Crop proteomics: Aim at sustainable agriculture of tomorrow

In Situ Proteomic Analysis of Herbicide-Resistant Soybean and Hybrid Seeds via Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging

Transgenic soybean is the commercial crop with the largest cultivation area worldwide. During transgenic soybean cultivation, exogenous genes may be transferred to wild relatives through gene flow, posing unpredictable ecological risks. Accordingly, an environmental risk assessment should focus on fitness changes and underlying mechanisms in hybrids between transgenic and wild soybeans (Glycine soja). Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) was used for in situ detection and imaging of protein changes in the seeds of transgenic herbicide-resistant soybean harboring epsps and pat genes, non-transgenic soybean, wild soybean, and their F₂ hybrid. Protein data clearly distinguished wild soybeans, while the F₂ seeds had protein characteristics of both parents and were distinguished from wild soybean seeds. Using UPLC-Q-TOF-MS, 22 differentially expressed proteins (DEPs) were identified, including 13 specific to wild soybean. Sucrose synthase and stress response-related DEPs were differentially expressed in parental and offspring. Differences in these may underpin the greater adaptability of the latter. MSI revealed DEP distribution in transgenic, wild, and F₂ seeds. Identifying DEPs related to fitness may elucidate mechanisms underlying fitness differences among the studied varieties. Our study shows that MALDI-MSI has the potential to become a visual method for transgenic soybean analysis.

Plant Metabolomics: An Overview of the Role of Primary and Secondary Metabolites against Different Environmental Stress Factors

Several environmental stresses, including biotic and abiotic factors, adversely affect the growth and development of crops, thereby lowering their yield. However, abiotic factors, e.g., drought, salinity, cold, heat, ultraviolet radiations (UVr), reactive oxygen species (ROS), trace metals (TM), and soil pH, are extremely destructive and decrease crop yield worldwide. It is expected that more than 50% of crop production losses are due to abiotic stresses. Moreover, these factors are responsible for physiological and biochemical changes in plants. The response of different plant species to such stresses is a complex phenomenon with individual features for several species. In addition, it has been shown that abiotic factors stimulate multi-gene responses by making modifications in the accumulation of the primary and secondary metabolites. Metabolomics is a promising way to interpret biotic and abiotic stress tolerance in plants. The study of metabolic profiling revealed different types of metabolites, e.g., amino acids, carbohydrates, phenols, polyamines, terpenes, etc, which are accumulated in plants. Among all, primary metabolites, such as amino acids, carbohydrates, lipids polyamines, and glycine betaine, are considered the major contributing factors that work as osmolytes and osmoprotectants for plants from various environmental stress factors. In contrast, plant-derived secondary metabolites, e.g., phenolics, terpenoids, and nitrogen-containing compounds (alkaloids), have no direct role in the growth and development of plants. Nevertheless, such metabolites could play a significant role as a defense by protecting plants from biotic factors such as herbivores, insects, and pathogens. In addition, they can enhance the resistance against abiotic factors. Therefore, metabolomics practices are becoming essential and influential in plants by identifying different phytochemicals that are part of the acclimation responses to various stimuli. Hence, an accurate metabolome analysis is important to understand the basics of stress physiology and biochemistry. This review provides insight into the current information related to the impact of biotic and abiotic factors on variations of various sets of metabolite levels and explores how primary and secondary metabolites help plants in response to these stresses.

Integrated physiological and comparative proteomics analysis of contrasting genotypes of pearl millet reveals underlying salt-responsive mechanisms

Salinity stress poses a significant risk to plant development and agricultural yield. Therefore, elucidation of stress-response mechanisms has become essential to identify salt-tolerance genes in plants. In the present study, two genotypes of pearl millet (Pennisetum glaucum L.) with contrasting tolerance for salinity exhibited differential morpho-physiological and proteomic responses under 150 mM NaCl. The genotype IC 325825 was shown to withstand the stress better than IP 17224. The salt-tolerance potential of IC 325825 was associated with its ability to maintain intracellular osmotic, ionic, and redox homeostasis and membrane integrity under stress. The IC 325825 genotype exhibited a higher abundance of C4 photosynthesis enzymes, efficient enzymatic and non-enzymatic antioxidant system, and lower Na⁺ /K⁺ ratio compared with IP 17224. Comparative proteomics analysis revealed greater metabolic perturbation in IP 17224 under salinity, in contrast to IC 325825 that harbored pro-active stress-responsive machinery, allowing its survival and better adaptability under salt stress. The differentially abundant proteins were in silico characterized for their functions, subcellular-localization, associated pathways, and protein-protein interaction. These proteins were mainly involved in photosynthesis/response to light stimulus, carbohydrate and energy metabolism, and stress responses. Proteomics data were validated through expression profiling of the selected genes, revealing a poor correlation between protein abundance and their relative transcript levels. This study has provided novel insights into salt adaptive mechanisms in P. glaucum, demonstrating the power of proteomics-based approaches. The critical proteins identified in the present study could be further explored as potential objects for engineering stress tolerance in salt-sensitive major crops.

Application of Mass Spectrometry-Based Proteomics to Barley Research

Barley (Hordeum vulgare) is the fourth most cultivated crop in the world in terms of production volume, and it is also the most important raw material of the malting and brewing industries. Barley belongs to the grass (Poaceae) family and plays an important role in food security and food safety for both humans and livestock. With the global population set to reach 9.7 billion by 2050, but with less available and/or suitable land for agriculture, the use of biotechnology tools in breeding programs are of considerable importance in the quest to meet the growing food gap. Proteomics as a member of the "omics" technologies has become popular for the investigation of proteins in cereal crops and particularly barley and its related products such as malt and beer. This technology has been applied to study how proteins in barley respond to adverse environmental conditions including abiotic and/or biotic stresses, how they are impacted during food processing including malting and brewing, and the presence of proteins implicated in celiac disease. Moreover, proteomics can be used in the future to inform breeding programs that aim to enhance the nutritional value and broaden the application of this crop in new food and beverage products. Mass spectrometry analysis is a valuable tool that, along with genomics and transcriptomics, can inform plant breeding strategies that aim to produce superior barley varieties. In this review, recent studies employing both qualitative and quantitative mass spectrometry approaches are explored with a focus on their application in cultivation, manufacturing, processing, quality, and the safety of barley and its related products.

Histological and proteome analyses of Microbacterium foliorum-mediated decrease in arsenic toxicity in Melastoma malabathricum

Arsenic (As) is an increasing threat across the globe, widely known as a non-threshold carcinogen, and it is reaching harmful values in several areas of the world. In this study, the effect of plant growth promoting bacteria (Microbacterium foliorum) on inorganic arsenic (Arsenate) phytoremediation by Melastoma malabathricum plants was investigated through histological analysis and proteome profiling of the M. malabathricum plants. Two-dimensional gel electrophoresis and transmission electron microscopy were used to conduct the proteome and histological analysis. When arsenic-treated cells were compared to untreated cells, substantial changes were found (1) severely altered the morphology of the cells, intensely disturbed; (2) the cell wall was thicker; (3) drastically changed the cytoplasm, the cells were polygonal in shape, different in size (scattered), and relatively dense. Compared to the control group, the ultra-structure of the root cells of the control group revealed intact cytoplasm, vacuole, and cell wall under exposure to As + bacteria that had a minor effect on the cell form. To further understand As + bacteria interaction, proteome profiling of the root cell was analyzed. The As-induced oxidative stress enrichment was confirmed by the up-regulation of tubulin, nucleoside diphosphate kinase, and major allergen during As + bacteria exposure It was observed that the profusion of proteins involved in defence, protein biogenesis, signaling, photosynthesis, nucleoside and energy metabolism was greater in As + bacteria as compared to the rooting out of As only. Overall, it can be obviously seen that the current study demonstrates the effectiveness of phytoremediation by M. foliorum on proteins involved and responsive pathways in dealing with As toxicity in M. malabathricum plant.

Root endophytic fungus Serendipita indica modulates barley leaf blade proteome by increasing the abundance of photosynthetic proteins in response to salinity

AIMS

The present study aimed at analysing the proteome pattern of the leaf blade of barley (Hordeum vulgare L.) in Serendipita indica-colonised plants to decipher the molecular mechanism of S. indica-mediated salt stress. This work is aligned with our previous research on barley leaf sheath to study proteomic pattern variability in leaf blade and sheath of barley plant in response to salinity and S. indica inoculation.

METHODS AND RESULTS

The experiment was conducted using a completely randomised factorial design with four replications and two treatments: salinity (0 and 300 mmol l^-1 NaCl) and fungus (noninoculated and S. indica-inoculated). The leaf blades of the salt-treated S. indica-colonised and noninoculated plants were harvested after 2 weeks of salt treatment for the physiological and proteomic analyses. After exposure to 300 mmol l^-1 NaCl, shoot dry matter production in noninoculated control plants decreased 84% which was about twofold higher than inoculated plants with S. indica. However, the accumulation of sodium in the shoot of S. indica-inoculated plants was significantly lower than the control plants. Analysis of the proteome profile revealed a high number of significantly up-regulated proteins involved in photosynthesis (26 out of 42 identified proteins).

CONCLUSIONS

The results demonstrated how the enhanced plant growth and salt stress resistance induced by S. indica was positively associated with the up-regulation of several proteins involved in photosynthesis and carbohydrate metabolism. In fact, S. indica improved photosynthesis in order to reach the best possible performance of the host plant under salt stress.

SIGNIFICANCE AND IMPACT OF THE STUDY

Current research provides new insight into the mechanism applied by S. indica in reducing the negative impacts of salt stress in barley at physiological and molecular levels.

PANOMICS meets germplasm

Genotyping-by-sequencing has enabled approaches for genomic selection to improve yield, stress resistance and nutritional value. More and more resource studies are emerging providing 1000 and more genotypes and millions of SNPs for one species covering a hitherto inaccessible intraspecific genetic variation. The larger the databases are growing, the better statistical approaches for genomic selection will be available. However, there are clear limitations on the statistical but also on the biological part. Intraspecific genetic variation is able to explain a high proportion of the phenotypes, but a large part of phenotypic plasticity also stems from environmentally driven transcriptional, post-transcriptional, translational, post-translational, epigenetic and metabolic regulation. Moreover, regulation of the same gene can have different phenotypic outputs in different environments. Consequently, to explain and understand environment-dependent phenotypic plasticity based on the available genotype variation we have to integrate the analysis of further molecular levels reflecting the complete information flow from the gene to metabolism to phenotype. Interestingly, metabolomics platforms are already more cost-effective than NGS platforms and are decisive for the prediction of nutritional value or stress resistance. Here, we propose three fundamental pillars for future breeding strategies in the framework of Green Systems Biology: (i) combining genome selection with environment-dependent PANOMICS analysis and deep learning to improve prediction accuracy for marker-dependent trait performance; (ii) PANOMICS resolution at subtissue, cellular and subcellular level provides information about fundamental functions of selected markers; (iii) combining PANOMICS with genome editing and speed breeding tools to accelerate and enhance large-scale functional validation of trait-specific precision breeding.

Plant-Microbe Symbiosis: What Has Proteomics Taught Us?

Beneficial microbes have a positive impact on the productivity and fitness of the host plant. A better understanding of the biological impacts and underlying mechanisms by which the host derives these benefits will help to address concerns around global food production and security. The recent development of omics-based technologies has broadened our understanding of the molecular aspects of beneficial plant-microbe symbiosis. Specifically, proteomics has led to the identification and characterization of several novel symbiosis-specific and symbiosis-related proteins and post-translational modifications that play a critical role in mediating symbiotic plant-microbe interactions and have helped assess the underlying molecular aspects of the symbiotic relationship. Integration of proteomic data with other "omics" data can provide valuable information to assess hypotheses regarding the underlying mechanism of symbiosis and help define the factors affecting the outcome of symbiosis. Herein, an update is provided on the current and potential applications of symbiosis-based "omic" approaches to dissect different aspects of symbiotic plant interactions. The application of proteomics, metaproteomics, and secretomics as enabling approaches for the functional analysis of plant-associated microbial communities is also discussed.

Plant stress biology in epigenomic era

Recent progress in "omics" methodologies allow us to gain insight into the complex molecular regulatory networks underlying plant responses to environmental stresses. Among the different genome-wide analysis, epigenomics is the most under-investigated "omic" approach requiring more critical and speculative discussion about approaches, methods and experimental designs. Epigenomics allows us to gain insight into the molecular adaptation of plants in response to environmental stresses. The identification of epigenetic marks transmitted during filial generations enables new theories to be developed on the evolution of living organisms in relation to environmental changes. The molecular mechanisms driving the capacity of plants to memorize a stress and to generate stress-resistant progenies are still unclear and scarcely investigated. The elucidation of these cryptic molecular switches will assist breeders in designing crops characterized by minimally compromised productivity in relation to stresses caused by climate change. The aim of this review is to briefly describe the most uptodate epigenomic approaches, update recent progresses in crop epigenomics in plant stress biology, and to stimulate the discussion of new epigenomic methods and approaches in the new era of "omic" sciences.

Proteomic Analysis of Proteins Responsive to Drought and Low Temperature Stress in a Hard Red Spring Wheat Cultivar

Drought stress is becoming more prevalent with global warming, and has been shown to have large effects on gluten proteins linked to wheat bread making quality. Likewise, low temperature stress can detrimentally affect proteins in wheat. This study was done to determine the differential abundance of high molecular weight (HMW) glutenin proteins in a drought and low temperature stressed high quality hard red spring wheat cultivar (PAN3478), against a control. The treatments were applied in the greenhouse at the soft dough stage. HMW glutenin proteins were extracted from the flour, and were separated by using two-dimensional gel electrophoresis. Protein spots that had p values lower than 0.05 and fold values equal to or greater than 1.2 were considered to be significantly differentially abundant. These proteins were further analyzed by using tandem mass spectrometry. There was a 1.3 to 1.8 fold change in 17 protein spots due to the cold treatment. The drought treatment caused a 1.3 to 3.8 fold change in 19 protein spots. These spots matched either HMW or low molecular weight (LMW) glutenin subunits. In the latter case, the C subunits of LMW glutenins were notably found to be up-regulated under both stress conditions. All the proteins that have been identified can directly influence dough characteristics. Data are available via ProteomeXchange with the identifier PXD017578.

iTRAQ-based quantitative tissue proteomic analysis of differentially expressed proteins (DEPs) in non-transgenic and transgenic soybean seeds

The unintended effects of transgenesis have increased food safety concerns, meriting comprehensive evaluation. Proteomic profiling provides an approach to directly assess the unintended effects. Herein, the isobaric tags for relative and absolute quantitation (iTRAQ) comparative proteomic approach was employed to evaluate proteomic profile differences in seed cotyledons from 4 genetically modified (GM) and 3 natural genotypic soybean lines. Compared with their non-GM parents, there were 67, 61, 13 and 22 differentially expressed proteins (DEPs) in MON87705, MON87701 × MON89788, MON87708, and FG72. Overall, 170 DEPs were identified in the 3 GM soybean lines with the same parents, but 232 DEPs were identified in the 3 natural soybean lines. Thus, the differences in protein expression among the genotypic varieties were greater than those caused by GM. When considering ≥2 replicates, 4 common DEPs (cDEPs) were identified in the 3 different GM soybean lines with the same parents and 6 cDEPs were identified in the 3 natural varieties. However, when considering 3 replicates, no cDEPs were identified. Regardless of whether ≥2 or 3 replicates were considered, no cDEPs were identified among the 4 GM soybean lines. Therefore, no feedback due to GM was observed at the common protein level in this study.

Systems biology of seeds: decoding the secret of biochemical seed factories for nutritional security

Seeds serve as biochemical factories of nutrition, processing, bio-energy and storage related important bio-molecules and act as a delivery system to transmit the genetic information to the next generation. The research pertaining towards delineating the complex system of regulation of genes and pathways related to seed biology and nutrient partitioning is still under infancy. To understand these, it is important to know the genes and pathway(s) involved in the homeostasis of bio-molecules. In recent past with the advent and advancement of modern tools of genomics and genetic engineering, multi-layered 'omics' approaches and high-throughput platforms are being used to discern the genes and proteins involved in various metabolic, and signaling pathways and their regulations for understanding the molecular genetics of biosynthesis and homeostasis of bio-molecules. This can be possible by exploring systems biology approaches via the integration of omics data for understanding the intricacy of seed development and nutrient partitioning. These information can be exploited for the improvement of biologically important chemicals for large-scale production of nutrients and nutraceuticals through pathway engineering and biotechnology. This review article thus describes different omics tools and other branches that are merged to build the most attractive area of research towards establishing the seeds as biochemical factories for human health and nutrition.

Enhanced arsenic tolerance and secondary metabolism by modulation of gene expression and proteome profile in Artemisia annua L. after application of exogenous salicylic acid

This study was designed to investigate the effect of exogenous application of salicylic acid (SA) on proteins pattern and secondary metabolites in arsenic (As) stressed Artemisia annua. A. annua was treated by As 100 μM, SA 100 μM and combined treatment of SA 100 μM + As 100 μM upto 3 days. Significant accumulation of As was observed in roots than shoots at As 100 μM treatment. Under As treatment, oxidative stress was induced as indicated by increased TBARS content. Biomass, carotenoid, flavonoids were enhanced whereas total chlorophyll pigment was reduced under As treatment. Combined treatment of SA 100 μM + As 100 μM was more effective for increment of biomass, total chlorophyll content, and flavonoids as compared to As 100 μM treatment. Protein profiling revealed 20 differentially abundant proteins by 2-DE PAGE and MALDI-TOF-MS analysis. Identified proteins were related to photosynthesis, energy metabolism, transcriptional regulators, secondary metabolism, lipid metabolism, transport proteins and unknown/hypothetical proteins. All identified proteins were significantly increased in abundance under combined treatments of SA 100 μM + As 100 μM. The expression analysis of key genes involved in biosynthesis of lipid metabolism, signal molecule, transcriptional regulators, artemisinin biosynthetic genes, isoprenoids pathway, terpenes and flavonoids pathway were significantly upregulated under combined treatments of SA 100 μM + As 100 μM, suggesting a fine linkage in regulation of primary and secondary metabolism to modulate tolerance capacity and to improve phytoremediation property of A. annua against arsenic toxicity.

Label-free quantitative proteomics analysis of Cytosinpeptidemycin responses in southern rice black-streaked dwarf virus-infected rice

Southern rice black-streaked dwarf virus (SRBSDV), a genus Fijivirus of the family Reoviridae, could result in the significant crop losses because being short of an effective controlling measures. Cytosinpeptidemycin, a microbial pesticides developed by China, displayed a wide antiviral activity against many plant viruses. However, its underlying mechanism remains unclear. In this study, a total of 2321 proteins were identified using label-free proteomics technology. Compared with the treatment of SRBSDV-infected rice, 84 and 207 proteins were detected to be up-regulated and only presented in treatment group of SDBSDV-infected rice pre-treated by Cytosinpeptidemycin, which were partially enriched to stress and defense response, such as pathogenesis-related protein 5 (PR-5), pathogenesis-related protein 10 (PR-10) and heat shock protein (Hsp protein). Meanwhile, the real-time quantitative PCR (RT-qPCR) showed that Cytosinpeptidemycin could also up-regulate some resistance genes, and these results indicated a similar trends with the data of the label-free proteomics. Moreover, Cytosinpeptidemycin could enhance the defense enzymatic activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). These data offer a more comprehensive view about the response of SRBSDV-infected rice triggered by Cytosinpeptidemycin in the level of the proteome, mRNA and enzymatic activity.

Plant Abiotic Stress Proteomics: The Major Factors Determining Alterations in Cellular Proteome

HIGHLIGHTS: Major environmental and genetic factors determining stress-related protein abundance are discussed.Major aspects of protein biological function including protein isoforms and PTMs, cellular localization and protein interactions are discussed.Functional diversity of protein isoforms and PTMs is discussed. Abiotic stresses reveal profound impacts on plant proteomes including alterations in protein relative abundance, cellular localization, post-transcriptional and post-translational modifications (PTMs), protein interactions with other protein partners, and, finally, protein biological functions. The main aim of the present review is to discuss the major factors determining stress-related protein accumulation and their final biological functions. A dynamics of stress response including stress acclimation to altered ambient conditions and recovery after the stress treatment is discussed. The results of proteomic studies aimed at a comparison of stress response in plant genotypes differing in stress adaptability reveal constitutively enhanced levels of several stress-related proteins (protective proteins, chaperones, ROS scavenging- and detoxification-related enzymes) in the tolerant genotypes with respect to the susceptible ones. Tolerant genotypes can efficiently adjust energy metabolism to enhanced needs during stress acclimation. Stress tolerance vs. stress susceptibility are relative terms which can reflect different stress-coping strategies depending on the given stress treatment. The role of differential protein isoforms and PTMs with respect to their biological functions in different physiological constraints (cellular compartments and interacting partners) is discussed. The importance of protein functional studies following high-throughput proteome analyses is presented in a broader context of plant biology. In summary, the manuscript tries to provide an overview of the major factors which have to be considered when interpreting data from proteomic studies on stress-treated plants.

A Proteomic Approach to Investigate the Drought Response in the Orphan Crop Eragrostis tef

The orphan crop, Eragrostis tef, was subjected to controlled drought conditions to observe the physiological parameters and proteins changing in response to dehydration stress. Physiological measurements involving electrolyte leakage, chlorophyll fluorescence and ultra-structural analysis showed tef plants tolerated water loss to 50% relative water content (RWC) before adverse effects in leaf tissues were observed. Proteomic analysis using isobaric tag for relative and absolute quantification (iTRAQ) mass spectrometry and appropriate database searching enabled the detection of 5727 proteins, of which 211 proteins, including a number of spliced variants, were found to be differentially regulated with the imposed stress conditions. Validation of the iTRAQ dataset was done with selected stress-related proteins, fructose-bisphosphate aldolase (FBA) and the protective antioxidant proteins, monodehydroascorbate reductase (MDHAR) and peroxidase (POX). Western blot analyses confirmed protein presence and showed increased protein abundance levels during water deficit while enzymatic activity for FBA, MDHAR and POX increased at selected RWC points. Gene ontology (GO)-term enrichment and analysis revealed terms involved in biotic and abiotic stress response, signaling, transport, cellular homeostasis and pentose metabolic processes, to be enriched in tef upregulated proteins, while terms linked to reactive oxygen species (ROS)-producing processes under water-deficit, such as photosynthesis and associated light harvesting reactions, manganese transport and homeostasis, the synthesis of sugars and cell wall catabolism and modification, to be enriched in tef downregulated proteins.

iTRAQ-based quantitative proteomic analysis in vernalization-treated faba bean (Vicia faba L.)

Vernalization is classically defined as the induction of flowering process by exposure of the plants to a prolonged cold condition. Normally, it is considered as a precondition of flowering. Vicia faba, commonly known as faba bean, belongs to family Fabaceae. It is one of the plant species that has been cultivated in the earliest human settlements. In this study, an iTRAQ-LC-MS/MS-based quantitative proteomic analysis has been conducted to compare the vernalized faba bean seedlings and its corresponding control. In total, 91 proteins from various functional categories were observed to be differentially accumulated in vernalized faba bean seedlings. Subsequent gene ontology analysis indicated that several biological processes or metabolic pathways including photosynthesis and phytic acid metabolism were differentially respond to vernalization in comparison to the control sample. Further investigation revealed that a family of proteins nominated as glycine-rich RNA-binding factor was accumulated in vernalized seedlings, indicating an extra layer of regulation by alternative splicing on transcript abundance in response to vernalization. These findings raise a possibility that these candidate proteins could be important to represent the responsive network under vernalization process. Therefore, we propose that the regulation of vernalization in faba bean not only occurs at the transcriptional level as previously reported, but also at the post-transcriptional level.

Metabolomics for Plant Improvement: Status and Prospects

Post-genomics era has witnessed the development of cutting-edge technologies that have offered cost-efficient and high-throughput ways for molecular characterization of the function of a cell or organism. Large-scale metabolite profiling assays have allowed researchers to access the global data sets of metabolites and the corresponding metabolic pathways in an unprecedented way. Recent efforts in metabolomics have been directed to improve the quality along with a major focus on yield related traits. Importantly, an integration of metabolomics with other approaches such as quantitative genetics, transcriptomics and genetic modification has established its immense relevance to plant improvement. An effective combination of these modern approaches guides researchers to pinpoint the functional gene(s) and the characterization of massive metabolites, in order to prioritize the candidate genes for downstream analyses and ultimately, offering trait specific markers to improve commercially important traits. This in turn will improve the ability of a plant breeder by allowing him to make more informed decisions. Given this, the present review captures the significant leads gained in the past decade in the field of plant metabolomics accompanied by a brief discussion on the current contribution and the future scope of metabolomics to accelerate plant improvement.

Identifying the Genes Regulated by AtWRKY6 Using Comparative Transcript and Proteomic Analysis under Phosphorus Deficiency

Phosphorus (P) is an important mineral nutrient for plant growth and development. Overexpressing AtWRKY6 (35S:WRKY6-9) was more sensitive and wrky6 (wrky6-1) was more resistant under low Pi conditions. To better understand the function of AtWRKY6 under low phosphate stress conditions, we applied two-dimensional gel electrophoresis (2-DE) to analyse differentially expressed proteins in the shoots and roots between wild type, 35S:WRKY6-9 and wrky6-1 after phosphorus deficiency treatment for three days. The results showed 88 differentially abundant protein spots, which were identified between the shoots and roots of 35S:WRKY6-9 and wrky6-1 plants. In addition, 59 differentially expressed proteins were identified in the leaves and roots of 35S:WRKY6-9 plants. After analysis, 9 genes with W-box elements in their promoter sequences were identified in the leaves, while 6 genes with W-box elements in their promoter sequences were identified in the roots. A total of 8 genes were identified as potential target genes according to the quantitative PCR (QPCR) and two dimension difference gel electrophoresis, (2D-DIGE) results, including ATP synthase, gln synthetase, nitrilase, 14-3-3 protein, carbonic anhydrases 2, and tryptophan synthase. These results provide important information concerning the AtWRKY6 regulation network and reveal potential vital target genes of AtWRKY6 under low phosphorus stress. two dimension difference gel electrophoresis, 2D-DIGE.

Salt stress induces changes in the proteomic profile of micropropagated sugarcane shoots

Salt stress is one of the most common stresses in agricultural regions worldwide. In particular, sugarcane is affected by salt stress conditions, and no sugarcane cultivar presently show high productivity accompanied by a tolerance to salt stress. Proteomic analysis allows elucidation of the important pathways involved in responses to various abiotic stresses at the biochemical and molecular levels. Thus, this study aimed to analyse the proteomic effects of salt stress in micropropagated shoots of two sugarcane cultivars (CB38-22 and RB855536) using a label-free proteomic approach. The mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD006075. The RB855536 cultivar is more tolerant to salt stress than CB38-22. A quantitative label-free shotgun proteomic analysis identified 1172 non-redundant proteins, and 1160 of these were observed in both cultivars in the presence or absence of NaCl. Compared with CB38-22, the RB855536 cultivar showed a greater abundance of proteins involved in non-enzymatic antioxidant mechanisms, ion transport, and photosynthesis. Some proteins, such as calcium-dependent protein kinase, photosystem I, phospholipase D, and glyceraldehyde-3-phosphate dehydrogenase, were more abundant in the RB855536 cultivar under salt stress. Our results provide new insights into the response of sugarcane to salt stress, and the changes in the abundance of these proteins might be important for the acquisition of ionic and osmotic homeostasis during exposure to salt stress.

Microbial symbionts affect Pisum sativum proteome and metabolome under Didymella pinodes infection

The long cultivation of field pea led to an enormous diversity which, however, seems to hold just little resistance against the ascochyta blight disease complex. The potential of below ground microbial symbiosis to prime the immune system of Pisum for an upcoming pathogen attack has hitherto received little attention. This study investigates the effect of beneficial microbes on the leaf proteome and metabolome as well as phenotype characteristics of plants in various symbiont interactions (mycorrhiza, rhizobia, co-inoculation, non-symbiotic) after infestation by Didymella pinodes. In healthy plants, mycorrhiza and rhizobia induced changes in RNA metabolism and protein synthesis. Furthermore, metal handling and ROS dampening was affected in all mycorrhiza treatments. The co-inoculation caused the synthesis of stress related proteins with concomitant adjustment of proteins involved in lipid biosynthesis. The plant's disease infection response included hormonal adjustment, ROS scavenging as well as synthesis of proteins related to secondary metabolism. The regulation of the TCA, amino acid and secondary metabolism including the pisatin pathway, was most pronounced in rhizobia associated plants which had the lowest infection rate and the slowest disease progression.

BIOLOGICAL SIGNIFICANCE

A most comprehensive study of the Pisum sativum proteome and metabolome infection response to Didymella pinodes is provided. Several distinct patterns of microbial symbioses on the plant metabolism are presented for the first time. Upon D. pinodes infection, rhizobial symbiosis revealed induced systemic resistance e.g. by an enhanced level of proteins involved in pisatin biosynthesis.

Arbuscular mycorrhizal symbiosis affects the grain proteome of Zea mays: a field study

Maize is one of the most important crops worldwide and is strongly dependent on arbuscular mycorrhiza (AM) fungi, organisms that form a mutualistic association with land plants. In maize, AM symbiosis enhances spike dry weight, spike length, spike circumference, and the dry weight and dimensions of the grain. Notwithstanding its ubiquitous nature, the detailed relationship between AM fungal colonization and plant development is not completely understood. To facilitate a better understanding of the effects of AM fungi on plants, the work reported here assessed the effects of a consortium of AM fungi on the kernel proteome of maize, cultivated in open-field conditions. To our knowledge, this is the first report of the modulation of a plant seed proteome following AM fungal inoculation in the field. Here, it was found that AM fungi modify the maize seed proteome by up-regulating enzymes involved in energetic metabolism, embryo development, nucleotide metabolism, seed storage and stress responses.

Proteomics for exploiting diversity of lupin seed storage proteins and their use as nutraceuticals for health and welfare

Lupins have a variety of both traditional and modern uses. In the last decade, reports assessing the benefits of lupin seed proteins have proliferated and, nowadays, the pharmaceutical industry is interested in lupin proteins for human health. Modern genomics and proteomics have hugely contributed to describing the diversity of lupin storage genes and, above all, proteins. Most of these studies have been centered on few edible lupin species. However, Lupinus genus comprises hundreds of species spread throughout the Old and New Worlds, and these resources have been scarcely explored and exploited. We present here a detailed review of the literature on the potential of lupin seed proteins as nutraceuticals, and the use of -omic tools to analyze seed storage polypeptides in main edible lupins and their diversity at the Lupinus inter- and intra-species level. In this sense, proteomics, more than any other, has been a key approach. Proteomics has shown that lupin seed protein diversity, where post-translational modifications yield a large number of peptide variants with a potential concern in bioactivity, goes far beyond gene diversity. The future extended use of second and third generation proteomics should definitely help to go deeper into coverage and characterization of lupin seed proteome.

BIOLOGICAL SIGNIFICANCE

Some important topics concerning storage proteins from lupin seeds are presented and analyzed in an integrated way in this review. Proteomic approaches have been essential in characterizing lupin seed protein diversity, which goes far beyond gene diversity since the protein level adds to the latter differential proteolytic cleavage of conglutin pro-proteins and a diverse array of glycosylation forms and sites. Proteomics has also proved helpful for screening and studying Lupinus germplasm with the future aim of exploiting and improving food production, quality, and nutritional values.

Involvement of a universal amino acid synthesis impediment in cytoplasmic male sterility in pepper

To explore the mechanisms of pepper (Capsicum annuum L.) cytoplasmic male sterility (CMS), we studied the different maturation processes of sterile and fertile pepper anthers. A paraffin section analysis of the sterile anthers indicated an abnormality of the tapetal layer and an over-vacuolization of the cells. The quantitative proteomics results showed that the expression of histidinol dehydrogenase (HDH), dihydroxy-acid dehydratase (DAD), aspartate aminotransferase (ATAAT), cysteine synthase (CS), delta-1-pyrroline-5-carboxylate synthase (P5CS), and glutamate synthetase (GS) in the amino acid synthesis pathway decreased by more than 1.5-fold. Furthermore, the mRNA and protein expression levels of DAD, ATAAT, CS and P5CS showed a 2- to 16-fold increase in the maintainer line anthers. We also found that most of the amino acid content levels decreased to varying degrees during the anther tapetum period of the sterile line, whereas these levels increased in the maintainer line. The results of our study indicate that during pepper anther development, changes in amino acid synthesis are significant and accompany abnormal tapetum maturity, which is most likely an important cause of male sterility in pepper.

Plant responses to ambient temperature fluctuations and water-limiting conditions: A proteome-wide perspective

BACKGROUND

Every year, environmental stresses such as limited water and nutrient availability, salinity, and temperature fluctuations inflict significant losses on crop yields across the globe. Recently, developments in analytical techniques, e.g. mass spectrometry, have led to great advances towards understanding how plants respond to environmental stresses. These processes are mediated by many molecular pathways and, at least partially, via proteome-environment interactions.

SCOPE OF REVIEW

This review focuses on the current state of knowledge about interactions between the plant proteome and the environment, with a special focus on drought and temperature responses of plant proteome dynamics, and subcellular and organ-specific compartmentalization, in Arabidopsis thaliana and crop species.

MAJOR CONCLUSIONS

Correct plant development under non-optimal conditions requires complex self-protection mechanisms, many of them common to different abiotic stresses. Proteome analyses of plant responses to temperature and drought stresses have revealed an intriguing interplay of modifications, mainly affecting the photosynthetic machinery, carbohydrate metabolism, and ROS activation and scavenging. Imbalances between transcript-level and protein-level regulation observed during adaptation to abiotic stresses suggest that many of the regulatory processes are controlled at translational and post-translational levels; proteomics is thus essential in revealing important regulatory networks.

GENERAL SIGNIFICANCE

Because information from proteomic data extends far beyond what can be deduced from transcriptome analysis, the results of proteome studies have substantially deepened our understanding of stress adaptation in plants; this is clearly a prerequisite for designing strategies to improve the yield and quality of crops grown under unfavorable conditions brought about by ongoing climatic change. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock.

iTRAQ-Based Quantitative Proteomic Analysis of Cotton Roots and Leaves Reveals Pathways Associated with Salt Stress

Salinity is a major abiotic stress that affects plant growth and development. In this study, we performed a proteomic analysis of cotton roots and leaf tissue following exposure to saline stress. 611 and 1477 proteins were differentially expressed in the roots and leaves, respectively. In the roots, 259 (42%) proteins were up-regulated and 352 (58%) were down-regulated. In the leaves, 748 (51%) proteins were up-regulated and 729 (49%) were down-regulated. On the basis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, we concluded that the phenylalanine metabolism and starch and sucrose metabolism were active for energy homeostasis to cope with salt stress in cotton roots. Moreover, photosynthesis, pyruvate metabolism, glycolysis / gluconeogenesis, carbon fixation in photosynthetic organisms and phenylalanine metabolism were inhabited to reduce energy consumption. Characterization of the signaling pathways will help elucidate the mechanism activated by cotton in response to salt stress.

Leaf proteome comparison of two GM common bean varieties and their non-GM counterparts by principal component analysis

BACKGROUND

A genetically modified (GM) common bean event, namely Embrapa 5.1, was approved for commercialization in Brazil. The present work aimed to use principal component analysis (PCA) to compare the proteomic profile of this GM common bean and its non-GM counterpart.

RESULTS

Seedlings from four Brazilian common bean varieties were grown under controlled environmental conditions. Leaf proteomic profiles were analyzed by two-dimensional gel electrophoresis (2DE). First, a comparison among 12 gels from four common bean varieties was performed by PCA using volume percentage of 198 matched spots, presented in all gels. The first two principal components (PC) accounted for 46.8% of total variation. Two groups were clearly separated by the first component: Pérola and GM Pérola from Pontal and GM Pontal. Secondly, another comparison among six gels from the same variety GM and its non-GM counterpart was performed by PCA; in this case it was possible to distinguish GM and non-GM.

CONCLUSION

Separation between leaf proteomic profile of GM common bean variety and its counterpart was observed only when they were compared in pairs. These results showed higher similarity between GM variety and its counterpart than between two common bean varieties. PCA is a useful tool to compare proteomes of GM and non-GM plant varieties.

Proteomics and Metabolomics: Two Emerging Areas for Legume Improvement

The crop legumes such as chickpea, common bean, cowpea, peanut, pigeonpea, soybean, etc. are important sources of nutrition and contribute to a significant amount of biological nitrogen fixation (>20 million tons of fixed nitrogen) in agriculture. However, the production of legumes is constrained due to abiotic and biotic stresses. It is therefore imperative to understand the molecular mechanisms of plant response to different stresses and identify key candidate genes regulating tolerance which can be deployed in breeding programs. The information obtained from transcriptomics has facilitated the identification of candidate genes for the given trait of interest and utilizing them in crop breeding programs to improve stress tolerance. However, the mechanisms of stress tolerance are complex due to the influence of multi-genes and post-transcriptional regulations. Furthermore, stress conditions greatly affect gene expression which in turn causes modifications in the composition of plant proteomes and metabolomes. Therefore, functional genomics involving various proteomics and metabolomics approaches have been obligatory for understanding plant stress tolerance. These approaches have also been found useful to unravel different pathways related to plant and seed development as well as symbiosis. Proteome and metabolome profiling using high-throughput based systems have been extensively applied in the model legume species, Medicago truncatula and Lotus japonicus, as well as in the model crop legume, soybean, to examine stress signaling pathways, cellular and developmental processes and nodule symbiosis. Moreover, the availability of protein reference maps as well as proteomics and metabolomics databases greatly support research and understanding of various biological processes in legumes. Protein-protein interaction techniques, particularly the yeast two-hybrid system have been advantageous for studying symbiosis and stress signaling in legumes. In this review, several studies on proteomics and metabolomics in model and crop legumes have been discussed. Additionally, applications of advanced proteomics and metabolomics approaches have also been included in this review for future applications in legume research. The integration of these "omics" approaches will greatly support the identification of accurate biomarkers in legume smart breeding programs.

Biological Networks Underlying Abiotic Stress Tolerance in Temperate Crops--A Proteomic Perspective

Abiotic stress factors, especially low temperatures, drought, and salinity, represent the major constraints limiting agricultural production in temperate climate. Under the conditions of global climate change, the risk of damaging effects of abiotic stresses on crop production increases. Plant stress response represents an active process aimed at an establishment of novel homeostasis under altered environmental conditions. Proteins play a crucial role in plant stress response since they are directly involved in shaping the final phenotype. In the review, results of proteomic studies focused on stress response of major crops grown in temperate climate including cereals: common wheat (Triticum aestivum), durum wheat (Triticum durum), barley (Hordeum vulgare), maize (Zea mays); leguminous plants: alfalfa (Medicago sativa), soybean (Glycine max), common bean (Phaseolus vulgaris), pea (Pisum sativum); oilseed rape (Brassica napus); potato (Solanum tuberosum); tobacco (Nicotiana tabaccum); tomato (Lycopersicon esculentum); and others, to a wide range of abiotic stresses (cold, drought, salinity, heat, imbalances in mineral nutrition and heavy metals) are summarized. The dynamics of changes in various protein functional groups including signaling and regulatory proteins, transcription factors, proteins involved in protein metabolism, amino acid metabolism, metabolism of several stress-related compounds, proteins with chaperone and protective functions as well as structural proteins (cell wall components, cytoskeleton) are briefly overviewed. Attention is paid to the differences found between differentially tolerant genotypes. In addition, proteomic studies aimed at proteomic investigation of multiple stress factors are discussed. In conclusion, contribution of proteomic studies to understanding the complexity of crop response to abiotic stresses as well as possibilities to identify and utilize protein markers in crop breeding processes are discussed.

Agriproteomics of Bread Wheat: Comparative Proteomics and Network Analyses of Grain Size Variation

Agriproteomics signifies the merging of agriculture research and proteomics systems science and is impacting plant research and societal development. Wheat is a frequently consumed foodstuff, has highly variable grain size that in effect contributes to wheat grain yield and the end-product quality. Very limited information is available on molecular basis of grain size due to complex multifactorial nature of this trait. Here, using liquid chromatography-mass spectrometry, we investigated the proteomics profiles from grains of wheat genotypes, Rye selection 111 (RS111) and Chinese spring (CS), which differ in their size. Significant differences in protein expression were found, including 33 proteins uniquely present in RS111 and 32 only in CS, while 54 proteins were expressed from both genotypes. Among differentially expressed proteins, 22 were upregulated, while 21 proteins were downregulated in RS111 compared to CS. Functional classification revealed their role in energy metabolism, seed storage, stress tolerance and transcription. Further, protein interactive network analysis was performed to predict the targets of identified proteins. Significantly different interactions patterns were observed between these genotypes with detection of proteins such as Cyp450, Sus2, and WRKY that could potentially affect seed size. The present study illustrates the potentials of agriproteomics as a veritable new frontier of plant omics research.

Comparative proteomic and physiological characterisation of two closely related rice genotypes with contrasting responses to salt stress

Salinity is a limiting factor affecting crop growth. We evaluated the responses of a salt-tolerant recombinant inbred rice (Oryza sativa L.) line, FL478, and the salt-sensitive IR29. Seedlings were exposed to salt stress and the growth rate was monitored to decipher the effect of long-term stress. At Day 16, IR29 produced lower shoot biomass than FL478. Significant differences for Na+ and K+ concentrations and Na+ : K+ ratios in roots and shoots were observed between genotypes. Changes in the proteomes of control and salt-stressed plants were analysed, identifying 59 and 39 salt-responsive proteins in roots and leaves, respectively. Proteomic analysis showed greater downregulation of proteins in IR29. In IR29, proteins related to pathways involved in salt tolerance (e.g. oxidative stress response, amino acid biosynthesis, polyamine biosynthesis, the actin cytoskeleton and ion compartmentalisation) changed to combat salinity. We found significant downregulation of proteins related to photosynthetic electron transport in IR29, indicating that photosynthesis was influenced, probably increasing the risk of reactive oxygen species formation. The sensitivity of IR29 might be related to its inability to exclude salt from its transpiration stream, to compartmentalise excess ions and to maintain a healthy photosynthetic apparatus during salt stress, or might be because of the leakiness of its roots, allowing excess salt to enter apoplastically. In FL478, superoxide dismutase, ferredoxin thioredoxin reductase, fibre protein and inorganic pyrophosphatase, which may participate in salt tolerance, increased in abundance. Our analyses provide novel insights into the mechanisms behind salt tolerance and sensitivity in genotypes with close genetic backgrounds.

Comparative proteomics of Bt-transgenic and non-transgenic cotton leaves

Background

As the rapid growth of the commercialized acreage in genetically modified (GM) crops, the unintended effects of GM crops’ biosafety assessment have been given much attention. To investigate whether transgenic events cause unintended effects, comparative proteomics of cotton leaves between the commercial transgenic Bt + CpTI cotton SGK321 (BT) clone and its non-transgenic parental counterpart SY321 wild type (WT) was performed.

Results

Using enzyme linked immunosorbent assay (ELISA), Cry1Ac toxin protein was detected in the BT leaves, while its content was only 0.31 pg/g. By 2-DE, 58 differentially expressed proteins (DEPs) were detected. Among them 35 were identified by MS. These identified DEPs were mainly involved in carbohydrate transport and metabolism, chaperones related to post-translational modification and energy production. Pathway analysis revealed that most of the DEPs were implicated in carbon fixation and photosynthesis, glyoxylate and dicarboxylate metabolism, and oxidative pentose phosphate pathway. Thirteen identified proteins were involved in protein-protein interaction. The protein interactions were mainly involved in photosynthesis and energy metabolite pathway.

Conclusions

Our study demonstrated that exogenous DNA in a host cotton genome can affect the plant growth and photosynthesis. Although some unintended variations of proteins were found between BT and WT cotton, no toxic proteins or allergens were detected. This study verified genetically modified operation did not sharply alter cotton leaf proteome, and the target proteins were hardly checked by traditional proteomic analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-015-0071-8) contains supplementary material, which is available to authorized users.

Genetic diversity in tef [Eragrostis tef (Zucc.) Trotter]

Tef [Eragrostis tef (Zucc.) Trotter] is a cereal crop resilient to adverse climatic and soil conditions, and possessing desirable storage properties. Although tef provides high quality food and grows under marginal conditions unsuitable for other cereals, it is considered to be an orphan crop because it has benefited little from genetic improvement. Hence, unlike other cereals such as maize and wheat, the productivity of tef is extremely low. In spite of the low productivity, tef is widely cultivated by over six million small-scale farmers in Ethiopia where it is annually grown on more than three million hectares of land, accounting for over 30% of the total cereal acreage. Tef, a tetraploid with 40 chromosomes (2n = 4x = 40), belongs to the family Poaceae and, together with finger millet (Eleusine coracana Gaerth.), to the subfamily Chloridoideae. It was originated and domesticated in Ethiopia. There are about 350 Eragrostis species of which E. tef is the only species cultivated for human consumption. At the present time, the gene bank in Ethiopia holds over five thousand tef accessions collected from geographical regions diverse in terms of climate and elevation. These germplasm accessions appear to have huge variability with regard to key agronomic and nutritional traits. In order to properly utilize the variability in developing new tef cultivars, various techniques have been implemented to catalog the extent and unravel the patterns of genetic diversity. In this review, we show some recent initiatives investigating the diversity of tef using genomics, transcriptomics and proteomics and discuss the prospect of these efforts in providing molecular resources that can aid modern tef breeding.

Fourteen years of plant proteomics reflected in Proteomics: moving from model species and 2DE-based approaches to orphan species and gel-free platforms

In this article, the topic of plant proteomics is reviewed based on related papers published in the journal Proteomics since publication of the first issue in 2001. In total, around 300 original papers and 41 reviews published in Proteomics between 2000 and 2014 have been surveyed. Our main objective for this review is to help bridge the gap between plant biologists and proteomics technologists, two often very separate groups. Over the past years a number of reviews on plant proteomics have been published . To avoid repetition we have focused on more recent literature published after 2010, and have chosen to rather make continuous reference to older publications. The use of the latest proteomics techniques and their integration with other approaches in the "systems biology" direction are discussed more in detail. Finally we comment on the recent history, state of the art, and future directions of plant proteomics, using publications in Proteomics to illustrate the progress in the field. The review is organized into two major blocks, the first devoted to provide an overview of experimental systems (plants, plant organs, biological processes) and the second one to the methodology.

Wheat proteomics: proteome modulation and abiotic stress acclimation

Cellular mechanisms of stress sensing and signaling represent the initial plant responses to adverse conditions. The development of high-throughput "Omics" techniques has initiated a new era of the study of plant molecular strategies for adapting to environmental changes. However, the elucidation of stress adaptation mechanisms in plants requires the accurate isolation and characterization of stress-responsive proteins. Because the functional part of the genome, namely the proteins and their post-translational modifications, are critical for plant stress responses, proteomic studies provide comprehensive information about the fine-tuning of cellular pathways that primarily involved in stress mitigation. This review summarizes the major proteomic findings related to alterations in the wheat proteomic profile in response to abiotic stresses. Moreover, the strengths and weaknesses of different sample preparation techniques, including subcellular protein extraction protocols, are discussed in detail. The continued development of proteomic approaches in combination with rapidly evolving bioinformatics tools and interactive databases will facilitate understanding of the plant mechanisms underlying stress tolerance.

Understanding the complex nature of salinity and drought-stress response in cereals using proteomics technologies

Worldwide, crop productivity is drastically reduced by drought and salinity stresses. In order to develop food crops with increased productivity in marginal areas, it is important to first understand the nature of plant stress response mechanisms. In the past decade, proteomics tools have been extensively used in the study of plants' proteome responses under experimental conditions mimicking drought and salinity stresses. A lot of proteomic data have been generated using different experimental designs. However, the precise roles of these proteins in stress tolerance are yet to be elucidated. This review summarises the applications of proteomics in understanding the complex nature of drought and salinity stress effects on plants, particularly cereals and also highlights the usefulness of sorghum as the next logical model crop for use in understanding drought and salinity tolerance in cereals. With the vast amount of proteomic data that have been generated to date, a call for integrated efforts across the agricultural, biotechnology, and molecular biology sectors is also highlighted in an effort to translate proteomics data into increased food productivity for the world's growing population.

Elucidation of salt stress defense and tolerance mechanisms of crop plants using proteomics--current achievements and perspectives

Salinity is a major threat limiting the productivity of crop plants. A clear demand for improving the salinity tolerance of the major crop plants is imposed by the rapidly growing world population. This review summarizes the achievements of proteomic studies to elucidate the response mechanisms of selected model and crop plants to cope with salinity stress. We also aim at identifying research areas, which deserve increased attention in future proteome studies, as a prerequisite to identify novel targets for breeding strategies. Such areas include the impact of plant-microbial communities on the salinity tolerance of crops under field conditions, the importance of hormone signaling in abiotic stress tolerance, and the significance of control mechanisms underlying the observed changes in the proteome patterns. We briefly highlight the impact of novel tools for future proteome studies and argue for the use of integrated approaches. The evaluation of genetic resources by means of novel automated phenotyping facilities will have a large impact on the application of proteomics especially in combination with metabolomics or transcriptomics.

Proteomics in the fruit tree science arena: new insights into fruit defense, development, and ripening

Fruit tree crops are agricultural commodities of high economic importance, while fruits also represent one of the most vital components of the human diet. Therefore, a great effort has been made to understand the molecular mechanisms covering fundamental biological processes in fruit tree physiology and fruit biology. Thanks to the development of cutting-edge "omics" technologies such as proteomic analysis, scientists now have powerful tools to support traditional fruit tree research. Such proteomic analyses are establishing high-density 2DE reference maps and peptide mass fingerprint databases that can lead fruit science into a new postgenomic research era. Here, an overview of the application of proteomics in key aspects of fruit tree physiology as well as in fruit biology, including defense responses to abiotic and biotic stress factors, is presented. A panoramic view of ripening-related proteins is also discussed, as an example of proteomic application in fruit science.

Universal sample preparation method integrating trichloroacetic acid/acetone precipitation with phenol extraction for crop proteomic analysis

Crop plants contain large amounts of secondary compounds that interfere with protein extraction and gel-based proteomic analysis. Thus, a protein extraction protocol that can be easily applied to various crop materials with minimal optimization is essential. Here we describe a universal protocol for total protein extraction involving trichloroacetic acid (TCA)/acetone precipitation followed by SDS and phenol extraction. Through SDS extraction, the proteins precipitated by the TCA/acetone treatment can be fully resolubilized and then further purified by phenol extraction. This protocol combines TCA/acetone precipitation, which aggressively removes nonprotein compounds, and phenol extraction, which selectively dissolves proteins, resulting in effective purification of proteins from crop tissues. This protocol can also produce high-quality protein preparations from various recalcitrant tissues, and therefore it has a wide range of applications in crop proteomic analysis. Designed to run on a small scale, this protocol can be completed within 5 h.

Plant proteomics: from genome sequencing to proteome databases and repositories

Proteomic approaches are useful for the identification of functional proteins. These have been enhanced not only by the development of proteomic techniques but also in concert with genome sequencing. In this chapter, 30 databases and Web sites relating to plant proteomics are reviewed and recent technologies relating to data collection and annotation are surveyed.

Transgenic soybeans and soybean protein analysis: an overview

To meet the increasing global demand for soybeans for food and feed consumption, new high-yield varieties with improved quality traits are needed. To ensure the safety of the crop, it is important to determine the variation in seed proteins along with unintended changes that may occur in the crop as a result various stress stimuli, breeding, and genetic modification. Understanding the variation of seed proteins in the wild and cultivated soybean cultivars is useful for determining unintended protein expression in new varieties of soybeans. Proteomic technology is useful to analyze protein variation due to various stimuli. This short review discusses transgenic soybeans, different soybean proteins, and the approaches used for protein analysis. The characterization of soybean protein will be useful for researchers, nutrition professionals, and regulatory agencies dealing with soy-derived food products.