain (e.g., CLE, IDA, PSY) but not other (e.g., THIONIN, CAP) signaling peptides families. A machine learning model trained on RNA expression data and protein properties predicts the probability that proteins will be detected. The model aids in discovery of proteins with short half-life (e.g., SIG1,3 and ERF-VII TFs) and for developing strategies to identify the missing proteins. PeptideAtlas is linked to TAIR, tracks in JBrowse, and several other community proteomics resources.

Multifaceted functions of histone deacetylases in stress response

Histone deacetylases (HDACs) are important chromatin regulators essential for plant tolerance to adverse environments. In addition to histone deacetylation and epigenetic regulation, HDACs deacetylate non-histone proteins and thereby regulate multiple pathways. Like other post-translational modifications (PTMs), acetylation/deacetylation is a reversible switch regulating different cellular processes in plants. Here, by focusing on results obtained in arabidopsis (Arabidopsis thaliana) and rice plants, we analyze the different aspects of HDAC functions and the underlying regulatory mechanisms in modulating plant responses to stress. We hypothesize that, in addition to epigenetic regulation of gene expression, HDACs can also control plant tolerance to stress by regulating transcription, translation, and metabolic activities and possibly assembly-disassembly of stress granules (SGs) through lysine deacetylation of non-histone proteins.

CmoNAC1 in pumpkin rootstocks improves salt tolerance of grafted cucumbers by binding to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2 and CmoHKT1;1 to regulate H2O2, ABA signaling and K+/Na+ homeostasis

The NAC transcription factor is a type of plant-specific transcription factor that can regulate plant salt tolerance, but the underlying mechanism is unclear in grafted vegetables. H2O2 and ABA in pumpkin rootstocks can be transported to cucumber scion leaves, promoting stomatal closure to improve salt tolerance of grafted cucumbers. Despite these observations, the regulatory mechanism is unknown. Here, our research revealed that CmoNAC1 is a key transcription factor that regulates H2O2 and ABA signaling in pumpkin roots under salt stress. The function of CmoNAC1 was analyzed using root transformation and RNA-seq, and we found that pumpkin CmoNAC1 promoted the production of H2O2 and ABA via CmoRBOHD1 and CmoNCED6, respectively, and regulated K+/Na+ homeostasis via CmoAKT1;2, CmoHKT1;1, and CmoSOS1 to improve salt tolerance of grafted cucumbers. Root knockout of CmoNAC1 resulted in a significant decrease in H2O2 (52.9% and 32.1%) and ABA (21.8% and 42.7%) content and K+/Na+ ratio (81.5% and 56.3%) in leaf and roots of grafted cucumber, respectively, while overexpression showed the opposite effect. The root transformation experiment showed that CmoNCED6 could improve salt tolerance of grafted cucumbers by regulating ABA production and K+/Na+ homeostasis under salt stress. Finally, we found that CmoNAC1 bound to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2, and CmoHKT1;1 using yeast one-hybrid, luciferase, and electrophoretic mobility shift assays. In conclusion, pumpkin CmoNAC1 not only binds to the promoters of CmoRBOHD1 and CmoNCED6 to regulate the production of H2O2 and ABA signals in roots, but also binds to the promoters of CmoAKT1;2 and CmoHKT1;1 to increase the K+/Na+ ratio, thus improving salt tolerance of grafted cucumbers.

Mapping the Arabidopsis thaliana proteome in PeptideAtlas and the nature of the unobserved (dark) proteome; strategies towards a complete proteome

This study describes a new release of the Arabidopsis thaliana PeptideAtlas proteomics resource providing protein sequence coverage, matched mass spectrometry (MS) spectra, selected PTMs, and metadata. 70 million MS/MS spectra were matched to the Araport11 annotation, identifying ∼0.6 million unique peptides and 18267 proteins at the highest confidence level and 3396 lower confidence proteins, together representing 78.6% of the predicted proteome. Additional identified proteins not predicted in Araport11 should be considered for building the next Arabidopsis genome annotation. This release identified 5198 phosphorylated proteins, 668 ubiquitinated proteins, 3050 N-terminally acetylated proteins and 864 lysine-acetylated proteins and mapped their PTM sites. MS support was lacking for 21.4% (5896 proteins) of the predicted Araport11 proteome - the 'dark' proteome. This dark proteome is highly enriched for certain ( e.g. CLE, CEP, IDA, PSY) but not other ( e.g. THIONIN, CAP,) signaling peptides families, E3 ligases, TFs, and other proteins with unfavorable physicochemical properties. A machine learning model trained on RNA expression data and protein properties predicts the probability for proteins to be detected. The model aids in discovery of proteins with short-half life ( e.g. SIG1,3 and ERF-VII TFs) and completing the proteome. PeptideAtlas is linked to TAIR, JBrowse, PPDB, SUBA, UniProtKB and Plant PTM Viewer.