Label-free quantitative proteomic analysis of pre-flowering PMeV-infected Carica papaya L

Juvenile-related tolerance to papaya sticky disease (PSD): proteomic, ultrastructural, and physiological events

KEY MESSAGE

The proteomic analysis of PMeV-complex-infected C. papaya unveiled proteins undergoing modulation during the plant's development. The infection notably impacted processes related to photosynthesis and cell wall dynamics. The development of Papaya Sticky Disease (PSD), caused by the papaya meleira virus complex (PMeV-complex), occurs only after the juvenile/adult transition of Carica papaya plants, indicating the presence of tolerance mechanisms during the juvenile development phase. In this study, we quantified 1609 leaf proteins of C. papaya using a label-free strategy. A total of 345 differentially accumulated proteins were identified-38 at 3 months (juvenile), 130 at 4 months (juvenile/adult transition), 160 at 7 months (fruit development), and 17 at 9 months (fruit harvesting)-indicating modulation of biological processes at each developmental phase, primarily related to photosynthesis and cell wall remodeling. Infected 3- and 4-mpg C. papaya exhibited an accumulation of photosynthetic proteins, and chlorophyll fluorescence results suggested enhanced energy flux efficiency in photosystems II and I in these plants. Additionally, 3 and 4-mpg plants showed a reduction in cell wall-degrading enzymes, followed by an accumulation of proteins involved in the synthesis of wall precursors during the 7 and 9-mpg phases. These findings, along with ultrastructural data on laticifers, indicate that C. papaya struggles to maintain the integrity of laticifer walls, ultimately failing to do so after the 4-mpg phase, leading to latex exudation. This supports initiatives for the genetic improvement of C. papaya to enhance resistance against the PMeV-complex.

A Capsid Protein Fragment of a Fusagra-like Virus Found in Carica papaya Latex Interacts with the 50S Ribosomal Protein L17

Papaya sticky disease is caused by the association of a fusagra-like and an umbra-like virus, named papaya meleira virus (PMeV) and papaya meleira virus 2 (PMeV2), respectively. Both viral genomes are encapsidated in particles formed by the PMeV ORF1 product, which has the potential to encode a protein with 1563 amino acids (aa). However, the structural components of the viral capsid are unknown. To characterize the structural proteins of PMeV and PMeV2, virions were purified from Carica papaya latex. SDS-PAGE analysis of purified virus revealed two major proteins of ~40 kDa and ~55 kDa. Amino-terminal sequencing of the ~55 kDa protein and LC-MS/MS of purified virions indicated that this protein starts at aa 263 of the deduced ORF1 product as a result of either degradation or proteolytic processing. A yeast two-hybrid assay was used to identify Arabidopsis proteins interacting with two PMeV ORF1 product fragments (aa 321-670 and 961-1200). The 50S ribosomal protein L17 (AtRPL17) was identified as potentially associated with modulated translation-related proteins. In plant cells, AtRPL17 co-localized and interacted with the PMeV ORF1 fragments. These findings support the hypothesis that the interaction between PMeV/PMeV2 structural proteins and RPL17 is important for virus-host interactions.

Effect of different drying techniques on rose (Rosa rugosa cv. Plena) proteome based on label-free quantitative proteomics

To explore the molecular mechanisms of different processing technologies on rose tea (Rosa rugosa cv. Plena), we investigated the rose tea proteome (fresh rose tea [CS], vacuum freeze-drying rose tea [FD], and vacuum microwave rose tea [VD]) using label-free quantification proteomics (LFQ). A total of 2187 proteins were identified, with 1864, 1905, and 1660 proteins identified in CS, FD, and VD, respectively. Of those, 1500 proteins were quantified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation and enrichment analysis of differential expression proteins (DEPs) in VD vs. CS, FD vs. CS, and FD vs. VD showed that these pathways were associated with energy metabolism, the metabolic breakdown of energy substances and protein biosynthesis, such as oxidative phosphorylation, citrate cycle, carbon metabolism pathways, and ribosome and protein processing in endoplasmic reticulum. FD could ensure the synthesis of protein translation and energy metabolism, thereby maintaining the high quality of rose tea.

Label-free quantitative proteomics analysis of jujube (Ziziphus jujuba Mill.) during different growth stages

Chinese jujube (Zizyphus jujuba Mill.), a member of the Rhamnaceae family with favorable nutritional and flavor quality, exhibited characteristic climacteric changes during its fruit growth stage. Therefore, fruit samples were harvested at four developmental stages on days 55 (young fruits), 76 (white-mature fruits), 96 (half-red fruits), and 116 (full-red fruits) after flowering (DAF). This study then investigated those four growth stage changes of the jujube proteome using label-free quantification proteomics. The results identified 4762 proteins in the samples, of which 3757 proteins were quantified. Compared with former stages, the stages examined were designated as "76 vs. 55 DAF" group, "96 vs. 76 DAF" group, and "116 vs. 96 DAF" group. Gene Ontology (GO) and KEGG annotation and enrichment analysis of the differentially expressed proteins (DEPs) showed that 76 vs. 55 DAF group pathways represented amino sugar, nucleotide sugar, ascorbate, and aldarate metabolic pathways. These pathways were associated with cell division and resistance. In the study, the jujube fruit puffing slowed down and attained a stable growth stage in the 76 vs. 55 DAF group. However, fatty acid biosynthesis and phenylalanine metabolism was mainly enriched in the 96 vs. 76 DAF group. Fatty acids are precursors of aromatic substances and fat-soluble pigments in fruit. The upregulation of differential proteins at this stage indicates that aromatic compounds were synthesized in large quantities at this stage and that fruit would enter the ripening stage. During the ripening stage, 55 DEPs were identified to be involved in photosynthesis and flavonoid biosynthesis in the 116 vs. 96 DAF group. Also, the fruit entered the mature stage, which showed that flavonoids were produced in large quantities. Furthermore, the color of jujube turned red, and photosynthesis was significantly reduced. Hence, a link was established between protein profiles and growth phenotypes, which will help improve our understanding of jujube fruit growth at the proteomic level.

Comparative proteomic analysis of Nicotiana benthamiana plants under Chinese wheat mosaic virus infection

BACKGROUND

Chinese wheat mosaic virus (CWMV) is a severe threat to winter wheat and is transmitted by Polymyxa graminis. The mechanisms of interactions between CWMV and plants are poorly understood. In this study, a comparative proteomics analysis based on nanoliquid chromatography mass spectrometry (MS)/MS was conducted to characterize proteomic changes in plants responding to CWMV infection.

RESULTS

In total, 2751 host proteins were identified, 1496 of which were quantified and 146 up-regulated and 244 down-regulated proteins were identified as differentially expressed proteins (DEPs). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that DEPs were most strongly associated with photosynthesis antenna proteins, MAPK signaling plant and glyoxylate and dicarboxylate metabolism pathways. Subcellular localization analysis predicted that more than half of the DEPs were localized in the chloroplast, an organelle indispensable for abscisic acid (ABA) synthesis. Our results suggest that CWMV infection interrupts normal chloroplast functions and decreases ABA concentrations in Nicotiana benthamiana. Further analysis showed that the ABA pathway was suppressed during CWMV infection and that ABA treatment induced plant hosts defenses against CWMV.

CONCLUSIONS

We identified several candidate proteins expressed during CWMV infection, and the ABA pathway was strongly associated with responses to CWMV infection in N. benthamiana.

Battle of Three: The Curious Case of Papaya Sticky Disease

Among the most serious problems in papaya production are the viruses associated with papaya ringspot and papaya sticky disease (PSD). PSD concerns producers worldwide because its symptoms are extremely aggressive and appear only after flowering. As no resistant cultivar is available, several disease management strategies have been used in affected countries, such as the use of healthy seeds, exclusion of the pathogen, and roguing. In the 1990s, a dsRNA virus, papaya meleira virus (PMeV), was identified in Brazil as the causal agent of PSD. However, in 2016 a second virus, papaya meleira virus 2 (PMeV2), with an ssRNA genome, was also identified in PSD plants. Only PMeV is detected in asymptomatic plants, whereas all symptomatic plants contain both viral RNAs separately packaged in particles formed by the PMeV capsid protein. PSD also affects papaya plants in Mexico, Ecuador, and Australia. PMeV2-like viruses have been identified in the affected plants, but the partner virus(es) in these countries are still unknown. In Brazil, PMeV and PMeV2 reside in laticifers that promote spontaneous latex exudation, resulting in the affected papaya fruit's sticky appearance. Genes modulated in plants affected by PSD include those involved in reactive oxygen species and salicylic acid signaling, proteasomal degradation, and photosynthesis, which are key plant defenses against PMeV complex infection. However, the complete activation of the defense response is impaired by the expression of negative effectors modulated by the virus. This review presents a summary of the current knowledge of the Carica papaya-PMeV complex interaction and management strategies.

Synaptamide activates the adhesion GPCR GPR110 (ADGRF1) through GAIN domain binding

Adhesion G protein-coupled receptors (aGPCR) are characterized by a large extracellular region containing a conserved GPCR-autoproteolysis-inducing (GAIN) domain. Despite their relevance to several disease conditions, we do not understand the molecular mechanism by which aGPCRs are physiologically activated. GPR110 (ADGRF1) was recently deorphanized as the functional receptor of N-docosahexaenoylethanolamine (synaptamide), a potent synaptogenic metabolite of docosahexaenoic acid. Thus far, synaptamide is the first and only small-molecule endogenous ligand of an aGPCR. Here, we demonstrate the molecular basis of synaptamide-induced activation of GPR110 in living cells. Using in-cell chemical cross-linking/mass spectrometry, computational modeling and mutagenesis-assisted functional assays, we discover that synaptamide specifically binds to the interface of GPR110 GAIN subdomains through interactions with residues Q511, N512 and Y513, causing an intracellular conformational change near TM6 that triggers downstream signaling. This ligand-induced GAIN-targeted activation mechanism provides a framework for understanding the physiological function of aGPCRs and therapeutic targeting in the GAIN domain.

Huang et al clarify the molecular mechanism of activation of adhesion G protein-coupled receptor GPR110 by synaptamide, the only small-molecule endogenous ligand known for this class of GPCR. They find through chemical cross-linking mass spectrometry, modeling and mutagenesis that synaptamide binds to residues in the GAIN domain and induces a conformational change triggering downstream signaling.

Next generation sequencing and proteomics in plant virology: how is Colombia doing?

Crop production and trade are two of the most economically important activities in Colombia, and viral diseases cause a high negative impact to agricultural sector. Therefore, the detection, diagnosis, control, and management of viral diseases are crucial. Currently, Next-Generation Sequencing (NGS) and ‘Omic’ technologies constitute a right-hand tool for the discovery of novel viruses and for studying virus-plant interactions. This knowledge allows the development of new viral diagnostic methods and the discovery of key components of infectious processes, which could be used to generate plants resistant to viral infections. Globally, crop sciences are advancing in this direction. In this review, advancements in ‘omic’ technologies and their different applications in plant virology in Colombia are discussed. In addition, bioinformatics pipelines and resources for omics data analyses are presented. Due to their decreasing prices, NGS technologies are becoming an affordable and promising means to explore many phytopathologies affecting a wide variety of Colombian crops so as to improve their trade potential.

Comparative proteomic analysis provides novel insights into the regulation mechanism underlying papaya (Carica papaya L.) exocarp during fruit ripening process

BACKGROUND

Papaya (Carica papaya L.) is a popular climacteric fruit, undergoing various physico-chemical changes during ripening. Although papaya is widely cultivated and consumed, few studies on the changes in metabolism during its ripening process at the proteasome level have been performed. Using a newly developed TMT-LCMS analysis, proteomes of papaya fruit at different ripening stages were investigated.

RESULTS

In total, 3220 proteins were identified, of which 2818 proteins were quantified. The differential accumulated proteins (DAPs) exhibited various biological functions and diverse subcellular localizations. The KEGG enrichment analysis showed that various metabolic pathways were significantly altered, particularly in flavonoid and fatty acid metabolisms. The up-regulation of several flavonoid biosynthesis-related proteins may provide more raw materials for pigment biosynthesis, accelerating the color variation of papaya fruit. Variations in the fatty acid metabolism- and cell wall degradation-related proteins were investigated during the ripening process. Furthermore, the contents of several important fatty acids were determined, and increased unsaturated fatty acids may be associated with papaya fruit volatile formation.

CONCLUSIONS

Our data may give an intrinsic explanation of the variations in metabolism during the ripening process of papaya fruit.