In silico analysis of protein Lys-N(𝜀)-acetylation in plants

Spotlight on Plant Bromodomain Proteins

Bromodomain-containing proteins (BRD-proteins) are the "readers" of histone lysine acetylation, translating chromatin state into gene expression. They act alone or as components of larger complexes and exhibit diverse functions to regulate gene expression; they participate in chromatin remodeling complexes, mediate histone modifications, serve as scaffolds to recruit transcriptional regulators or act themselves as transcriptional co-activators or repressors. Human BRD-proteins have been extensively studied and have gained interest as potential drug targets for various diseases, whereas in plants, this group of proteins is still not well investigated. In this review, we aimed to concentrate scientific knowledge on these chromatin "readers" with a focus on Arabidopsis. We organized plant BRD-proteins into groups based on their functions and domain architecture and summarized the published work regarding their interactions, activity and diverse functions. Overall, it seems that plant BRD-proteins are indispensable components and fine-tuners of the complex network plants have built to regulate development, flowering, hormone signaling and response to various biotic or abiotic stresses. This work will facilitate the understanding of their roles in plants and highlight BRD-proteins with yet undiscovered functions.

Genome-wide analysis of bromodomain gene family in Arabidopsis and rice

The bromodomain-containing proteins (BRD-proteins) belongs to family of 'epigenetic mark readers', integral to epigenetic regulation. The BRD-members contain a conserved 'bromodomain' (BRD/BRD-fold: interacts with acetylated-lysine in histones), and several additional domains, making them structurally/functionally diverse. Like animals, plants also contain multiple Brd-homologs, however the extent of their diversity and impact of molecular events (genomic duplications, alternative splicing, AS) therein, is relatively less explored. The present genome-wide analysis of Brd-gene families of Arabidopsis thaliana and Oryza sativa showed extensive diversity in structure of genes/proteins, regulatory elements, expression pattern, domains/motifs, and the bromodomain (w.r.t. length, sequence, location) among the Brd-members. Orthology analysis identified thirteen ortholog groups (OGs), three paralog groups (PGs) and four singleton members (STs). While more than 40% Brd-genes were affected by genomic duplication events in both plants, AS-events affected 60% A. thaliana and 41% O. sativa genes. These molecular events affected various regions (promoters, untranslated regions, exons) of different Brd-members with potential impact on expression and/or structure-function characteristics. RNA-Seq data analysis indicated differences in tissue-specificity and stress response of Brd-members. Analysis by RT-qPCR revealed differential abundance and salt stress response of duplicate A. thaliana and O. sativa Brd-genes. Further analysis of AtBrd gene, AtBrdPG1b showed salinity-induced modulation of splicing pattern. Bromodomain (BRD)-region based phylogenetic analysis placed the A. thaliana and O. sativa homologs into clusters/sub-clusters, mostly consistent with ortholog/paralog groups. The bromodomain-region displayed several conserved signatures in key BRD-fold elements (α-helices, loops), along with variations (1-20 sites) and indels among the BRD-duplicates. Homology modeling and superposition identified structural variations in BRD-folds of divergent and duplicate BRD-members, which might affect their interaction with the chromatin histones, and associated functions. The study also showed contribution of various duplication events in Brd-gene family expansion among diverse plants, including several monocot and dicot plant species.

Global analysis of lysine acetylation in soybean leaves

Protein lysine acetylation (Kac) is an important post-translational modification in both animal and plant cells. Global Kac identification has been performed at the proteomic level in various species. However, the study of Kac in oil and resource plant species is relatively limited. Soybean is a globally important oil crop and resouce plant. In the present study, lysine acetylome analysis was performed in soybean leaves with proteomics techniques. Various bioinformatics analyses were performed to illustrate the structure and function of these Kac sites and proteins. Totally, 3148 acetylation sites in 1538 proteins were detected. Motif analysis of these Kac modified peptides extracted 17 conserved motifs. These Kac modified protein showed a wide subcellular location and functional distribution. Chloroplast is the primary subcellular location and cellular component where Kac proteins were localized. Function and pathways analyses indicated a plenty of biological processes and metabolism pathways potentially be influenced by Kac modification. Ribosome activity and protein biosynthesis, carbohydrate and energy metabolism, photosynthesis and fatty acid metabolism may be regulated by Kac modification in soybean leaves. Our study suggests Kac plays an important role in soybean physiology and biology, which is an available resource and reference of Kac function and structure characterization in oil crop and resource plant, as well as in plant kingdom.

Bromodomain-containing subunits BRD1, BRD2, and BRD13 are required for proper functioning of SWI/SNF complexes in Arabidopsis

SWI/SNF chromatin remodelers are evolutionarily conserved multiprotein complexes that use the energy of ATP hydrolysis to change chromatin structure. A characteristic feature of SWI/SNF remodelers is the occurrence in both the catalytic ATPase subunit and some auxiliary subunits, of bromodomains, the protein motifs capable of binding acetylated histones. Here, we report that the Arabidopsis bromodomain-containing proteins BRD1, BRD2, and BRD13 are likely true SWI/SNF subunits that interact with the core SWI/SNF components SWI3C and SWP73B. Loss of function of each single BRD protein caused early flowering but had a negligible effect on other developmental pathways. By contrast, a brd triple mutation (brdx3) led to more pronounced developmental abnormalities, indicating functional redundancy among the BRD proteins. The brdx3 phenotypes, including hypersensitivity to abscisic acid and the gibberellin biosynthesis inhibitor paclobutrazol, resembled those of swi/snf mutants. Furthermore, the BRM protein level and occupancy at the direct target loci SCL3, ABI5, and SVP were reduced in the brdx3 mutant background. Finally, a brdx3 brm-3 quadruple mutant, in which SWI/SNF complexes were devoid of all constituent bromodomains, phenocopied a loss-of-function mutation in BRM. Taken together, our results demonstrate the relevance of BRDs as SWI/SNF subunits and suggest their cooperation with the bromodomain of BRM ATPase.

Bromodomain-containing proteins BRD1, BRD2, and BRD13 are core subunits of SWI/SNF complexes and vital for their genomic targeting in Arabidopsis

Switch defective/sucrose non-fermentable (SWI/SNF) chromatin remodeling complexes are multi-subunit machines that play vital roles in the regulation of chromatin structure and gene expression. However, the mechanisms by which SWI/SNF complexes recognize their target loci in plants are not fully understood. Here, we show that the Arabidopsis thaliana bromodomain-containing proteins BRD1, BRD2, and BRD13 are core subunits of SWI/SNF complexes and critical for SWI/SNF genomic targeting. These three BRDs interact directly with multiple SWI/SNF subunits, including the BRAHMA (BRM) catalytic subunit. Phenotypic and transcriptomic analyses of the brd1 brd2 brd13 triple mutant revealed that these BRDs act largely redundantly to control gene expression and developmental processes that are also regulated by BRM. Genome-wide occupancy profiling demonstrated that these three BRDs extensively colocalize with BRM on chromatin. Simultaneous loss of function of three BRD genes results in reduced BRM protein levels and decreased occupancy of BRM on chromatin across the genome. Furthermore, we demonstrated that the bromodomains of BRDs are essential for genomic targeting of the BRD subunits of SWI/SNF complexes to their target sites. Collectively, these results demonstrate that BRD1, BRD2, and BRD13 are core subunits of SWI/SNF complexes and reveal their biological roles in facilitating genomic targeting of BRM-containing SWI/SNF complexes in plants.

Poplar acetylome profiling reveals lysine acetylation dynamics in seasonal bud dormancy release

For perennials in boreal and temperate ecosystems, bud dormancy is crucial for survival in harsh winter. Dormancy is released by prolonged exposure to low temperatures and is followed by reactive growth in the spring. Lysine acetylation (Kac) is one of the major post-translational modifications (PTMs) that are involved in plant response to environmental signals. However, little information is available on the effects of Kac modification on bud dormancy release. Here, we report the dynamics of lysine acetylome in hybrid poplar (Populus tremula × Populus alba) dormant buds. A total of 7,594 acetyl-sites from 3,281 acetyl-proteins were identified, representing a large dataset of lysine acetylome in plants. Of them, 229 proteins were differentially acetylated during bud dormancy release and were mainly involved in the primary metabolic pathways. Site-directed mutagenesis enzymatic assays showed that Kac strongly modified the activities of two key enzymes of primary metabolism, pyruvate dehydrogenase (PDH) and isocitrate dehydrogenase (IDH). We thus propose that Kac of enzymes could be an important strategy for reconfiguration of metabolic processes during bud dormancy release. In all, our results reveal the importance of Kac in bud dormancy release and provide a new perspective to understand the molecular mechanisms of seasonal growth of trees.

Diurnal dynamics of the Arabidopsis rosette proteome and phosphoproteome

Plant growth depends on the diurnal regulation of cellular processes, but it is not well understood if and how transcriptional regulation controls diurnal fluctuations at the protein level. Here, we report a high-resolution Arabidopsis thaliana (Arabidopsis) leaf rosette proteome acquired over a 12 hr light:12 hr dark diurnal cycle and the phosphoproteome immediately before and after the light-to-dark and dark-to-light transitions. We quantified nearly 5,000 proteins and 800 phosphoproteins, of which 288 fluctuated in their abundance and 226 fluctuated in their phosphorylation status. Of the phosphoproteins, 60% were quantified for changes in protein abundance. This revealed six proteins involved in nitrogen and hormone metabolism that had concurrent changes in both protein abundance and phosphorylation status. The diurnal proteome and phosphoproteome changes involve proteins in key cellular processes, including protein translation, light perception, photosynthesis, metabolism and transport. The phosphoproteome at the light-dark transitions revealed the dynamics at phosphorylation sites in either anticipation of or response to a change in light regime. Phosphorylation site motif analyses implicate casein kinase II and calcium/calmodulin-dependent kinases among the primary light-dark transition kinases. The comparative analysis of the diurnal proteome and diurnal and circadian transcriptome established how mRNA and protein accumulation intersect in leaves during the diurnal cycle of the plant.

Proteome and lysine acetylome analysis reveals insights into the molecular mechanism of seed germination in wheat

Seed germination is the first stage in wheat growth and development, directly affecting grain yield and quality. As an important post-translation modification, lysine acetylation participates in diverse biological functions. However, little is known regarding the quantitative acetylproteome characterization during wheat seed germination. In this study, we generated the first comparative proteomes and lysine acetylomes during wheat seed germination. In total, 5,639 proteins and 1,301 acetylated sites on 722 proteins were identified at 0, 12 and 24 h after imbibitions. Several particularly preferred amino acids were found near acetylation sites, including K^acS, K^acT, K^acK, K^acR, K^acH, K^acF, K^acN, K^ac*E, FK^ac and K^ac*D, in the embryos during seed germination. Among them, K^acH, K^acF, FK^ac and K^acK were conserved in wheat. Biosynthetic process, transcriptional regulation, ribosome and proteasome pathway related proteins were significantly enriched in both differentially expressed proteins and differentially acetylated proteins through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis. We also revealed that histone acetylation was differentially involved in epigenetic regulation during seed germination. Meanwhile, abscisic acid and stress related proteins were found with acetylation changes. In addition, we focused on 8 enzymes involved in carbohydrate metabolism, and found they were differentially acetylated during seed germination. Finally, a putative metabolic pathway was proposed to dissect the roles of protein acetylation during wheat seed germination. These results not only demonstrate that lysine acetylation may play key roles in seed germination of wheat but also reveal insights into the molecular mechanism of seed germination in this crop.

Blocking the Bromodomains Function Contributes to Disturbances in Alga Chara vulgaris Spermatids Differentiation

Bromodomain containing (BRD) proteins play an essential role in many cellular processes. The aim of this study was to estimate activity of bromodomains during alga Chara vulgaris spermatids differentiation. The effect of a bromodomain inhibitor, JQ1 (100 μM), on the distribution of individual stages of spermatids and their ultrastructure was studied. The material was Feulgen stained and analysed in an electron microscope. JQ1 caused shortening of the early stages of spermiogenesis and a reverse reaction at the later stages. Additionally, in the same antheridium, spermatids at distant developmental stages were present. On the ultrastructural level, chromatin fibril system disorders and significantly distended endoplasmic reticulum (ER) cisternae already at the early stages were observed. Many autolytic vacuoles were also visible. The ultrastructural disturbances intensified after prolonged treatment with JQ1. The obtained data show that JQ1 treatment led to changes in the spermatid number and disturbances in chromatin condensation and to cytoplasm reduction. The current studies show some similarities between C. vulgaris and mammals spermiogenesis. Taken together, these results suggest that JQ1 interferes with the spermatid differentiation on many interdependent levels and seems to induce ER stress, which leads to spermatid degeneration. Studies on the role of bromodomains in algae spermiogenesis have not been conducted so far.

Diurnal changes in concerted plant protein phosphorylation and acetylation in Arabidopsis organs and seedlings

Protein phosphorylation and acetylation are the two most abundant post-translational modifications (PTMs) that regulate protein functions in eukaryotes. In plants, these PTMs have been investigated individually; however, their co-occurrence and dynamics on proteins is currently unknown. Using Arabidopsis thaliana, we quantified changes in protein phosphorylation, acetylation and protein abundance in leaf rosettes, roots, flowers, siliques and seedlings at the end of day (ED) and at the end of night (EN). This identified 2549 phosphorylated and 909 acetylated proteins, of which 1724 phosphorylated and 536 acetylated proteins were also quantified for changes in PTM abundance between ED and EN. Using a sequential dual-PTM workflow, we identified significant PTM changes and intersections in these organs and plant developmental stages. In particular, cellular process-, pathway- and protein-level analyses reveal that the phosphoproteome and acetylome predominantly intersect at the pathway- and cellular process-level at ED versus EN. We found 134 proteins involved in core plant cell processes, such as light harvesting and photosynthesis, translation, metabolism and cellular transport, that were both phosphorylated and acetylated. Our results establish connections between PTM motifs, PTM catalyzing enzymes and putative substrate networks. We also identified PTM motifs for further characterization of the regulatory mechanisms that control cellular processes during the diurnal cycle in different Arabidopsis organs and seedlings. The sequential dual-PTM analysis expands our understanding of diurnal plant cell regulation by PTMs and provides a useful resource for future analyses, while emphasizing the importance of analyzing multiple PTMs simultaneously to elucidate when, where and how they are involved in plant cell regulation.

New insights into the heat responses of grape leaves via combined phosphoproteomic and acetylproteomic analyses

Heat stress is a serious and widespread threat to the quality and yield of many crop species, including grape (Vitis vinifera L.), which is cultivated worldwide. Here, we conducted phosphoproteomic and acetylproteomic analyses of leaves of grape plants cultivated under four distinct temperature regimes. The phosphorylation or acetylation of a total of 1011 phosphoproteins with 1828 phosphosites and 96 acetyl proteins with 148 acetyl sites changed when plants were grown at 35 °C, 40 °C, and 45 °C in comparison with the proteome profiles of plants grown at 25 °C. The greatest number of changes was observed at the relatively high temperatures. Functional classification and enrichment analysis indicated that phosphorylation, rather than acetylation, of serine/arginine-rich splicing factors was involved in the response to high temperatures. This finding is congruent with previous observations by which alternative splicing events occurred more frequently in grapevine under high temperature. Changes in acetylation patterns were more common than changes in phosphorylation patterns in photosynthesis-related proteins at high temperatures, while heat-shock proteins were associated more with modifications involving phosphorylation than with those involving acetylation. Nineteen proteins were identified with changes associated with both phosphorylation and acetylation, which is consistent with crosstalk between these posttranslational modification types.

Comprehensive proteome analyses of lysine acetylation in tea leaves by sensing nitrogen nutrition

Background

N^ε-Acetylation of lysine residues, a frequently occurring post-translational modification, plays important functions in regulating physiology and metabolism. However, the information of global overview of protein acetylome under nitrogen-starvation/resupply in tea (Camellia sinensis) leaves was limited. And the full function of lysine acetylated proteins of tea plants in nitrogen absorption and assimilation remains unclear.

Results

Here, we performed the global review of lysine acetylome in tea leaves under nitrogen (N)-starvation/resupply, using peptide prefractionation, immunoaffinity enrichment, and coupling with high sensitive LC-MS/MS combined with affinity purification analysis. Altogether, 2229 lysine acetylation sites on 1286 proteins were identified, of which 16 conserved motifs in E^*K^acK, K^ac*K, K^ac*R, K^ac*HK, K^ac*N, K^ac*S, K^ac*T, K^ac*D, were extracted from 2180 acetylated peptides. Approximately, 36.76% of the acetylated lysines were located in the regions of ordered secondary structures. The most of the identified lysine acetylation proteins were located in the chloroplast (39%) and cytoplasm (29%). The largest group of acetylated proteins consisted of many enzymes, such as ATP synthase, ribosomal proteins and malate dehydrogenase [NADP], which were related to metabolism (38%) in the biological process. These acetylated proteins were mainly enriched in three primary protein complexes of photosynthesis: photosystem I, photosystem II and the cytochrome b6/f complex. And some acetylated proteins related to glycolysis and secondary metabolite biosynthesis were increased/decreased under N-resupply. Moreover, the PPI (protein-protein interaction) analysis revealed that the diverse interactions of identified acetylated proteins mainly involved in photosynthesis and ribosome.

Conclusion

The results suggested that lysine acetylated proteins might play regulating roles in metabolic process in tea leaves. The critical regulatory roles mainly involved in diverse aspects of metabolic processes, especially in photosynthesis, glycolysis and secondary metabolism. A lot of proteins related to the photosynthesis and glycolysis were found to be acetylated, including LHCA1, LHCA3, LHCB6, psaE, psaD, psaN, GAPDH, PEPC, ENL and petC. And some proteins related to flavonoids were also found to be acetylated, including PAL, DFR, naringenin 3-dioxygenase and CHI. The provided data may serve as important resources for exploring the physiological, biochemical, and genetic role of lysine acetylation in tea plants. Data are available via ProteomeXchange with identifier PXD008931.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5250-4) contains supplementary material, which is available to authorized users.

First comprehensive analysis of lysine acetylation in Alvinocaris longirostris from the deep-sea hydrothermal vents

Background

Deep-sea hydrothermal vents are unique chemoautotrophic ecosystems with harsh conditions. Alvinocaris longirostris is one of the dominant crustacean species inhabiting in these extreme environments. It is significant to clarify mechanisms in their adaptation to the vents. Lysine acetylation has been known to play critical roles in the regulation of many cellular processes. However, its function in A. longirostris and even marine invertebrates remains elusive. Our study is the first, to our knowledge, to comprehensively investigate lysine acetylome in A. longirostris.

Results

In total, 501 unique acetylation sites from 206 proteins were identified by combination of affinity enrichment and high-sensitive-massspectrometer. It was revealed that Arg, His and Lys occurred most frequently at the + 1 position downstream of the acetylation sites, which were all alkaline amino acids and positively charged. Functional analysis revealed that the protein acetylation was involved in diverse cellular processes, such as biosynthesis of amino acids, citrate cycle, fatty acid degradation and oxidative phosphorylation. Acetylated proteins were found enriched in mitochondrion and peroxisome, and many stress response related proteins were also discovered to be acetylated, like arginine kinases, heat shock protein 70, and hemocyanins. In the two hemocyanins, nine acetylation sites were identified, among which one acetylation site was unique in A. longirostris when compared with other shallow water shrimps. Further studies are warranted to verify its function.

Conclusion

The lysine acetylome of A. longirostris is investigated for the first time and brings new insights into the regulation function of the lysine acetylation. The results supply abundant resources for exploring the functions of acetylation in A. longirostris and other shrimps.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4745-3) contains supplementary material, which is available to authorized users.

A phosphoproteomic landscape of rice (Oryza sativa) tissues

Protein phosphorylation is an important posttranslational modification that regulates various plant developmental processes. Here, we report a comprehensive, quantitative phosphoproteomic profile of six rice tissues, including callus, leaf, root, shoot meristem, young panicle and mature panicle from Nipponbare by employing a mass spectrometry (MS)-based, label-free approach. A total of 7171 unique phosphorylation sites in 4792 phosphopeptides from 2657 phosphoproteins were identified, of which 4613 peptides were differentially phosphorylated (DP) among the tissues. Motif-X analysis revealed eight significantly enriched motifs, such as [sP], [Rxxs] and [tP] from the rice phosphosites. Hierarchical clustering analysis divided the DP peptides into 63 subgroups, which showed divergent spatial-phosphorylation patterns among tissues. These clustered proteins are functionally related to nutrition uptake in roots, photosynthesis in leaves and tissue differentiation in panicles. Phosphorylations were specific in the tissues where the target proteins execute their functions, suggesting that phosphorylation might be a key mechanism to regulate the protein activity in different tissues. This study greatly expands the rice phosphoproteomic dataset, and also offers insight into the regulatory roles of phosphorylation in tissue development and functions.

Modelling the three-dimensional structure of the right-terminal domain of pospiviroids

Viroids, the smallest know plant pathogens, consist solely of a circular, single-stranded, non-coding RNA. Thus for all of their biological functions, like replication, processing, and transport, they have to present sequence or structural features to exploit host proteins. Viroid binding protein 1 (Virp1) is indispensable for replication of pospiviroids, the largest genus of viroids, in a host plant as well as in protoplasts. Virp1 is known to bind at two sites in the terminal right (TR) domain of pospiviroids; each site consists of a purine- (R-) and a pyrimidine- (Y-)rich motif that are partially base-paired to each other. Here we model the important structural features of the domain and show that it contains an internal loop of two Y · Y cis Watson-Crick/Watson-Crick (cWW) pairs, an asymmetric internal loop including a cWW and a trans Watson/Hoogsteen pair, and a thermodynamically quite stable hairpin loop with several stacking interactions. These features are discussed in connection to the known biological functions of the TR domain.

First Comprehensive Proteome Analyses of Lysine Acetylation and Succinylation in Seedling Leaves of Brachypodium distachyon L

Protein acetylation and succinylation are the most crucial protein post-translational modifications (PTMs) involved in the regulation of plant growth and development. In this study, we present the first lysine-acetylation and lysine-succinylation proteome analysis of seedling leaves in Brachypodium distachyon L (Bd). Using high accuracy nano LC-MS/MS combined with affinity purification, we identified a total of 636 lysine-acetylated sites in 353 proteins and 605 lysine-succinylated sites in 262 proteins. These proteins participated in many biology processes, with various molecular functions. In particular, 119 proteins and 115 sites were found to be both acetylated and succinylated, simultaneously. Among the 353 acetylated proteins, 148 had acetylation orthologs in Oryza sativa L., Arabidopsis thaliana, Synechocystis sp. PCC 6803, and Glycine max L. Among the 262 succinylated proteins, 170 of them were found to have homologous proteins in Oryza sativa L., Escherichia coli, Sacchayromyces cerevisiae, or Homo sapiens. Motif-X analysis of the acetylated and succinylated sites identified two new acetylated motifs (K---K and K-I-K) and twelve significantly enriched succinylated motifs for the first time, which could serve as possible binding loci for future studies in plants. Our comprehensive dataset provides a promising starting point for further functional analysis of acetylation and succinylation in Bd and other plant species.

Comprehensive profiling of lysine acetylproteome analysis reveals diverse functions of lysine acetylation in common wheat

Lysine acetylation of proteins, a dynamic and reversible post-translational modification, plays a critical regulatory role in both eukaryotes and prokaryotes. Several researches have been carried out on acetylproteome in plants. However, until now, there have been no data on common wheat, the major cereal crop in the world. In this study, we performed a global acetylproteome analysis of common wheat variety (Triticum aestivum L.), Chinese Spring. In total, 416 lysine modification sites were identified on 277 proteins, which are involved in a wide variety of biological processes. Consistent with previous studies, a large proportion of the acetylated proteins are involved in metabolic process. Interestingly, according to the functional enrichment analysis, 26 acetylated proteins are involved in photosynthesis and Calvin cycle, suggesting an important role of lysine acetylation in these processes. Moreover, protein interaction network analysis reveals that diverse interactions are modulated by protein acetylation. These data represent the first report of acetylome in common wheat and serve as an important resource for exploring the physiological role of lysine acetylation in this organism and likely in all plants.

Posttranslational Modifications of Chloroplast Proteins: An Emerging Field

Posttranslational modifications of proteins are key effectors of enzyme activity, protein interactions, targeting, and turnover rate, but despite their importance, they are still poorly understood in plants. Although numerous reports have revealed the regulatory role of protein phosphorylation in photosynthesis, various other protein modifications have been identified in chloroplasts only recently. It is known that posttranslational N(α)-acetylation occurs in both nuclear- and plastid-encoded chloroplast proteins, but the physiological significance of this acetylation is not yet understood. Lysine acetylation affects the localization and activity of key metabolic enzymes, and it may work antagonistically or cooperatively with lysine methylation, which also occurs in chloroplasts. In addition, tyrosine nitration may help regulate the repair cycle of photosystem II, while N-glycosylation determines enzyme activity of chloroplastic carbonic anhydrase. This review summarizes the progress in the research field of posttranslational modifications of chloroplast proteins and points out the importance of these modifications in the regulation of chloroplast metabolism.

Global analysis of lysine acetylation in strawberry leaves

Protein lysine acetylation is a reversible and dynamic post-translational modification. It plays an important role in regulating diverse cellular processes including chromatin dynamic, metabolic pathways, and transcription in both prokaryotes and eukaryotes. Although studies of lysine acetylome in plants have been reported, the throughput was not high enough, hindering the deep understanding of lysine acetylation in plant physiology and pathology. In this study, taking advantages of anti-acetyllysine-based enrichment and high-sensitive-mass spectrometer, we applied an integrated proteomic approach to comprehensively investigate lysine acetylome in strawberry. In total, we identified 1392 acetylation sites in 684 proteins, representing the largest dataset of acetylome in plants to date. To reveal the functional impacts of lysine acetylation in strawberry, intensive bioinformatic analysis was performed. The results significantly expanded our current understanding of plant acetylome and demonstrated that lysine acetylation is involved in multiple cellular metabolism and cellular processes. More interestingly, nearly 50% of all acetylated proteins identified in this work were localized in chloroplast and the vital role of lysine acetylation in photosynthesis was also revealed. Taken together, this study not only established the most extensive lysine acetylome in plants to date, but also systematically suggests the significant and unique roles of lysine acetylation in plants.