Heterosis profile of sunflower leaves: A label free proteomics approach

Sunflower Hybrids and Inbred Lines Adopt Different Physiological Strategies and Proteome Responses to Cope with Water Deficit

Sunflower is a hybrid crop that is considered moderately drought-tolerant and adapted to new cropping systems required for the agro-ecological transition. Here, we studied the impact of hybridity status (hybrids vs. inbred lines) on the responses to drought at the molecular and eco-physiological level exploiting publicly available datasets. Eco-physiological traits and leaf proteomes were measured in eight inbred lines and their sixteen hybrids grown in the high-throughput phenotyping platform Phenotoul-Heliaphen. Hybrids and parental lines showed different growth strategies: hybrids grew faster in the absence of water constraint and arrested their growth more abruptly than inbred lines when subjected to water deficit. We identified 471 differentially accumulated proteins, of which 256 were regulated by drought. The amplitude of up- and downregulations was greater in hybrids than in inbred lines. Our results show that hybrids respond more strongly to water deficit at the molecular and eco-physiological levels. Because of presence/absence polymorphism, hybrids potentially contain more genes than their parental inbred lines. We propose that detrimental homozygous mutations and the lower number of genes in inbred lines lead to a constitutive defense mechanism that may explain the lower growth of inbred lines under well-watered conditions and their lower reactivity to water deficit.

New hydrophilic material based on hydrogel polymer for the selective enrichment of intact glycopeptides from serum protein digests

The paper describes the preparation and characterization of a new HILIC material for the enrichment of N-linked glycopeptides. The material was prepared using 2-acrylamido-2-methyl-1-propanesulfonic acid as the monomer and ethylene glycol dimethacrylate as the cross-linker. The material was developed by a Box-Behnken experimental design, taking into consideration the amount of monomer-to-crosslinker ratio, the composition, and the amount of porogen mixture. By this approach, the property of the resulting polymer could be fine-tuned to modulate the hydrophilicity and porosity. As HILIC enrichment is mostly dependent on hydrophilic interactions, including H-bonding, the amount of swelling was expected to have an important function, therefore the optimization considered a monomer percent in the range of 20-80%, which implied very different water swelling capacities. After assessing the potential of this new polymer family on fetuin digests, the 17 materials resulting from the Box-Behnken experimental design were used for the enrichment of glycopeptides from serum protein digests. The materials displayed a superior performance over cotton HILIC enrichment, both in terms of the number of enriched N-linked glycopeptides and selectivity, providing up to 762 N-linked glycopeptides with 77% selectivity. The optimization indicated that a high amount of monomer significantly affected the number of enriched glycopeptides, which is also closely connected with the hydrogel nature of the resulting polymers. The results not only provide one additional HILIC material for the enrichment of glycopeptides but also pave the way for the use and development of hydrogel materials for the enrichment of N-linked glycopeptides.

Genetic Improvement in Sunflower Breeding—Integrated Omics Approach

Foresight in climate change and the challenges ahead requires a systematic approach to sunflower breeding that will encompass all available technologies. There is a great scarcity of desirable genetic variation, which is in fact undiscovered because it has not been sufficiently researched as detection and designing favorable genetic variation largely depends on thorough genome sequencing through broad and deep resequencing. Basic exploration of genomes is insufficient to find insight about important physiological and molecular mechanisms unique to crops. That is why integrating information from genomics, epigenomics, transcriptomics, proteomics, metabolomics and phenomics enables a comprehensive understanding of the molecular mechanisms in the background of architecture of many important quantitative traits. Omics technologies offer novel possibilities for deciphering the complex pathways and molecular profiling through the level of systems biology and can provide important answers that can be utilized for more efficient breeding of sunflower. In this review, we present omics profiling approaches in order to address their possibilities and usefulness as a potential breeding tools in sunflower genetic improvement.

Techniques, perspectives, and challenges of bioactive peptide generation: A comprehensive systematic review

Due to the digestible refractory and absorbable structures of bioactive peptides (BPs), they could induce notable biological impacts on the living organism. In this regard, the current study was devoted to providing an overview regarding the available methods for BPs generation by the aid of a systematic review conducted on the published articles up to April 2019. In this context, the PubMed and Scopus databases were screened to retrieve the related publications. According to the results, although the characterization of BPs mainly has been performed using enzymatic and microbial in-vitro methods, they cannot be considered as suitable techniques for further stimulation of digestion in the gastrointestinal tract. Therefore, new approaches for both in-vivo and in-silico methods for BPs identification should be developed to overcome the obstacles that belonged to the current methods. The purpose of this review was to compile the recent analytical methods applied for studying various aspects of food-derived biopeptides, and emphasizing generation at in vitro, in vivo, and in silico.

MicroRNA transcriptomic analysis of the sixth leaf of maize (Zea mays L.) revealed a regulatory mechanism of jointing stage heterosis

BACKGROUND

Zhengdan 958 (Zheng 58 × Chang 7-2), a commercial hybrid that is produced in a large area in China, is the result of the successful use of the heterotic pattern of Reid × Tang-SPT. The jointing stage of maize is the key period from vegetative to reproductive growth, which determines development at later stages and heterosis to a certain degree. MicroRNAs (miRNAs) play vital roles in the regulation of plant development, but how they function in the sixth leaf at the six-leaf (V6) stage to influence jointing stage heterosis is still unclear.

RESULT

Our objective was to study miRNAs in four hybrid combinations developed in accordance with the Reid × Tang-SPT pattern, Zhengdan 958, Anyu 5 (Ye 478 × Chang 7-2), Ye 478 × Huangzaosi, Zheng 58 × Huangzaosi, and their parental inbred lines to explore the mechanism related to heterosis. A total of 234 miRNAs were identified in the sixth leaf at the V6 stage, and 85 miRNAs were differentially expressed between the hybrid combinations and their parental inbred lines. Most of the differentially expressed miRNAs were non-additively expressed, which indicates that miRNAs may participate in heterosis at the jointing stage. miR164, miR1432 and miR528 families were repressed in the four hybrid combinations, and some miRNAs, such as miR156, miR399, and miR395 families, exhibited different expression trends in different hybrid combinations, which may result in varying effects on the heterosis regulatory mechanism.

CONCLUSIONS

The potential targets of the identified miRNAs are related to photosynthesis, the response to plant hormones, and nutrient use. Different hybrid combinations employ different mature miRNAs of the same miRNA family and exhibit different expression trends that may result in enhanced or repressed gene expression to regulate heterosis. Taken together, our results reveal a miRNA-mediated network that plays a key role in jointing stage heterosis via posttranscriptional regulation.

Transcriptomics and proteomics-based analysis of heterosis on main economic traits of silkworm, Bombyx mori

The application of silkworm hybrids have promoted the innovation and development of agricultural technology, but the mechanism of heterosis in silkworm has not been explained clearly. In this study, the heterosis of silkworm in the aspects of body weight, silk gland and cocoon weight was investigated by means of silkworm hybridization and multi-omics approaches, including transcriptome and proteome. The results showed that heterosis of silkworm body weight, silk gland and cocoon weight was overdominant, but only part of genes and proteins were overdominant, and most of genes and proteins were non-additive. Combined analysis obtained six up-regulated genes and four down-regulated genes that were consistent both in transcriptome and proteome. Gene functional enrichment analysis indicated that most up-regulated genes and proteins were mostly related to metabolism, which led to accelerated metabolism and protein synthesis and contributing to improved heterosis. The up-regulation of 6-phosphate glucose dehydrogenase (G6PDH), phosphatidylethanolamine-binding protein (PEBP) and sHSP20.4, which are involved in metabolism, might be related to silk gland heterosis. SIGNIFICANCE: A combination of transcriptomic and proteomic analysis was used to understand the molecular mechanism of silkworm heterosis. We found that the phenotypic traits of silkworm are overdominant, while the analysis of transcriptome and proteome showed that only part of genes and proteins were overdominant, and most of genes and proteins were non-additive. Some of the genes had unique expression in F1, which was speculated that genes under heterozygous condition may result in rearrangement and cause metabolic changes in the hybrids. Those both up-regulated in transcriptomic and proteomic analysis were found to be involved in various metabolic processes, so as to accelerate metabolism and protein synthesis, thus exhibiting heterosis.

Simulation of heterosis in a genome-scale metabolic network provides mechanistic explanations for increased biomass production rates in hybrid plants

Heterosis, or hybrid vigour, is said to occur when F1 individuals exhibit increased performance for a number of traits compared to their parental lines. Improved traits can include increased size, better yield, faster development and a higher tolerance to pathogens or adverse conditions. The molecular basis for the phenomenon remains disputed, despite many decades of theorising and experimentation. In this study, we add a genetics layer to a constraint-based model of plant (Arabidopsis) primary metabolism and show that we can realistically reproduce and quantify heterosis in a highly complex trait (the rate of biomass production). The results demonstrate that additive effects coupled to the complex patterns of epistasis generated by a large metabolic network are sufficient to explain most or all the heterosis seen in typical F1 hybrids. Such models provide a simple approach to exploring and understanding heterosis and should assist in designing breeding strategies to exploit this phenomenon in the future.

Enhanced Nicotiana benthamiana immune responses caused by heterologous plant genes from Pinellia ternata

BACKGROUND

Pinellia ternata is a Chinese traditional medicinal herb, used to cure diseases including insomnia, eclampsia and cervical carcinoma, for hundreds of years. Non-self-recognition in multicellular organisms can initiate the innate immunity to avoid the invasion of pathogens. A design for pathogen independent, heterosis based, fresh resistance can be generated in F1 hybrid was proposed.

RESULTS

By library functional screening, we found that P. ternata genes, named as ptHR375 and ptHR941, were identified with the potential to trigger a hypersensitive response in Nicotiana benthamiana. Significant induction of ROS and Callose deposition in N. benthamiana leaves along with activation of pathogenesis-related genes viz.; PR-1a, PR-5, PDF1.2, NPR1, PAL, RBOHB and ERF1 and antioxidant enzymes was observed. After transformation into N. benthamiana, expression of pathogenesis related genes was significantly up-regulated to generate high level of resistance against Phytophthora capsici without affecting the normal seed germination and morphological characters of the transformed N. benthamiana. UPLC-QTOF-MS analysis of ptHR375 transformed N. benthamiana revealed the induction of Oxytetracycline, Cuelure, Allantoin, Diethylstilbestrol and 1,2-Benzisothiazol-3(2H)-one as bioactive compounds. Here we also proved that F1 hybrids, produced by crossing of the ptHR375 and ptHR941 transformed and non-transformed N. benthamiana, show significant high levels of PR-gene expressions and pathogen resistance.

CONCLUSIONS

Heterologous plant genes can activate disease resistance in another plant species and furthermore, by generating F1 hybrids, fresh pathogen independent plant immunity can be obtained. It is also concluded that ptHR375 and ptHR941 play their role in SA and JA/ET defense pathways to activate the resistance against invading pathogens.

Differentially abundant proteins associated with heterosis in the primary roots of popcorn

Although heterosis has significantly contributed to increases in worldwide crop production, the molecular mechanisms regulating this phenomenon are still unknown. In the present study, we used a comparative proteomic approach to explore hybrid vigor via the proteome of both the popcorn L54 ♀ and P8 ♂ genotypes and the resultant UENF/UEM01 hybrid cross. To analyze the differentially abundant proteins involved in heterosis, we used the primary roots of these genotypes to analyze growth parameters and extract proteins. The results of the growth parameter analysis showed that the mid- and best-parent heterosis were positive for root length and root dry matter but negative for root fresh matter, seedling fresh matter, and protein content. The comparative proteomic analysis identified 1343 proteins in the primary roots of hybrid UENF/UEM01 and its parental lines; 220 proteins were differentially regulated in terms of protein abundance. The mass spectrometry proteomic data are available via ProteomeXchange with identifier “PXD009436”. A total of 62 regulated proteins were classified as nonadditive, of which 53.2% were classified as high parent abundance (+), 17.8% as above-high parent abundance (+ +), 16.1% as below-low parent abundance (− −), and 12.9% as low parent abundance (-). A total of 22 biological processes were associated with nonadditive proteins; processes involving translation, ribosome biogenesis, and energy-related metabolism represented 45.2% of the nonadditive proteins. Our results suggest that heterosis in the popcorn hybrid UENF/UEM01 at an early stage of plant development is associated with an up-regulation of proteins related to synthesis and energy metabolism.

Recent trends and analytical challenges in plant bioactive peptide separation, identification and validation

Interest in research into bioactive peptides (BPs) is growing because of their health-promoting ability. Several bioactivities have been ascribed to peptides, including antioxidant, antihypertensive and antimicrobial properties. As they can be produced from precursor proteins, the investigation of BPs in foods is becoming increasingly popular. For the same reason, production of BPs from by-products has also emerged as a possible means of reducing waste and recovering value-added compounds suitable for functional food production and supplements. Milk, meat and fish are the most investigated sources of BPs, but vegetable-derived peptides are also of interest. Vegetables are commonly consumed, and agro-industrial wastes constitute a cheap, large and lower environmental impact source of proteins. The use of advanced analytical techniques for separation and identification of peptides would greatly benefit the discovery of new BPs. In this context, this review provides an overview of the most recent applications in BP investigations for vegetable food and by-products. The most important issues regarding peptide isolation and separation, by single or multiple chromatographic techniques, are discussed. Additionally, problems connected with peptide identification in plants and non-model plants are discussed regarding the particular case of BP identification. Finally, the issue of peptide validation to confirm sequence and bioactivity is presented. Graphical representation of the analytical workflow needed for investigation of bioactive peptides and applied to vegetables and vegetable wastes Graphical Abstract.

Sunflower Hybrid Breeding: From Markers to Genomic Selection

In sunflower, molecular markers for simple traits as, e.g., fertility restoration, high oleic acid content, herbicide tolerance or resistances to Plasmopara halstedii, Puccinia helianthi, or Orobanche cumana have been successfully used in marker-assisted breeding programs for years. However, agronomically important complex quantitative traits like yield, heterosis, drought tolerance, oil content or selection for disease resistance, e.g., against Sclerotinia sclerotiorum have been challenging and will require genome-wide approaches. Plant genetic resources for sunflower are being collected and conserved worldwide that represent valuable resources to study complex traits. Sunflower association panels provide the basis for genome-wide association studies, overcoming disadvantages of biparental populations. Advances in technologies and the availability of the sunflower genome sequence made novel approaches on the whole genome level possible. Genotype-by-sequencing, and whole genome sequencing based on next generation sequencing technologies facilitated the production of large amounts of SNP markers for high density maps as well as SNP arrays and allowed genome-wide association studies and genomic selection in sunflower. Genome wide or candidate gene based association studies have been performed for traits like branching, flowering time, resistance to Sclerotinia head and stalk rot. First steps in genomic selection with regard to hybrid performance and hybrid oil content have shown that genomic selection can successfully address complex quantitative traits in sunflower and will help to speed up sunflower breeding programs in the future. To make sunflower more competitive toward other oil crops higher levels of resistance against pathogens and better yield performance are required. In addition, optimizing plant architecture toward a more complex growth type for higher plant densities has the potential to considerably increase yields per hectare. Integrative approaches combining omic technologies (genomics, transcriptomics, proteomics, metabolomics and phenomics) using bioinformatic tools will facilitate the identification of target genes and markers for complex traits and will give a better insight into the mechanisms behind the traits.

The disadvantages of being a hybrid during drought: A combined analysis of plant morphology, physiology and leaf proteome in maize

A comparative analysis of various parameters that characterize plant morphology, growth, water status, photosynthesis, cell damage, and antioxidative and osmoprotective systems together with an iTRAQ analysis of the leaf proteome was performed in two inbred lines of maize (Zea mays L.) differing in drought susceptibility and their reciprocal F1 hybrids. The aim of this study was to dissect the parent-hybrid relationships to better understand the mechanisms of the heterotic effect and its potential association with the stress response. The results clearly showed that the four examined genotypes have completely different strategies for coping with limited water availability and that the inherent properties of the F1 hybrids, i.e. positive heterosis in morphological parameters (or, more generally, a larger plant body) becomes a distinct disadvantage when the water supply is limited. However, although a greater loss of photosynthetic efficiency was an inherent disadvantage, the precise causes and consequences of the original predisposition towards faster growth and biomass accumulation differed even between reciprocal hybrids. Both maternal and paternal parents could be imitated by their progeny in some aspects of the drought response (e.g., the absence of general protein down-regulation, changes in the levels of some carbon fixation or other photosynthetic proteins). Nevertheless, other features (e.g., dehydrin or light-harvesting protein contents, reduced chloroplast proteosynthesis) were quite unique to a particular hybrid. Our study also confirmed that the strategy for leaving stomata open even when the water supply is limited (coupled to a smaller body size and some other physiological properties), observed in one of our inbred lines, is associated with drought-resistance not only during mild drought (as we showed previously) but also during more severe drought conditions.

Phenotypic, histological and proteomic analyses reveal multiple differences associated with chloroplast development in yellow and variegated variants from Camellia sinensis

Leaf colour variation is observed in several plants. We obtained two types of branches with yellow and variegated leaves from Camellia sinensis. To reveal the mechanisms that underlie the leaf colour variations, combined morphological, histological, ionomic and proteomic analyses were performed using leaves from abnormal branches (variants) and normal branches (CKs). The measurement of the CIE-Lab coordinates showed that the brightness and yellowness of the variants were more intense than the CKs. When chloroplast profiles were analysed, HY1 (branch with yellow leaves) and HY2 (branch with variegated leaves) displayed abnormal chloroplast structures and a reduced number and size compared with the CKs, indicating that the abnormal chloroplast development might be tightly linked to the leaf colour variations. Moreover, the concentration of elemental minerals was different between the variants and the CKs. Furthermore, DEPs (differentially expressed proteins) were identified in the variants and the CKs by a quantitative proteomics analysis using the label-free approach. The DEPs were significantly involved in photosynthesis and included PSI, PSII, cytochrome b6/f complex, photosynthetic electron transport, LHC and F-type ATPase. Our results suggested that a decrease in the abundance of photosynthetic proteins might be associated with the changes of leaf colours in tea plants.

Proteomic analysis of heterosis in the leaves of sorghum-sudangrass hybrids

Sorghum-sudangrass hybrids are widely used for forage and silage in the animal husbandry industry due to their hardiness. The heterozygous first generation of sorghum-sudangrass hybrids displays performance superior to their homozygous, parental inbred lines. In order to study the molecular details underlying its heterosis, the leaves of sorghum-sudangrass hybrids and their parents were compared using mass spectrometry-based proteomics. Results showed that among the 996 proteins that were identified, 32 proteins showed 'additive accumulation expression patterns', indicating that the protein abundance in sorghum-sudangrass hybrids showed no significant difference from the average of their parents. Additionally, 74 proteins showed 'nonadditive accumulation expression patterns' (the proteins abundance in the hybrids showed significant difference from the average of their parents). Both additive and nonadditive proteins were mainly involved in photosynthesis and carbohydrate metabolism. More upregulated additive and nonadditive proteins were in the hybrids than in their parents, suggesting that additive and nonadditive proteins are essential to the vigor of sorghum-sudangrass hybrids. The nonadditive proteins were enriched in photosynthesis, carbohydrate metabolism, and protein oligomerization, but the additive proteins were not enriched in any pathway, which indicated that the nonadditive proteins could be greater contributors to heterosis than additive proteins. Furthermore, the highly activated photosynthetic pathway in nonadditive proteins implies that photosynthesis in hybrids is heightened to assimilate more organic matter, resulting in an increased yield. Our results provide a proof-of-concept that reveals the molecular components of heterosis in sorghum-sudangrass hybrid leaves and serves as an important step for future genetic manipulation of specific proteins to improve the performance of hybrids.

Proteomic patterns associated with heterosis

Heterosis is characterized by higher seed yields, plant biomass or other traits in heterozygotes or hybrids compared with their genetically divergent parents, which are often homozygous. Despite extensive investigation of heterosis and its wide application in crops such as maize, rice, wheat and sorghum, its molecular basis is still enigmatic. In the past century, some pioneers have proposed multigene models referring to the complementation of allelic and gene expression variation, which is likely to be an important contributor to heterosis. In addition, there are potential interactions of epigenetic variation involved in heterosis via novel mechanisms. At the level of gene expression, many recent studies have revealed that the heterosis phenomenon can be deciphered not only at the transcriptional level but also at the proteomic level. This review presents an update on the information supporting the involvement of proteomic patterns in heterosis and a possible future direction of the field. 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.

A Systems Approach to Elucidate Heterosis of Protein Abundances in Yeast

Heterosis is a universal phenomenon that has major implications in evolution and is of tremendous agro-economic value. To study the molecular manifestations of heterosis and to find factors that maximize its strength, we implemented a large-scale proteomic experiment in yeast. We analyzed the inheritance of 1,396 proteins in 55 inter- and intraspecific hybrids obtained from Saccharomyces cerevisiae and S. uvarum that were grown in grape juice at two temperatures. We showed that the proportion of heterotic proteins was highly variable depending on the parental strain and on the temperature considered. For intraspecific hybrids, this proportion was higher at nonoptimal temperature. Unexpectedly, heterosis for protein abundance was strongly biased toward positive values in interspecific hybrids but not in intraspecific hybrids. Computer modeling showed that this observation could be accounted for by assuming concave relationships between protein abundances and their controlling factors, in line with the metabolic model of heterosis. These results point to nonlinear processes that could play a central role in heterosis.

Hierarchical additive effects on heterosis in rice (Oryza sativa L.)

Exploitation of heterosis in crops has contributed greatly to improvement in global food and energy production. In spite of the pervasive importance of heterosis, a complete understanding of its mechanisms has remained elusive. In this study, a small test-crossed rice population was constructed to investigate the formation mechanism of heterosis for 13 traits. The results of the relative mid-parent heterosis and modes of inheritance of all investigated traits demonstrated that additive effects were the foundation of heterosis for complex traits in a hierarchical structure, and multiplicative interactions among the component traits were the framework of heterosis in complex traits. Furthermore, new balances between unit traits and related component traits provided hybrids with the opportunity to achieve an optimal degree of heterosis for complex traits. This study dissected heterosis of both reproductive and vegetative traits from the perspective of hierarchical structure for the first time. Additive multiplicative interactions of component traits were proven to be the origin of heterosis in complex traits. Meanwhile, more attention should be paid to component traits, rather than complex traits, in the process of revealing the mechanism of heterosis.

What is crop heterosis: new insights into an old topic

Heterosis (or hybrid vigor) refers to a natural phenomenon whereby hybrid offspring of genetically diverse individuals out-perform their parents in multiple traits including yield, adaptability and resistances to biotic and abiotic stressors. Innovations in technology and research continue to clarify the mechanisms underlying crop heterosis, however the intrinsic relationship between the biological basis of heterosis remain unclear. In this review, we aim to provide insight into the molecular genetic basis of heterosis by presenting recent advances in the 'omics' of heterosis and the role of non-coding regions, particularly in relation to energy-use efficiency. We propose that future research should focus on integrating the expanding datasets from different species and hybrid combinations, to mine key heterotic genes and unravel interactive 'omics' networks associated with heterosis. Improved understanding of heterosis and the biological basis for its manipulation in agriculture should help to streamline its use in enhancing crop productivity.

Biomarkers in Alzheimer's disease analysis by mass spectrometry-based proteomics

Alzheimer’s disease (AD) is a common chronic and destructive disease. The early diagnosis of AD is difficult, thus the need for clinically applicable biomarkers development is growing rapidly. There are many methods to biomarker discovery and identification. In this review, we aim to summarize Mass spectrometry (MS)-based proteomics studies on AD and discuss thoroughly the methods to identify candidate biomarkers in cerebrospinal fluid (CSF) and blood. This review will also discuss the potential research areas on biomarkers.