Proteomic analysis of responsive stem proteins of resistant and susceptible cashew plants after Lasiodiplodia theobromae infection

The woody plant-degrading pathogen Lasiodiplodia theobromae effector LtCre1 targets the grapevine sugar-signaling protein VvRHIP1 to suppress host immunity

Lasiodiplodia theobromae is a causal agent of Botryosphaeria dieback, which seriously threatens grapevine production worldwide. Plant pathogens secrete diverse effectors to suppress host immune responses and promote the progression of infection, but the mechanisms underlying the manipulation of host immunity by L. theobromae effectors are poorly understood. In this study, we characterized LtCre1, which encodes a L. theobromae effector that suppresses BAX-triggered cell death in Nicotiana benthamiana. RNAi-silencing and overexpression of LtCre1 in L. theobromae showed impaired and increased virulence, respectively, and ectopic expression in N. benthamiana increased susceptibility. These results suggest that LtCre1 is as an essential virulence factor for L. theobromae. Protein-protein interaction studies revealed that LtCre1 interacts with grapevine RGS1-HXK1-interacting protein 1 (VvRHIP1). Ectopic overexpression of VvRHIP1 in N. benthamiana reduced infection, suggesting that VvRHIP1 enhances plant immunity against L. theobromae. LtCre1 was found to disrupt the formation of the VvRHIP1-VvRGS1 complex and to participate in regulating the plant sugar-signaling pathway. Thus, our results suggest that L. theobromae LtCre1 targets the grapevine VvRHIP1 protein to manipulate the sugar-signaling pathway by disrupting the association of the VvRHIP1-VvRGS1 complex.

The bZIP Transcription Factor LtAP1 Modulates Oxidative Stress Tolerance and Virulence in the Peach Gummosis Fungus Lasiodiplodia theobromae

Lasiodiplodia theobromae is one of the primary causal agents in peach gummosis disease, leading to enormous losses in peach production. In our previous study, a redox-related gene, LtAP1, from the fungus was significantly upregulated in peach shoots throughout infection. Here, we characterized LtAP1, a basic leucine zipper transcription factor, during peach gummosis progression using the CRISPR-Cas9 system and homologous recombination. The results showed that LtAP1-deletion mutant had slower vegetative growth and increased sensitivity to several oxidative and nitrosative stress agents. LtAP1 was highly induced by exogenous oxidants treatment in the L. theobromae wild-type strain. In a pathogenicity test, the deletion mutant showed decreased virulence (reduced size of necrotic lesions, less gum release, and decreased pathogen biomass) on infected peach shoots compared to the wild-type strain. The mutant showed severely reduced transcription levels of genes related to glutaredoxin and thioredoxin in L. theobroame under oxidative stress or during infection, indicating an attenuated capacity for reactive oxygen species (ROS) detoxification. When shoots were treated with an NADPH oxidase inhibitor, the pathogenicity of the mutant was partially restored. Moreover, ROS production and plant defense response were strongly activated in peach shoots infected by the mutant. These results highlight the crucial role of LtAP1 in the oxidative stress response, and further that it acts as an important virulence factor through modulating the fungal ROS-detoxification system and the plant defense response.

Extraction and identification of biologically important proteins from the medicinal plant God's crown (Phaleria macrocarpa)

The fruit and leaf of God's crown (Phaleria macrocarpa) have been traditionally used to treat a wide variety of diseases. However, the proteins of this tropical plant are still heavily understudied. Three protein extraction methods; phenol (Phe), trichloroacetic acid (TCA)-acetone-phenol (TCA-A-Phe), and ultrasonic (Ult) were compared on the fruit and leaf of P. macrocarpa. The Phe extraction method showed the highest percentage of recovered protein after the resolubilization process for both leaf (12.24%) and fruit (30.41%) based on protein yields of the leaf (6.15 mg/g) and fruit (36.98 mg/g). Phe and TCA-A-Phe extraction methods gave well-resolved bands over a wide range of molecular weights through sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Following liquid chromatography-tandem mass spectrometry analysis, proteins identified through the Phe extraction method were 30%-35% enzymatic proteins, including oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases that possess various biological functions. PRACTICAL APPLICATIONS: Every part of God's crown plant is traditionally consumed to treat various illnesses. While plant's benefits are well known and have led to a plethora of health products, the proteome remains mostly unknown. This study compares three protein extraction methods for the leaf and fruit of P. macrocarpa and identifies their proteins thru LC-MS/MS coupled with PEAKS. These method comparisons can be a guide for works on other plants as well. In addition, the proteomics data from this study may shed light on the functional properties of these plant parts and their products.

ApSerpin-ZX from Agapanthus praecox, is a potential cryoprotective agent to plant cryopreservation

Cryopreservation-induced cell death is regarded as an important problem faced by cryobiologists. Oxidative stress and programmed cell death are detrimental to cell survival. Serine protease inhibitors (serpins) inhibit pro-cell-death proteases and play a pro-survival role in excessive cell death induced by abiotic stress. In this study, ApSerpin-ZX was isolated from Agapanthus praecox and characterized as a protective protein in plant cryopreservation. The mRNA level of ApSerpin-ZX was elevated under abiotic stress, such as salt, osmosis, oxidative, cold, and cryoinjury. The purified recombinant protein expressed in E. coli was added to the plant vitrification solution and used for A. praecox embryogenic callus cryopreservation. The concentration of 0.6-4.8 mg∙L^-1 of ApSerpin-ZX protein was beneficial to the survival of cryopreserved embryogenic callus of A. praecox. The most effective concentration was 1.2 mg∙L^-1, which elevated the survival by 37.15%. Subsequently, the cryopreservation procedure with 1.2 mg∙L^-1 of ApSerpin-ZX protein was regarded as the treated group, compared to standard procedure, to determine the physiological mechanism of ApSerpin-ZX protein on cryopreserved cell. The MDA and H₂O₂ contents were significantly decreased in the treated group, along with reduced OH· generation activity in the recovery stage. After the addition of ApSerpin-ZX, the POD and CAT activities keep increased, while SOD activity increased only after dehydration. Besides, the caspase-1-like and caspase-3-like activities were lower than the standard procedure. This study indicated that ApSerpin-ZX was a potential cryoprotective agent that alleviated oxidative stress and cell death induced by cryopreservation.

The pathogen Moniliophthora perniciosa promotes differential proteomic modulation of cacao genotypes with contrasting resistance to witches´ broom disease

BACKGROUND

Witches' broom disease (WBD) of cacao (Theobroma cacao L.), caused by Moniliophthora perniciosa, is the most important limiting factor for the cacao production in Brazil. Hence, the development of cacao genotypes with durable resistance is the key challenge for control the disease. Proteomic methods are often used to study the interactions between hosts and pathogens, therefore helping classical plant breeding projects on the development of resistant genotypes. The present study compared the proteomic alterations between two cacao genotypes standard for WBD resistance and susceptibility, in response to M. perniciosa infection at 72 h and 45 days post-inoculation; respectively the very early stages of the biotrophic and necrotrophic stages of the cacao x M. perniciosa interaction.

RESULTS

A total of 554 proteins were identified, being 246 in the susceptible Catongo and 308 in the resistant TSH1188 genotypes. The identified proteins were involved mainly in metabolism, energy, defense and oxidative stress. The resistant genotype showed more expressed proteins with more variability associated with stress and defense, while the susceptible genotype exhibited more repressed proteins. Among these proteins, stand out pathogenesis related proteins (PRs), oxidative stress regulation related proteins, and trypsin inhibitors. Interaction networks were predicted, and a complex protein-protein interaction was observed. Some proteins showed a high number of interactions, suggesting that those proteins may function as cross-talkers between these biological functions.

CONCLUSIONS

We present the first study reporting the proteomic alterations of resistant and susceptible genotypes in the T. cacao x M. perniciosa pathosystem. The important altered proteins identified in the present study are related to key biologic functions in resistance, such as oxidative stress, especially in the resistant genotype TSH1188, that showed a strong mechanism of detoxification. Also, the positive regulation of defense and stress proteins were more evident in this genotype. Proteins with significant roles against fungal plant pathogens, such as chitinases, trypsin inhibitors and PR 5 were also identified, and they may be good resistance markers. Finally, important biological functions, such as stress and defense, photosynthesis, oxidative stress and carbohydrate metabolism were differentially impacted with M. perniciosa infection in each genotype.

Comparative proteomics of two citrus varieties in response to infection by the fungus Alternaria alternata

Alternaria brown spot (ABS) is a disease caused by the necrotrophic fungus Alternaria alternata, which induces necrotic lesions on fruits and young leaves due to the production of the host-specific ACT toxin by the fungus. To better understand the citrus-A. alternata interaction and to identify putative resistance proteins, as well as the receptor of the ACT toxin, citrus plants susceptible ('Minneola' mandarin) and resistant ('Clemenules' tangor) to A. alternata, infected or not (control) with the pathogen were analyzed by proteomics. Protein changes were observed between citrus genotypes after infection, and 150 candidate proteins were obtained. A general scheme of the metabolic processes involved in susceptible and resistant citrus-A. alternata interactions was designed. Susceptible plants presented a high level of proteins involved in stress response at the final stages of the infection, whereas resistant plants presented high level of ROS proteins, metabolic proteins, and proteins involved in the immune system process. Proteins like ferredoxin and cyclophilin are specific to the susceptible variety and may be good candidates as fungal effector-interacting proteins. This is the first citrus-A. alternata proteomics analysis, which has allowed a better understanding of the molecular bases of the citrus response to ABS disease.

Proteomic Analysis Reveals the Positive Roles of the Plant-Growth-Promoting Rhizobacterium NSY50 in the Response of Cucumber Roots to Fusarium oxysporum f. sp. cucumerinum Inoculation

Plant-growth-promoting rhizobacteria (PGPR) can both improve plant growth and enhance plant resistance against a variety of environmental stresses. To investigate the mechanisms that PGPR use to protect plants under pathogenic attack, transmission electron microscopy analysis and a proteomic approach were designed to test the effects of the new potential PGPR strain Paenibacillus polymyxa NSY50 on cucumber seedling roots after they were inoculated with the destructive phytopathogen Fusarium oxysporum f. sp. cucumerinum (FOC). NSY50 could apparently mitigate the injury caused by the FOC infection and maintain the stability of cell structures. The two-dimensional electrophoresis (2-DE) approach in conjunction with MALDI-TOF/TOF analysis revealed a total of 56 proteins that were differentially expressed in response to NSY50 and/or FOC. The application of NSY50 up-regulated most of the identified proteins that were involved in carbohydrate metabolism and amino acid metabolism under normal conditions, which implied that both energy generation and the production of amino acids were enhanced, thereby ensuring an adequate supply of amino acids for the synthesis of new proteins in cucumber seedlings to promote plant growth. Inoculation with FOC inhibited most of the proteins related to carbohydrate and energy metabolism and to protein metabolism. The combined inoculation treatment (NSY50+FOC) accumulated abundant proteins involved in defense mechanisms against oxidation and detoxification as well as carbohydrate metabolism, which might play important roles in preventing pathogens from attacking. Meanwhile, western blotting was used to analyze the accumulation of enolase (ENO) and S-adenosylmethionine synthase (SAMs). NSY50 further increased the expression of ENO and SAMs under FOC stress. In addition, NSY50 adjusted the transcription levels of genes related to those proteins. Taken together, these results suggest that P. polymyxa NSY50 may promote plant growth and alleviate FOC-induced damage by improving the metabolism and activation of defense-related proteins in cucumber roots.

Comparative proteomic analysis provides novel insight into the interaction between resistant vs susceptible tomato cultivars and TYLCV infection

BACKGROUND

Tomato yellow leaf curl virus (TYLCV) is a member of the family Geminiviridae, genus Begomovirus. The virus is a widespread plant virus that causes important economic losses in tomatoes. Genetic engineering strategies have increasingly been adopted to improve the resistance of tomatoes to TYLCV.

RESULTS

In this study, a proteomic approach was used to investigate the molecular mechanisms involved in tomato leaf defense against TYLCV infection. Proteins extracted from leaves of resistant tomato cultivar 'Zheza-301' and susceptible cultivar 'Jinpeng-1' after TYLCV infection were analyzed using two-dimensional gel electrophoresis. Eighty-six differentially expressed proteins were identified and classified into seven groups based on their functions. For several of the proteins, including CDC48, CHI and HSC70, expression patterns measured using quantitative real-time PCR differed from the results of the proteomic analysis. A putative interaction network between tomato leaves and TYLCV infection provides us with important information about the cellular activities that are involved in the response to TYLCV infection.

CONCLUSIONS

We conducted a comparative proteomic study of TYLCV infection in resistant and susceptible tomato cultivars. The proteins identified in our work show a variety of functions and expression patterns in the process of tomato-TYLCV interaction, and these results contribute to our understanding of the mechanism underlying TYLCV resistance in tomatoes at the protein level.