Expression Of Pathogenesis-related Proteins Research Articles

The key pathogenic factor GcSP2 of Geotrichum citri-aurantii plays an important role in disrupting citrus metabolism and immunity

The pathogen Geotrichum citri-aurantii (G. citri-aurantii) causes postharvest sour rot disease in citrus fruits worldwide, severely impacting citrus economic value. However, the pathogenic mechanisms of this fungus remain inadequately understood. Here, we identified 15 candidate effector proteins from G. citri-aurantii genome, of which five were highly expressed during infection and were capable of suppressing BAX-induced cell death, indicating their role in inhibiting plant immunity. Gene expression analysis showed that these five effector proteins primarily induced the upregulation of pattern-triggered immunity (PTI)-related gene expression. Diaminobenzidine (DAB) staining results indicated that only GcSP2 triggered reactive oxygen species (ROS) burst. Notably, GcSP2 contains a known carbohydrate-binding module 1 (CBM1) domain and exhibits low overall conservation. Gene knockout experiments revealed that the absence of GcSP2 delayed disease onset by 1–2 days and significantly reduced lesion size, establishing it as a key pathogenic factor. Assessments of total phenols, flavonoids, and pathogenesis-related protein expression indicated that GcSP2 significantly affects citrus metabolism at 72 hours post-infection.

Dissecting the role of salicylic acid in mediating stress response in mungbean cultivars concurrently exposed to Macrophomina phaseolina infection and drought stress

The combined stress studies provide fundamental knowledge that could assist in producing multiple stress resilient crops. The fungal phytopathogen, Macrophomina phaseolina is a major limiting factor in the productivity of the crop, Vigna radiata (mungbean). This fungal species tends to flourish under hot and dry conditions. Therefore, in this study the salicylic acid (SA) mediated stress responses in contrasting mungbean cultivars (Shikha and RMG-975) exposed to combined M. phaseolina infection (F) and drought stress (D) have been elucidated. The combined stress was applied to ten days seedlings in three orders i.e. drought followed by fungal infection (DF), drought followed by fungal infection with extended water deficit (DFD) and fungal infection followed by drought stress (FD). The severity of infection was analyzed using ImageJ analysis. Besides, the concentration of SA has been correlated with the phenylpropanoid pathway products, expression of pathogenesis-related proteins (β-1,3-glucanase and chitinase) and the specific activity of certain related enzymes (phenylalanine ammonia lyase, lipoxygenase and glutathione-S-transferase). The data revealed that the cultivar RMG-975 was relatively more tolerant than Shikha under individual stresses. However, the former became more susceptible to the infection under DFD treatment while the latter showed tolerance. Otherwise, the crown rot severity was reduced in both the cultivars under other combined treatments. The stress response analysis suggested that enhanced chitinase expression is vital for tolerance against both, the pathogen and drought stress. Also, it was noted that plants treat each stress combination differently and the role of SA was more prominently visible under individual stress conditions.

Characterization of soybean chitinase genes induced by rhizobacteria involved in the defense against Fusarium oxysporum.

Rhizobacteria are capable of inducing defense responses via the expression of pathogenesis-related proteins (PR-proteins) such as chitinases, and many studies have validated the functions of plant chitinases in defense responses. Soybean (Glycine max) is an economically important crop worldwide, but the functional validation of soybean chitinase in defense responses remains limited. In this study, genome-wide characterization of soybean chitinases was conducted, and the defense contribution of three chitinases (GmChi01, GmChi02, or GmChi16) was validated in Arabidopsis transgenic lines against the soil-borne pathogen Fusarium oxysporum. Compared to the Arabidopsis Col-0 and empty vector controls, the transgenic lines with GmChi02 or GmChi16 exhibited fewer chlorosis symptoms and wilting. While GmChi02 and GmChi16 enhanced defense to F. oxysporum, GmChi02 was the only one significantly induced by Burkholderia ambifaria. The observation indicated that plant chitinases may be induced by different rhizobacteria for defense responses. The survey of 37 soybean chitinase gene expressions in response to six rhizobacteria observed diverse inducibility, where only 10 genes were significantly upregulated by at least one rhizobacterium and 9 genes did not respond to any of the rhizobacteria. Motif analysis on soybean promoters further identified not only consensus but also rhizobacterium-specific transcription factor-binding sites for the inducible chitinase genes. Collectively, these results confirmed the involvement of GmChi02 and GmChi16 in defense enhancement and highlighted the diverse inducibility of 37 soybean chitinases encountering F. oxysporum and six rhizobacteria.

Studies on biochemical changes and expression of Pathogenesis-Related proteins (PR Proteins) associated with plant defense mechanism induced by Arbuscular Mycorhizal Fungus Rhizophagus intraradices against Meloidogyne incognita

Studies on biochemical changes and expression of Pathogenesis-Related proteins (PR Proteins) associated with plant defense mechanism induced by Arbuscular Mycorhizal Fungus Rhizophagus intraradices against Meloidogyne incognita

EXPRESSION OF CHITINASE AND -1,3-GLUCANASES IN RICE CULTIVARS IN REACTION TO Rhizoctonia solani,THE CAUSAL AGENT OF RICE SHEATH BLIGHT

Fifteen high yielding rice cultivars were screened for their reaction to sheath blight under field as well as semi-controlled conditions inoculated with the pathogen Rhizoctonia solani Kuhn. Expression of two pathogenesis related proteins (PRPs), Chitinase and -1,3-glucanases activities were estimated. Both chitinase and 1,3-glucanase PR proteins activity in terms of specific activity expressed after 72 h of pathogen inoculation was generally higher in tolerant cultivars (NLR 145, MTU 1061, NLR 3238, MTU 1153) including checks (TETEP and MTU 1001) as compared to control (MTU 7029) and other susceptible cultivars. The presence of a 33 kDachitinase and 32 kDa and -1,3-glucanase proteins was revealed by western blot analysis, across all the rice cultivars following Rhizoctonia solani infection. No significant grain yield difference in relation to the expression of PRPs was observed across the test rice cultivars.

Spraying chitosan on cassava roots reduces postharvest deterioration by promoting wound healing and inducing disease resistance

Postharvest damage makes cassava roots vulnerable to pathogen infections and decay, which significantly hinders the development of the cassava industry. The objective of this study was to assess the antibacterial properties of chitosan in vitro, as well as its effect on wound healing and resistance in cassava roots. The findings demonstrated that the bacteriostatic effect of chitosan became increasingly prominent as the concentration of chitosan enhanced. Chitosan at a concentration of 0.5 mg/mL was revealed to significantly inhibit the germination of P. palmivora spores and damage to their structure. Moreover, chitosan activated the transcription of crucial genes and enzyme activities associated with the phenylpropane metabolism pathway in cassava roots, thus promoting rapid lignin accumulation and resulting in the early formation of a fracture layer. Chitosan was also found to enhance cassava root resistance by promoting the expression of pathogenesis-related proteins and the accumulation of flavonoids and total phenols. After 48 h of inoculation, cassava roots treated with chitosan exhibited a 51.4 % and 53.4 % decrease in lesion area for SC9 and SC6 varieties, respectively. The findings of this study offer a novel approach for managing postharvest deterioration of cassava roots.

Differences in Pathogenesis-Related Protein Expression and Polyphenolic Compound Accumulation Reveal Insights into Tomato–Pythium aphanidermatum Interaction

Plant diseases significantly reduce crop yields, threatening food security and agricultural sustainability. Fungi are the most destructive type of phytopathogen, and they are responsible for major yield losses in some of the most crucial crops grown across the world. In this study, a fungus isolate was detected from infected tomato plants and molecularly identified as Pythium aphanidermatum (GenBank accession number MW725032). This fungus caused damping-off disease and was shown to be pathogenic. Moreover, the expression of five pathogenesis-related genes, namely PR-1, PR-2, PR-3, PR-4, and PR-5, was quantitatively evaluated under the inoculation of tomato with P. aphanidermatum. The quantitative polymerase chain reaction (qPCR) showed that the expression levels of PR-1, PR-2, and PR-5 genes went up significantly at 5 days post-inoculation (dpi). The expression of the PR-1 gene also increased the variably, which reached its highest value at 20 dpi, with a reported relative expression level 6.34-fold higher than that of the control. At 15 dpi, PR-2 and PR-5 increased the most, while PR-1, PR-3, and PR-5 also increased noticeably at 20 dpi. On the contrary, PR-4 gene expression significantly decreased after inoculation, at all time intervals. Regarding PR-5 gene expression, the data showed a variable change in PR-5 gene expression at a different sample collection period. Still, it was highly expressed at 15 dpi and reached 3.99-fold, followed by 20 dpi, where the increasing percentage reached 3.70-fold, relative to the untreated control. The HPLC analysis indicated that the total concentration of all detected polyphenolic compounds was 3858 µg/g and 3202.2 µg/g in control and infected plant leaves, respectively. Moreover, the HPLC results concluded that Pythium infection decreased phenolic acids, such as chlorogenic and ellagic acids, which correlated with the infection–plant complex process. Based on the results, P. aphanidermatum could be a biotic stress pathogen that causes the expression of pathogen-related genes and stops the regulation of defensin phenolic compounds.

Physiological and molecular insight of microbial biostimulants for sustainable agriculture.

Increased food production to cater the need of growing population is one of the major global challenges. Currently, agro-productivity is under threat due to shrinking arable land, increased anthropogenic activities and changes in the climate leading to frequent flash floods, prolonged droughts and sudden fluctuation of temperature. Further, warm climatic conditions increase disease and pest incidences, ultimately reducing crop yield. Hence, collaborated global efforts are required to adopt environmentally safe and sustainable agro practices to boost crop growth and productivity. Biostimulants appear as a promising means to improve growth of plants even under stressful conditions. Among various categories of biostimulants, microbial biostimulants are composed of microorganisms such as plant growth-promoting rhizobacteria (PGPR) and/or microbes which stimulate nutrient uptake, produce secondary metabolites, siderophores, hormones and organic acids, participate in nitrogen fixation, imparts stress tolerance, enhance crop quality and yield when applied to the plants. Though numerous studies convincingly elucidate the positive effects of PGPR-based biostimulants on plants, yet information is meagre regarding the mechanism of action and the key signaling pathways (plant hormone modulations, expression of pathogenesis-related proteins, antioxidants, osmolytes etc.) triggered by these biostimulants in plants. Hence, the present review focuses on the molecular pathways activated by PGPR based biostimulants in plants facing abiotic and biotic challenges. The review also analyses the common mechanisms modulated by these biostimulants in plants to combat abiotic and biotic stresses. Further, the review highlights the traits that have been modified through transgenic approach leading to physiological responses akin to the application of PGPR in the target plants.

Global analysis of lysine 2-hydroxyisobutyrylation during Fusarium graminearum infection in maize.

Proteins post-translational modification (PTMs) is necessary in the whole life process of organisms. Among them, lysine 2-hydroxyisobutyrylation (Khib) plays an important role in protein synthesis, transcriptional regulation, and cell metabolism. Khib is a newly identified PTM in several plant species. However, the function of Khib in maize was unclear. In this study, western blotting results showed that Khib modification level increased significantly after Fusarium graminearum infection, and 2,066 Khib modified sites on 728 proteins were identified in maize, among which 24 Khib sites occurred on core histones. Subcellular localization results showed that these Khib modified proteins were localized in cytoplasm, chloroplast, and nucleus. Then, comparative proteomic analysis of the defense response to F. graminearum infection showed that Khib modification participated in plant resistance to pathogen infection by regulating glycolysis, TCA cycle, protein synthesis, peroxisome, and secondary metabolic processes, such as benzoxazinoid biosynthesis, phenylpropanoid biosynthesis, jasmonic acid synthesis, and tyrosine and tryptophan biosynthesis. In addition, we also demonstrated that lysine 2-hydroxyisobutyrylation sites on histones were involved in the gene expression of pathogenesis-related proteins. Our results provide a new perspective for the study of plant disease resistance, and had directive significance of maize disease resistance for molecular breeding.

Transcriptomic Analysis of Genes Involved in Plant Defense Response to the Cucumber Green Mottle Mosaic Virus Infection.

Plants have evolved a complex multilayered defense system to counteract various invading pathogens during their life cycle. In addition to silencing, considered to be a major molecular defense response against viruses, different signaling pathways activated by phytohormones trigger the expression of secondary metabolites and proteins preventing virus entry and propagation. In this study, we explored the response of cucumber plants to one of the global pathogens, cucumber green mottle mosaic virus (CGMMV), which causes severe symptoms on leaves and fruits. The inbred line of Cucumis sativus L., which is highly susceptible to CGMMV, was chosen for inoculation. Transcriptomes of infected plants at the early and late stages of infection were analyzed in comparison with the corresponding transcriptomes of healthy plants using RNA-seq. The changes in the signaling pathways of ethylene and salicylic and jasmonic acids, as well as the differences in silencing response and expression of pathogenesis-related proteins and transcription factors, were revealed. The results show that silencing was strongly suppressed in infected plants, while the salicylic acid and ethylene signaling pathways were induced. The genes encoding pathogenesis-related proteins and the genes involved in the jasmonic acid pathway changed their expression insignificantly. It was also found that WRKY and NAC were the most sensitive to CGMMV infection among the transcription factors detected.

Oligosaccharins as Elicitors of Defense Responses in Wheat.

Wheat is a highly relevant crop worldwide, and like other massive crops, it is susceptible to foliar diseases, which can cause devastating losses. The current strategies to counteract wheat diseases include global monitoring of pathogens, developing resistant genetic varieties, and agrochemical applications upon diseases’ appearance. However, the suitability of these strategies is far from permanent, so other alternatives based on the stimulation of the plants’ systemic responses are being explored. Plants’ defense mechanisms can be elicited in response to the perception of molecules mimicking the signals triggered upon the attack of phytopathogens, such as the release of plant and fungal cell wall-derived oligomers, including pectin and chitin derivatives, respectively. Among the most studied cell wall-derived bioelicitors, oligogalacturonides and oligochitosans have received considerable attention in recent years due to their ability to trigger defense responses and enhance the synthesis of antipathogenic compounds in plants. Particularly, in wheat, the application of bioelicitors induces lignification and accumulation of polyphenolic compounds and increases the gene expression of pathogenesis-related proteins, which together reduce the severity of fungal infections. Therefore, exploring the use of cell wall-derived elicitors, known as oligosaccharins, stands as an attractive option for the management of crop diseases by improving plant readiness for responding promptly to potential infections. This review explores the potential of plant- and fungal-derived oligosaccharins as a practical means to be implemented in wheat crops.

Enriched Agriculture Horticulture Science Technology Socio-EconomyCommunication-Issue by Biomedicines Suppressing Tomato-Disease and Coronavirus 2-Like-Pandemic-Diseases!

To avoid traditional control of root-knot disease, there remains a need for developing effective biomedicines of animal origins. The animal biomedicines; Nematode Extract (NE) and Gall Protein (GP) when applied by foliar spray, are highly effective at 1.3mg/plant and 2.01mg/plant, respectively in ameliorating root-knot disease of tomato (Lycopersicon lycopersicum, Cv. Pusa Ruby) caused by Meloidogyne incognita (Kofoid & White) Chitwood, promoting plant growth and fruit production. The nematode extract (NE) is more effective than the gall protein (GP) in this respect. Both the extract is thought to induce systemic acquired resistance response of the treated plants through the expression of pathogenesis-related proteins, and may prevent 21st –century pandemics COVID-19 like virus diseases by boosting immunity, resisting toxic effects on the environment, and improved agriculture green-socio-economy aquatic-science-technology-communication application issues, and it may also give a good scope for new advanced-development and research in the field “Agricultural, Horticulture, Earth-Environmental-Clinical-Toxicology-Health-Research, Science-Technology-Communication-Socio-Economy and May be Controlled 21st-Century Pandemic Diseases in Future New Normal Situation Also”.

Preliminary investigations on the pathogenesis-related protein expression profile of the medicinal herb Macleaya cordata and anti-bacterial properties of recombinant proteins

The plant pathogenesis-related (PR) proteins play a crucial role in the defense of plants against pathogens and orchestrate the innate immune system of plants. In this paper, a non-normalized cDNA library of the leaf was constructed to obtain a comprehensive view of PR proteins of Macleaya cordata. Specifically, 511 expressed sequence tags (ESTs) were generated using Sanger sequencing. All ESTs were assembled into 364 non-redundancy sequences, including 78 clusters and 286 singlets. The PR protein expression profile of the medicinal herb M. cordata has been investigated and is represented by defensin, lipid-transfer protein, (S)-norcoclaurine synthase, and major allergen protein, suggesting that the herb contains rich active proteins against pathogens. Furthermore, two defensins were selected for recombinant expression in yeast, and the antimicrobial activities were explored. Since they both present a broad antimicrobial spectrum, they are of particular importance for agricultural and medicinal applications. Our study describes defensins in Papaveraceae for the first time and provides novel insights into the effective components. In addition to the alkaloids, PR proteins (such as defensins, lipid transfer proteins, (S) - norcoclaurine synthase, major allergen protein, and Class IV chitinases) are involved in the antibacterial and anti-inflammatory activities of M. cordata.

The oligomeric states of elicitins affect the hypersensitive response and resistance in tobacco.

Successful plant defence against microbial pathogens is based on early recognition and fast activation of inducible responses. Key mechanisms include detection of microbe-associated molecular patterns by membrane-localized pattern recognition receptors that induce a basal resistance response. A well-described model of such responses to pathogens involves the interactions between Solanaceae plants and proteinaceous elicitors secreted by oomycetes, called elicitins. It has been hypothesized that the formation of oligomeric structures by elicitins could be involved in their recognition and activation of defensive transduction cascades. In this study, we tested this hypothesis using several approaches, and we observed differences in tobacco plant responses induced by the elicitin β-cryptogein (β-CRY) and its homodimer, β-CRYDIM. We also found that the C-terminal domain of elicitins of other ELI (true-elicitin) clades plays a significant role in stabilization of their oligomeric structure and restraint in the cell wall. In addition, covalently cross-linking β-CRYDIM impaired the formation of signalling complexes, thereby reducing its capacity to elicit the hypersensitive response and resistance in the host plant, with no significant changes in pathogenesis-related protein expression. By revealing the details of the effects of β-CRY dimerization on recognition and defence responses in tobacco, our results shed light on the poorly understood role of elicitins' oligomeric structures in the interactions between oomycetes and plants.

Novel Pathway of Heat Shock- Induced Resistance in Tomato

High-temperature treatment induces disease resistance in various plants (heat shock-induced resistance; HSIR). The role of heat shock transcriptional factors (Hsfs) was investigated in this paper. Heat shock treatment induced disease resistance and up-regulate gene expression of pathogenesis related protein; PR1a2 at 12 and 24 h after treatment. PR1a2 has putative Hsfs binding site in the upstream area. On the other hand, a heat shock transcription factor HsfA2 up-regulated at 6 h after treatment, which was 6 h earlier than salicylic acid accumulation. This time lag suggested the direct contribution of Hsfs, additionally to salicylic acid pathway in the regulation of HSIR in tomato.

Aphid infestation differently affects the defences of nitrate-fed and nitrogen-fixing Medicago truncatula and alters symbiotic nitrogen fixation.

Legumes can meet their nitrogen requirements through root nodule symbiosis, which could also trigger plant systemic resistance against pests. The pea aphid Acyrthosiphon pisum, a legume pest, can harbour different facultative symbionts (FS) influencing various traits of their hosts. It is therefore worth determining if and how the symbionts of the plant and the aphid modulate their interaction. We used different pea aphid lines without FS or with a single one (Hamiltonella defensa, Regiella insecticola, Serratia symbiotica) to infest Medicago truncatula plants inoculated with Sinorhizobium meliloti (symbiotic nitrogen fixation, SNF) or supplemented with nitrate (non-inoculated, NI). The growth of SNF and NI plants was reduced by aphid infestation, while aphid weight (but not survival) was lowered on SNF compared to NI plants. Aphids strongly affected the plant nitrogen fixation depending on their symbiotic status, suggesting indirect relationships between aphid- and plant-associated microbes. Finally, all aphid lines triggered expression of Pathogenesis-Related Protein 1 (PR1) and Proteinase Inhibitor (PI), respective markers for salicylic and jasmonic pathways, in SNF plants, compared to only PR1 in NI plants. We demonstrate that the plant symbiotic status influences plant–aphid interactions while that of the aphid can modulate the amplitude of the plant's defence response.

Phakopsora pachyrhizi triggers the jasmonate signaling pathway during compatible interaction in soybean and GmbZIP89 plays a role of major component in the pathway

The biotrophic fungus Phakopsora pachyrhizi is currently the major pathogen affecting soybean production worldwide. It has already been suggested for the non-host interaction between P. pachyrhizi and Arabidopsis thaliana that the fungus in early infection induces jasmonic acid (JA) pathway to the detriment of the salicylic acid (SA) pathway as a mechanism to the establishment of infection. In this study, we verified that this mechanism might also be occurring during the compatible interaction in soybean (Glycine max L. Merril). It was demonstrated that P. pachyrhizi triggers a JA pathway during the early and late stages of infection in a susceptible soybean cultivar. The expression of the GmbZIP89 was induced in a biphasic profile, similarly to other JA responsive genes, which indicates a new marker gene for this signaling pathway. Additionally, plants silenced for GmbZIP89 (iGmZIP89) by the virus-induced gene silencing (VIGS) approach present lower severity of infection and higher expression of pathogenesis related protein 1 (PR1). The lower disease severity showed that the iGmbZIP89 plants became more resistant to infection. These data corroborate the hypothesis that the GmbZIP89 may be a resistance negative regulator. In conclusion, we demonstrated that P. pachyrhizi mimics a necrotrophic fungus and activates the JA/ET pathway in soybean. It is possible to suppose that its direct penetration on epidermal cells or fungal effectors may modulate the expression of target genes aiming the activation of the JA pathway and inhibition of SA defense.

The Combined Effect of Elevated O3 Levels and TYLCV Infection Increases the Fitness of Bemisia tabaci Mediterranean on Tomato Plants.

Global change and biotic stress, such as tropospheric contamination and virus infection, can individually modify the quality of host plants, thereby altering the palatability of the plant for herbivorous insects. The bottom-up effects of elevated O3 and tomato yellow leaf curl virus (TYLCV) infection on tomato plants and the associated performance of Bemisia tabaci Mediterranean (MED) were determined in open-top chambers. Elevated O3 decreased eight amino acid levels and increased the salicylic acid (SA) and jasmonic acid (JA) content and the gene expression of pathogenesis-related protein (PR1) and proteinase inhibitor (PI1) in both wild-type (CM) and JA defense-deficient tomato genotype (spr2). TYLCV infection and the combination of elevated O3 and TYLCV infection increased eight amino acids levels, SA content and PR1 expression, and decreased JA content and PI1 expression in both tomato genotypes. In uninfected tomato, elevated O3 increased developmental time and decreased fecundity by 6.1 and 18.8% in the CM, respectively, and by 6.8 and 18.9% in the spr2, respectively. In TYLCV-infected tomato, elevated O3 decreased developmental time and increased fecundity by 4.6 and 14.2%, respectively, in the CM and by 4.3 and 16.8%, respectively, in the spr2. These results showed that the interactive effects of elevated O3 and TYLCV infection partially increased the amino acid content and weakened the JA-dependent defense, resulting in increased population fitness of MED on tomato plants. This study suggests that whiteflies would be more successful at TYLCV-infected plants than at uninfected plants in elevated O3 levels.

Mildew Resistance Locus O Genes CsMLO1 and CsMLO2 Are Negative Modulators of the Cucumis sativus Defense Response to Corynespora cassiicola.

Corynespora leaf spot caused by Corynespora cassiicola is one of the major diseases in cucumber (Cucumis sativus L.). However, the resistance mechanisms and signals of cucumber to C. cassiicola are unclear. Here, we report that the mildew resistance locus O (MLO) genes, CsMLO1 and CsMLO2, are both negative modulators of the cucumber defense response to C. cassiicola. Subcellular localization analysis showed that CsMLO1 and CsMLO2 are localized in the plasma membrane. Expression analysis indicated that the transcript levels of CsMLO1 and CsMLO2 are linked to the defense response to C. cassiicola. Transient overexpression of either CsMLO1 or CsMLO2 in cucumber cotyledons reduced resistance to C. cassiicola, whereas silencing of either CsMLO1 or CsMLO2 enhanced resistance to C. cassiicola. The relationships of pathogenesis-related proteins, reactive oxygen species (ROS)-associated genes, and abscisic acid (ABA)-related genes to the overexpression and silencing of CsMLO1/CsMLO2 in non-infested cucumber plants were investigated. The results indicated that CsMLO1 mediated resistance against C. cassiicola by regulating the expression of pathogenesis-related proteins and ROS-associated genes, as well as through ABA signaling pathway-associated genes. The CsMLO2-mediated resistance against C. cassiicola primarily involves regulation of the expression of pathogenesis-related proteins. Our findings will guide strategies to enhance the resistance of cucumber to corynespora leaf spot.

Expression of pathogenesis-related proteins in transplastomic tobacco plants confers resistance to filamentous pathogens under field trials

Plants are continuously challenged by pathogens, affecting most staple crops compromising food security. They have evolved different mechanisms to counterattack pathogen infection, including the accumulation of pathogenesis-related (PR) proteins. These proteins have been implicated in active defense, and their overexpression has led to enhanced resistance in nuclear transgenic plants, although in many cases constitutive expression resulted in lesion-mimic phenotypes. We decided to evaluate plastid transformation as an alternative to overcome limitations observed for nuclear transgenic technologies. The advantages include the possibilities to express polycistronic RNAs, to obtain higher protein expression levels, and the impeded gene flow due to the maternal inheritance of the plastome. We transformed Nicotiana tabacum plastids to co-express the tobacco PR proteins AP24 and β-1,3-glucanase. Transplastomic tobacco lines were characterized and subsequently challenged with Rhizoctonia solani, Peronospora hyoscyami f.sp. tabacina and Phytophthora nicotianae. Results showed that transplastomic plants expressing AP24 and β-1,3-glucanase are resistant to R. solani in greenhouse conditions and, furthermore, they are protected against P.hyoscyami f.sp. tabacina and P. nicotianae in field conditions under high inoculum pressure. Our results suggest that plastid co- expression of PR proteins AP24 and β-1,3-glucanase resulted in enhanced resistance against filamentous pathogens.