Comparative proteomic analysis reveals alterations in development and photosynthesis-related proteins in diploid and triploid rice

Breeding polyploid Populus: progress and perspective

Populus is a genus of 25-30 species of deciduous flowering plants in the family Salicaceae, which are primarily planted in short-rotation planations for producing timber, pulpwood, wooden products as well as bioenergy feedstock; they are also widely planted in agricultural fields and along roadsides as shelter forest belts for windbreak, decoration, and reduction of pollutants and noise. Moreover, their fast-growth and good adaptation to marginal lands enable them to provide some critical ecosystem services at various phytoremediation sites for land restoration and reclaimation. Thanks to their important roles, breeding for fast growing poplar trees has been one of the most important objectives for nearly a century. One of the most demonstrated, documented achievements in this aspect is polyploid breeding, especially triploid breeding. This paper critically reviews the various techniques used in inducing triploid plants, including natural 2n formation, artificial induction of 2n male and female gemmates through chemical or physical treatments, trait characterization of the triploid and tetraploid breeding populations, unveiling the molecular mechanisms underpinning the significantly improved traits, and identification and selection of the best triploid progenies. This review also recapitulated the challenges and strategies facing the future of triploid breeding in Populus, including amelioration of 2n gamete induction techniques and efficiency, selection of the best parents and identification of the best progrenies, utilization of the huge amount of genomic, transcriptomic, proteomic, metabolomic, and other omics data for selecting parents for improving target traits.

Deciphering ploidal levels of Lippia alba by using proteomics

Lippia alba (Mill.) N.E. Brown (Verbenaceae), popularly known as "lemon balm" or "bushy matgrass", is widely used in folk medicine due to its anti-inflammatory, antispasmodic, analgesic, and digestive properties. It was described as an autopolyploid complex with five cytotypes (2n = 30, 38, 45, 60 and 90). To enhance our understanding of the biological variation of the species, we investigated, comparatively, the proteomic profile of all ploidal levels (diploid, aneuploid, triploid, tetraploid, and hexaploid). Leaf proteins were extracted with subsequent separation by two-dimensional electrophoresis, spot analysis, and protein identification by mass spectrometry. By comparing the proteomic profile of diploid accession to the profile of the other ploidal levels we identified differential expression between the analysed spots. We identified 34 proteins with differential expression between the ploidal levels in comparison with the diploid. The identified proteins seem to play relevant roles in the primary metabolism of L. alba suggesting that a specific set of proteins was selected during the polyploidization process, being the triploid the most different one. Given that protein composition can substantially affect the desired therapeutic effect, we posit that further combination of proteomic and metabolomic studies may help to unravel genetic variations and phenotypic profiles in L. alba.

iTRAQ-based quantitative glutelin proteomic analysis reveals differentially expressed proteins in the physiological metabolism process during endosperm development and their impacts on yield and quality in autotetraploid rice

Autotetraploid rice, which is developed through chromosome set doubling using diploid rice, produces high-quality kernels that are rich in storage proteins. However, little information is available about the content of different proteins in autotetraploid rice and their proteomic analysis. The dynamic changes in four storage proteins, namely, albumin, globulin, prolamin, and glutelin, were analyzed in the endosperm of autotetraploid rice (AJNT-4x) and in that of its diploid counterpart (AJNT-2x) for comparison. The contents of the four proteins were all higher during endosperm development in AJNT-4x than in AJNT-2x, but their change and composition were almost the same in the two materials. Then, iTRAQ was employed to analyze the glutelin profiles of AJNT-4x and AJNT-2x at 10 DAF, 15 DAF, and 20 DAF. A total of 1326 proteins were identified in AJNT-4x and AJNT-2x using high-throughput LC-MS/MS. Among the 1326 identified proteins, there were 362 DEPs in AJNT-4x compared with AJNT-2x and 372 DEPs between different developmental stages in AJNT-4x. Eight important upregulated proteins were identified by qRT-PCR, including B8AM24, B8ARJ0, B8AQM6, A2ZCE6, and P37833. Among them, B8AM24 and B8ARJ0 were related to the lysine biosynthesis process. GO enrichment analysis revealed that the critical functions of DEPs exhibited little overlap between the 10, 15, and 20 DAF groups. Endosperm glutelin accumulation was regulated mainly by different DEPs during the early stage, and 15 DAF was a critical regulating point for glutelin accumulation. KEGG pathway analysis showed that ribosomal proteins were significantly higher in AJNT-4x than in AJNT-2x at 10 DAF, and protein processing, biosynthesis, and metabolism of amino acids were higher and more active in AJNT-4x at 15 DAF, while the peroxisome was richer in AJNT-4x at 20 DAF. The PPI network showed that ribosomal proteins gradually decreased with increasing endosperm development. These results provide new insights into dynamic glutelin expression differences during endosperm development in autotetraploid rice, which will aid in the development of rice cultivars with increased yield and improved grain nutritional quality.

The effects of hybridization and genome doubling in plant evolution via allopolyploidy

Polyploidy is a pervasive and recurring phenomenon across the tree of life, which occurred at variable time scales, ecological amplitudes and cell types, and is especially prominent in the evolutionary histories of plants. Importantly, many of the world's most important crops and noxious invasive weeds are recent polyploids. Polyploidy includes two major types, autopolyploidy, referring to doubling of a single species genome, and allopolyploidy referring to doubling of two or more merged genomes via biological hybridization of distinct but related species. The prevalence of both types of polyploidy implies that both genome doubling alone and doubling coupled with hybridization confer selective advantages over their diploid progenitors under specific circumstances. In cases of allopolyploidy, the two events, genome doubling and hybridization, have both advantages and disadvantages. Accumulated studies have established that, in allopolyploidy, some advantage(s) of doubling may compensate for the disadvantage(s) of hybridity and vice versa, although further study is required to validate generality of this trend. Some studies have also revealed a variety of non-Mendelian genetic and genomic consequences induced by doubling and hybridization separately or concertedly in nascent allopolyploidy; however, the significance of which to the immediate establishment and longer-term evolutionary success of allopolyploid species remain to be empirically demonstrated and ecologically investigated. This review aims to summarize recent advances in our understanding of the roles of hybridization and genome doubling, in separation and combination, in the evolution of allopolyploid genomes, as well as fruitful future research directions that are emerging from these studies.

Oxidative stress response and proteomic analysis reveal the mechanisms of toxicity of imidazolium-based ionic liquids against Arabidopsis thaliana

Ionic liquids (ILs) are extensively used in various fields, posing a potential threat in the ecosystem because of their high stability, excellent solubility, and biological toxicity. In this study, the toxicity mechanism of three ILs, 1-octyl-3-methylimidazolium chloride ([C₈MIM]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀MIM]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C₁₂MIM]Cl) on Arabidopsis thaliana were revealed. Reactive oxygen species (ROS) level increased with higher concentration and longer carbon chain length of ILs, which led to the increase of malondialdehyde (MDA) content and antioxidase activity, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and peroxidase (POD) activities. SOD, CAT, and GPX activities decreased in high ILs concentration due to the excessive ROS. Differentially expressed protein was analyzed based on Gene ontology (GO) and KEGG pathways analysis. 70, 45, 84 up-regulated proteins, and 72, 104, 79 down-regulated proteins were identified in [C₈MIM]Cl, [C₁₀MIM]Cl, and [C₁₂MIM]Cl treatment, respectively (fold change ≥ 1.5 with ≥95% confidence). Cellular aldehyde metabolic process, mitochondrial and mitochondrial respiratory chains, glutathione transferase and oxidoreductase activity were enriched as up-regulated proteins as the defense mechanism of A. thaliana to resist external stresses. Chloroplast, photosynthetic membrane and thylakoid, structural constituent of ribosome, and transmembrane transport were enriched as the down-regulated protein. Compared with the control, 8 and 14 KEGG pathways were identified forup-regulated and down-regulated proteins, respectively, in three IL treatments. Metabolic pathways, carbon metabolism, biosynthesis of amino acids, porphyrin and chlorophyll metabolism were significantly down-regulated. The GO terms annotation demonstrated the oxidative stress response and effects on photosynthesis of A. thaliana in ILs treatment from biological process, cellular component, and molecular function categories.

Integrated analysis of quantitative proteome and transcriptional profiles reveals abnormal gene expression and signal pathway in bladder cancer

BACKGROUND

Bladder cancer (BCa) is a tumor associated with high morbidity and mortality and its incidence is increasing worldwide. However, the pathogenesis of bladder cancer is not well understood.

OBJECTIVE

To further illustrate the molecular mechanisms involved in the pathogenesis of BCa and identify potential therapeutic targets, we combined the transcriptomic analysis with RNA sequencing and tandem mass tags (TMT)-based proteomic methods to quantitatively screen the differentially expressed genes and proteins between bladder cancer tissues (BC) and adjacent normal tissues (AN).

RESULTS

Transcriptome and proteome studies indicated 7094 differentially expressed genes (DEGs) and 596 differentially expressed proteins (DEPs) between BC and AN, respectively. GO enrichment analyses revealed that cell adhesion, calcium ion transport, and regulation of ATPase activity were highly enriched in BCa. Moreover, several key signaling pathway were identified as of relevance to BCa, in particular the ECM-receptor interaction, cell adhesion molecules (CAMs), and PPAR signaling pathway. Interestingly, 367 genes were shared by DEGs and DEPs, and a significant positive correlation between mRNA and translation profiles was found.

CONCLUSION

In summary, this joint analysis of transcript and protein profiles provides a comprehensive reference map of gene activity regarding the disease status of BCa.

Cytological and proteomic analyses of floral buds reveal an altered atlas of meiosis in autopolyploid Brassica rapa

Background

Polyploidy is considered as a basic event in plant speciation and evolution in nature, and the cytological and proteomic profilings of floral buds at meiosis (FAM) would definitely contribute to a better understanding of the polyploid-associated effects during plant reproduction cycle.

Results

Herein, the cytological investigations demonstrated that chromosome behaviors such as univalent and multivalent at prophase I, chaotic alignments at metaphase, aberrant segregation at telophase, were frequently observed during meiosis in autotetraploid Brassica rapa. The proteomic analysis showed a total of 562 differentially expressed proteins (DEPs) were identified in FAM between autotetraploid and diploid B. rapa. Notably, PARP2 and LIG1 related to base excision repair and BARD1 involved in recombination were significantly down-regulated in autotetraploid B. rapa, which indicated DNA repair pathway were more likely affected during meiosis in autotetraploid B. rapa. The functional analysis showed that DEPs assigned to “chromatin structure and dynamics”, “cell cycle control, cell division, chromosome partitioning” and “cytoskeleton” were preferentially up-regulated, which suggested a robust regulation of cell division in autotetraploid B. rapa. In combination with the floral RNA-seq data released, a number of DEPs were found positively correlated with their transcript abundance, but posttranslational modification of proteins might also play a role in regulating meiosis course after polyploidization.

Conclusions

In general, this study provides a detailed cytology and proteome landscape of FAM between diploid and autotetraploid B. rapa, which definitely affords us a better understanding of uniformity and discrepancy of meiosis at the plant reproductive stage before and after polyploidization.

Electronic supplementary material

The online version of this article (10.1186/s13578-019-0313-z) contains supplementary material, which is available to authorized users.

Genome-wide proteomic profiling reveals the role of dominance protein expression in heterosis in immature maize ears

Heterosis refers to the phenomenon in which hybrid progeny show superior performance relative to their parents. Early maize ear development shows strong heterosis in ear architecture traits and greatly affects grain yield. To explore the underlying molecular mechanisms, genome-wide proteomics of immature ears of maize hybrid ZD909 and its parents were analyzed using tandem mass tag (TMT) technology. A total of 9,713 proteins were identified in all three genotypes. Among them, 3,752 (38.6%) proteins were differentially expressed between ZD909 and its parents. Multiple modes of protein action were discovered in the hybrid, while dominance expression patterns accounted for 63.6% of the total differentially expressed proteins (DEPs). Protein pathway enrichment analysis revealed that high parent dominance proteins mainly participated in carbon metabolism and nitrogen assimilation processes. Our results suggested that the dominant expression of favorable alleles related to C/N metabolism in the hybrid may be essential for ZD909 ear growth and heterosis formation. Integrated analysis of proteomic and quantitative trait locus (QTL) data further support our DEP identification and provide useful information for the discovery of genes associated with ear development. Our study provides comprehensive insight into the molecular mechanisms underlying heterosis in immature maize ears from a proteomic perspective.

Comparative proteomic analysis of autotetraploid and diploid Paulownia tomentosa reveals proteins associated with superior photosynthetic characteristics and stress adaptability in autotetraploid Paulownia

To enlarge the germplasm resource of Paulownia plants, we used colchicine to induce autotetraploid Paulownia tomentosa, as reported previously. Compared with its diploid progenitor, autotetraploid P. tomentosa exhibits better photosynthetic characteristics and higher stress resistance. However, the underlying mechanism for its predominant characteristics has not been determined at the proteome level. In this study, isobaric tag for relative and absolute quantitation coupled with liquid chromatography-tandem mass spectrometry was employed to compare proteomic changes between autotetraploid and diploid P. tomentosa. A total of 1427 proteins were identified in our study, of which 130 proteins were differentially expressed between autotetraploid and diploid P. tomentosa. Functional analysis of differentially expressed proteins revealed that photosynthesis-related proteins and stress-responsive proteins were significantly enriched among the differentially expressed proteins, suggesting they may be responsible for the photosynthetic characteristics and stress adaptability of autotetraploid P. tomentosa. The correlation analysis between transcriptome and proteome data revealed that only 15 (11.5%) of the differentially expressed proteins had corresponding differentially expressed unigenes between diploid and autotetraploid P. tomentosa. These results indicated that there was a limited correlation between the differentially expressed proteins and the previously reported differentially expressed unigenes. This work provides new clues to better understand the superior traits in autotetraploid P. tomentosa and lays a theoretical foundation for developing Paulownia breeding strategies in the future.

Implications of polyploidy events on the phenotype, microstructure, and proteome of Paulownia australis

Polyploidy events are believed to be responsible for increasing the size of plant organs and enhancing tolerance to environmental stresses. Autotetraploid Paulownia australis plants exhibit superior traits compared with their diploid progenitors. Although some transcriptomics studies have been performed and some relevant genes have been revealed, the molecular and biological mechanisms regulating the predominant characteristics and the effects of polyploidy events on P. australis remain unknown. In this study, we compared the phenotypes, microstructures, and proteomes of autotetraploid and diploid P. australis plants. Compared with the diploid plant, the leaves of the autotetraploid plant were longer and wider, and the upper epidermis, lower epidermis, and palisade layer of the leaves were thicker, the leaf spongy parenchyma layer was thinner, the leaf cell size was bigger, and cell number was lower. In the proteome analysis, 3,010 proteins were identified and quantified, including 773 differentially abundant proteins. These results may help to characterize the P. australis proteome profile. Differentially abundant proteins related to cell division, glutathione metabolism, and the synthesis of cellulose, chlorophyll, and lignin were more abundant in the autotetraploid plants. These results will help to enhance the understanding of variations caused by polyploidy events in P. australis. The quantitative real-time PCR results provided details regarding the expression patterns of the proteins at mRNA level. We observed a limited correlation between transcript and protein levels. These observations may help to clarify the molecular basis for the predominant autotetraploid characteristics and be useful for plant breeding in the future.