Differential proteomics profiling of the ova between healthy and Rice stripe virus-infected female insects of Laodelphax striatellus

Proteomic analysis of Laodelphax striatellus in response to Rice stripe virus infection reveal a potential role of ZFP36L1 in restriction of viral proliferation

Persistent plant viruses multiply and circulate inside insect vectors following the route of midgut-hemolymph-salivary gland. Currently, how viruses interact with insect vectors after they are released into hemolymph is not entirely clear. In this study, we found that the hemolymph and fat body (HF) contained the highest Rice stripe virus (RSV) levels. Proteomic analysis on RSV-free and RSV-infected HF identified 156 differentially expressed proteins (DEPs), with the majority of them participating in metabolism, transportation, and detoxification. The RNA binding protein esf2 was the most downregulated protein. Knocking down the expression of esf2 did not influence the RSV burden, but caused the lethal effect to L. striatellus. In contrast, the mRNA decay protein ZFP36L1 was 69% more abundant upon RSV infection, and suppression of ZFP36L1 significantly increased the RSV burden. Our results reveal the potential role of ZFP36L1 in restricting the viral proliferation, and provide valuable clues for unravelling the interaction between RSV and L. striatellus in HF. SIGNIFICANCE: More than 76% of plant viruses are transmitted by insect vectors. For persistent propagative transmission, plant viruses multiply and circulate inside insects following the route of midgut-hemolymph-salivary gland. However, how viruses interact with vector insects after they are released into hemolymph is not entirely clear. Our study investigated the influence of rice stripe virus (RSV) on insect hemolymph and fat body by iTRAQ labeling method. Among the 156 differentially expressed proteins (DEPs) identified, two proteins associated with mRNA metabolism were selected for function analysis. We found that the mRNA decay activator protein ZFP36L1 influenced the RSV proliferation, and RNA binding protein esf2 caused the lethal effect to L. striatellus. Our results provide valuable clues for unveiling the interaction between RSV and L. striatellus, and might be useful in pest management.

Insecticidal and synergistic activity of dsRNAs targeting buprofezin-specific genes against the small brown planthopper, Laodelphax striatellus

The small brown planthopper, Laodelphax striatellus, is a dangerous pest in rice fields. Although buprofezin has been used to control L. striatellus for more than a decade, the occurrence of buprofezin-resistant L. striatellus has been recently reported. To develop an alternative pest control strategy, comparative transcriptome analysis of buprofezin-treated and nontreated L. striatellus was performed to screen the buprofezin-specific target genes for RNA interference (RNAi) application. Among six genes downregulated in the buprofezin-treated L. striatellus, RNAi-based silencing of the lipophorin precursor, endocuticle structure glycoprotein, and chitin synthase significantly induced the lethality of L. striatellus in a concentration-dependent manner. In addition, a cocktail of double-stranded RNAs against these three genes showed synergistic effects with buprofezin. These results provide RNAi-based effective approaches to control L. striatellus as well as an efficient method to identify novel target genes for RNAi application.

Comparative iTRAQ proteomic profiling of proteins associated with the adaptation of brown planthopper to moderately resistant vs. susceptible rice varieties

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a destructive pest that poses a significant threat to rice plants worldwide. To explore how BPHs adapt to the resistant rice variety, we analyzed proteomics profiles of two virulent N. lugens populations. We focused on Biotype Y, which can survive on the moderately resistant rice variety YHY15, and Biotype I, which can survive on the susceptible rice variety TN1. We performed protein quantitation using the isobaric tag for relative and absolute quantification (iTRAQ) and then compared the expression patterns between two virulent N. lugens populations and found 258 differentially expressed proteins (DEPs). We found that 151 of the DEPs were up-regulated, while 107 were down-regulated. We evaluated transcript levels of 8 expressed genes from the iTRAQ results by qRT-PCR, which revealed transcriptional changes that were consistent with the changes at the protein level. The determination of the protein changes in two virulent N. lugens populations would help to better understanding BPH adaptation to resistant rice varieties and facilitate the better design of new control strategies for host defense against BPH.

Applications of Proteomic Tools to Study Insect Vector-Plant Virus Interactions

Proteins are crucial players of biological interactions within and between the organisms and thus it is important to understand the role of proteins in successful partnerships, such as insect vectors and their plant viruses. Proteomic approaches have identified several proteins at the interface of virus acquisition and transmission by their insect vectors which could be potential molecular targets for sustainable pest and viral disease management strategies. Here we review the proteomic techniques used to study the interactions of insect vector and plant virus. Our review will focus on the techniques available to identify the infection, global changes at the proteome level in insect vectors, and protein-protein interactions of insect vectors and plant viruses. Furthermore, we also review the integration of other techniques with proteomics and the available bioinformatic tools to analyze the proteomic data.

Suppression of Rice Stripe Virus Replication in Laodelphax striatellus Using Vector Insect-Derived Double-Stranded RNAs

RNA interference (RNAi) has attracted attention as a promising approach to control plant viruses in their insect vectors. In the present study, to suppress replication of the rice stripe virus (RSV) in its vector, Laodelphax striatellus, using RNAi, dsRNAs against L. striatellus genes that are strongly upregulated upon RSV infection were delivered through a rice leaf-mediated method. RNAi-based silencing of peroxiredoxin, cathepsin B, and cytochrome P450 resulted in significant down regulation of the NS3 gene of RSV, achieving a transcriptional reduction greater than 73.6% at a concentration of 100 ng/μl and, possibly compromising viral replication. L. striatellus genes might play crucial roles in the transmission of RSV; transcriptional silencing of these genes could suppress viral replication in L. striatellus. These results suggest effective RNAi-based approaches for controlling RSV and provide insight into RSV-L. striatellus interactions.

High Diversity and Functional Complementation of Alimentary Canal Microbiota Ensure Small Brown Planthopper to Adapt Different Biogeographic Environments

Almost all insects harbor commensal bacteria in the alimentary canal lumen or within cells and often play a pivotal role in their host’s development, evolution, and environmental adaptation. However, little is known about the alimentary canal microbiota and their functions in sap-sucking insect pests of crops, which can damage plants by removing plant sap and by transmitting various plant viruses, especially in the small brown planthopper, Laodelphax striatellus. In this study, we characterized the alimentary canal microbiota of L. striatellus collected from seven regions in China by sequencing 16S rDNA. The insects harbored a rich diversity of microbes, mainly consisted of bacteria from phyla Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes, and Tenericutes. The composition and abundance of microbiota were more similar as the geographic distance decreased between the populations and clustered by geographic location into three groups: temperate, subtropical, and tropical populations. Although the abundance and species of microbes differed among the populations, the various major microbes for each population performed similar functions based on a clusters of orthologous group analysis. Greater diversity in ecological factors in different regions might lead to higher microbial diversity, thus enabling L. striatellus to adapt or tolerate various extreme environments to avoid the cost of long-distance migration. Moreover, the abundance of various metabolic functions in the Kaifeng populations might contribute to higher fecundity in L. striatellus.

Determination of Suitable RT-qPCR Reference Genes for Studies of Gene Functions in Laodelphax striatellus (Fallén)

The reverse transcription quantitative polymerase chain reaction (RT-qPCR) has been widely used to determine gene functions in Laodelphax striatellus (Fallén) (small brown planthopper). Selection of suitable reference gene(s) for normalizations of RT-qPCR data is critical for reliable results. To date, reports on identification of suitable L. striatellus reference genes are still very limited. L. striatellus is a destructive rice pest and it can transmit multiple viruses, including Rice black-streaked dwarf virus (RBSDV), Rice stripe virus (RSV), and Maize rough dwarf virus (MRDV), to many important cereal crops worldwide. In this study, we examined the stablity of seven selected candidate reference genes in L. striatellus at different developmental stages, in different tissues, in RBSDV- or RSV-infected L. striatellus or in RBSDV-infected and Lssynaptojanin 1 (LsSYNJ1)-silenced L. striatellus. The RT-qPCR data representing individual candidate genes were analyzed using five different methods: the delta Ct method, geNorm, NormFinder, BestKeeper, and the RefFinder algorithm, respectively. The most stable reference gene for the specific condition was selected according to a comprehensive analysis using the RefFinder method. Ribosomal protein L5 (LsRPL5) and LsRPL8 are the most stably expressed genes in L. striatellus at different developmental stages. Alpha-1-tubulin (Lsα-TUB) is the most stably expressed reference gene in different tissues of RBSDV viruliferous (RBSDV-V) or non-viruliferous (RBSDV-NV) L. striatellus. LsRPL8 is the most stably expressed reference gene in RBSDV-V or RSV viruliferous (RSV-V) L. striatellus, while beta-tubulin (Lsβ-TUB) is the most stably expressed reference gene in RBSDV-V and LsSYNJ1-silenced L. striatellus. The selected reference genes were further investigated during analyses of RBSDV P5-1 and P10 gene expression in different tissues from RBSDV-V or RBSDV-NV L. striatellus. The stably expressed reference genes identified in this study will benefit future gene function studies using L. striatellus.

Comparative proteomic analysis of sex-biased proteins in ovary and testis at different stages of Spodoptera litura

Sex-biased protein is thought to be able to drive the phenotypic differences in males and females in insects. In this study, 1385 and 1727 proteins were identified as differentially accumulated proteins (DAPs) by comparing the protein abundances at pupae stage with those at adult stage in ovary and testis of S.litura, respectively. And among which, 548 DAPs were showed to be expressed in both ovary and testis, and 837 and 1179 proteins were considered as ovary-specific and testis-specific DAPs, respectively. To further identify DAPs related to gonad development and sex dimorphism, a total of 320 DAPs were selected and defined as "proteins of specific interest" based on several selecting criteria. Sex dimorphism is a complex and dynamic developmental progress, and these identified DAPs were suggested to be involved in multiple functions such as organonitrogen compound catabolic process, glycosylation, proteasome, N-Glycan biosynthesis and other reproduction-related processes. Overall, our results highlighted these sexual-biased, gonad development related and sexual dimorphism related DAPs, and their abundance variations along with development were also examined, which could provide important information for their functional analysis in reproduction and potential biomarkers for developing useful strategies against S. litura and other orthologous pests. BIOLOGICAL SIGNIFICANCE: Sex dimorphism entails the differentiation of two sexual functions, resulting in sexually phenotypic differences and leading to the development of female and male morphologies and behaviors. However, sex dimorphism related proteins remain to be identified in many non-model insects. In this study, iTRAQ-based proteomic analysis was applied to examine the variations of protein abundances at pupae stage and adult stage in ovary and testis of S.litura, respectively. Reproduction and sex dimorphism related proteins were further identified as "proteins of specific interest". These identified candidate proteins provided valuable information for their further functional analysis in reproduction and could serve as potential biomarkers for developing useful strategies against S. litura and other orthologous pests.

Transcript-Level Analysis of Detoxification Gene Mutation-Mediated Chlorpyrifos Resistance in Laodelphax striatellus (Hemiptera: Delphacidae)

Enhanced detoxification and target mutations that weaken insecticide binding ability are major mechanisms of insecticide resistance. Among these, over-expression or site mutations of carboxylesterase (CarE), cytochrome P450s (CYP450), and glutathione-S-transferase (GST) were the main form responsible for insecticide detoxification; however, transcript-level analysis of the relationship of detoxification gene mutations with chlorpyrifos (an organophosphorus insecticide) resistance is scarce thus far. In this study, multiple sites exhibiting polymorphisms within three detoxification genes were firstly examined via sequencing among different chlorpyrifos-resistant and susceptible individuals of Laodelphax striatellus. For example, the mutation frequencies of A374V in LsCarE16 were 83, 33, and 3%, S277A in LsCarE24 were 88, 28, and 3%, E36K in LsCYP426A1 were 100, 65, and 0% for chlorpyrifos-resistant, resistant decay, and susceptible individuals, respectively. Analysis also found expression levels of GSTd1, GSTt1, GSTs2, CYP4DE1U1, and CYP425B1 are coordinated with chlorpyrifos resistance levels; moreover, we found the deficiencies of 43S and 44A as well as two point mutations of E60D and Q61H at N-terminal region of the OP potential target acetylcholinesterase (AChE) in high resistant but not in low-chlorpyrifos resistant individuals. The results above all demonstrated the dynamic evolutionary process of insecticide resistance and revealed some resistance factors that only played roles at certain resistance level; high insecticide resistance in this example is the result of synergistic impact from multiple resistance factors.

Proteomic analysis reveals large amounts of decomposition enzymes and major metabolic pathways involved in algicidal process of Trametes versicolor F21a

A recent algicidal mode indicates that fungal mycelia can wrap and eliminate almost all co-cultivated algal cells within a short time span. However, the underlying molecular mechanism is rarely understood. We applied proteomic analysis to investigate the algicidal process of Trametes versicolor F21a and identified 3,754 fungal proteins. Of these, 30 fungal enzymes with endo- or exoglycosidase activities such as β-1,3-glucanase, α-galactosidase, α-glucosidase, alginate lyase and chondroitin lyase were significantly up-regulated. These proteins belong to Glycoside Hydrolases, Auxiliary Activities, Carbohydrate Esterases and Polysaccharide Lyases, suggesting that these enzymes may degrade lipopolysaccharides, peptidoglycans and alginic acid of algal cells. Additionally, peptidase, exonuclease, manganese peroxidase and cytochrome c peroxidase, which decompose proteins and DNA or convert other small molecules of algal cells, could be other major decomposition enzymes. Gene Ontology and KEGG pathway enrichment analysis demonstrated that pyruvate metabolism and tricarboxylic acid cycle pathways play a critical role in response to adverse environment via increasing energy production to synthesize lytic enzymes or uptake molecules. Carbon metabolism, selenocompound metabolism, sulfur assimilation and metabolism, as well as several amino acid biosynthesis pathways could play vital roles in the synthesis of nutrients required by fungal mycelia.

Proteomic and Carbonylation Profile Analysis at the Critical Node of Seed Ageing in Oryza sativa

The critical node (CN), which is the transition from the plateau phase to the rapid decreasing phase of seed ageing, is extremely important for seed conservation. Although numerous studies have investigated the oxidative stress during seed ageing, information on the changes in protein abundance at the CN is limited. In this study, we aimed to investigate the abundance and carbonylation patterns of proteins at the CN of seed ageing in rice. The results showed that the germination rate of seeds decreased by less than 20% at the CN; however, the abundance of 112 proteins and the carbonylation levels of 68 proteins markedly changed, indicating oxidative damage. The abundance and activity of mitochondrial, glycolytic, and pentose phosphate pathway proteins were reduced; consequently, this negatively affected energy production and germination. Proteins related to defense, including antioxidant system and heat shock proteins, also reduced in abundance. Overall, energy metabolism was reduced at the CN, leading to a decrease in the antioxidant capacity, whereas seed storage proteins were up-regulated and carbonylated, indicating that the seed had a lower ability to utilize seed storage proteins for germination. Thus, the significant decrease in metabolic activities at the CN might accelerate the loss of seed viability.

Proteomic profile of the Bradysia odoriphaga in response to the microbial secondary metabolite benzothiazole

Benzothiazole, a microbial secondary metabolite, has been demonstrated to possess fumigant activity against Sclerotinia sclerotiorum, Ditylenchus destructor and Bradysia odoriphaga. However, to facilitate the development of novel microbial pesticides, the mode of action of benzothiazole needs to be elucidated. Here, we employed iTRAQ-based quantitative proteomics analysis to investigate the effects of benzothiazole on the proteomic expression of B. odoriphaga. In response to benzothiazole, 92 of 863 identified proteins in B. odoriphaga exhibited altered levels of expression, among which 14 proteins were related to the action mechanism of benzothiazole, 11 proteins were involved in stress responses, and 67 proteins were associated with the adaptation of B. odoriphaga to benzothiazole. Further bioinformatics analysis indicated that the reduction in energy metabolism, inhibition of the detoxification process and interference with DNA and RNA synthesis were potentially associated with the mode of action of benzothiazole. The myosin heavy chain, succinyl-CoA synthetase and Ca⁺-transporting ATPase proteins may be related to the stress response. Increased expression of proteins involved in carbohydrate metabolism, energy production and conversion pathways was responsible for the adaptive response of B. odoriphaga. The results of this study provide novel insight into the molecular mechanisms of benzothiazole at a large-scale translation level and will facilitate the elucidation of the mechanism of action of benzothiazole.

Dynamic Phosphoproteome Analysis of Seedling Leaves in Brachypodium distachyon L. Reveals Central Phosphorylated Proteins Involved in the Drought Stress Response

Drought stress is a major abiotic stress affecting plant growth and development. In this study, we performed the first dynamic phosphoproteome analysis of Brachypodium distachyon L. seedling leaves under drought stress for different times. A total of 4924 phosphopeptides, contained 6362 phosphosites belonging to 2748 phosphoproteins. Rigorous standards were imposed to screen 484 phosphorylation sites, representing 442 unique phosphoproteins. Comparative analyses revealed significant changes in phosphorylation levels at 0, 6, and 24 h under drought stress. The most phosphorylated proteins and the highest phosphorylation level occurred at 6 h. Venn analysis showed that the up-regulated phosphopeptides at 6 h were almost two-fold those at 24 h. Motif-X analysis identified the six motifs: [sP], [Rxxs], [LxRxxs], [sxD], [sF], and [TP], among which [LxRxxs] was also previously identified in B. distachyon. Results from molecular function and protein-protein interaction analyses suggested that phosphoproteins mainly participate in signal transduction, gene expression, drought response and defense, photosynthesis and energy metabolism, and material transmembrane transport. These phosphoproteins, which showed significant changes in phosphorylation levels, play important roles in signal transduction and material transmembrane transport in response to drought conditions. Our results provide new insights into the molecular mechanism of this plant’s abiotic stress response through phosphorylation modification.

Analysis of Sogatella furcifera proteome that interact with P10 protein of Southern rice black-streaked dwarf virus

Southern rice black-streaked dwarf virus (SRBSDV) is transmitted efficiently only by white-backed planthopper (WBPH, Sogatella furcifera) in a persistent propagative manner. Here we used a yeast two-hybrid system to investigate the interactions between the SRBSDV- P10 and the cDNA library of WBPH. Of 130 proteins identified as putative interactors, 28 were further tested in a retransformation analysis and β-galactosidase assay to confirm the interaction. The full-length gene sequences of 5 candidate proteins: vesicle-associated membrane protein 7 (VAMP7), vesicle transport V-SNARE protein (Vti1A), growth hormone-inducible transmembrane protein (Ghitm), nascent polypeptide-associated complex subunit alpha, and ATP synthase lipid-binding protein) were amplified by 5' rapid amplification of cDNA ends (RACE) and used in a GST fusion protein pull-down assay. Three of these proteins interacted with SRBSDV-P10 in vitro experiment GST pull-down assay. In a gene expression analysis of 3 different growth stages and 6 different tissue organs of S. furcifera, the mRNA level of VAMP7 was high in adult males and gut. Vti1A was abundant in adult female, and malpighian tubule, gut and ovary. Ghitm was predominantly found in adult male and the malpighian tubule. These research findings are greatly helpful to understand the interaction between SRBSDV and insect vector.