Search Results (18)

Nitric oxide and reactive nitrogen species are key signalling molecules with pleiotropic effects in plants. They are crucial elements of the redox regulation of plant stress responses to abiotic and biotic stresses. Nitric oxide is known to enhance photosynthetic efficiency under abiotic stress, and reactive nitrogen species-mediated alterations in photosynthetic metabolism have been shown to confer resistance to abiotic stresses. However, knowledge about the role of reactive nitrogen species in plant immune responses remains limited. In this review, we highlight recent advancements in understanding the role of NO in regulating stomatal movement, which contributes to resistance against pathogens. We will examine the involvement of NO in the regulation of photosynthesis, which provides energy, reducing equivalents and carbon skeletons for defence, as well as the significance of protein S-nitrosylation in relation to immune responses. The role of NO synthesis induced in pathogenic organisms during plant–pathogen interactions, along with S-nitrosylation of pathogen effectors to counteract their pathogenesis-promoting activity, is also reported. We will discuss the progress in understanding the interactions between reactive nitrogen species and photosynthetic metabolism, focusing on enhancing crop plants’ productivity and resistance in challenging environmental conditions. Full article

Chaperonin 60 proteins plays an important role in plant growth and development as well as the response to abiotic stress. As part of the protein homeostasis system, molecular chaperones have attracted increasing attention in recent years due to their involvement in the folding and assembly of key proteins in photosynthesis. However, little is known about the function of maize chaperonin 60 protein. In the study, a gene encoding the chaperonin 60 proteins was cloned from the maize inbred line B73, and named ZmCpn60-3. The gene was 1, 818 bp in length and encoded a protein consisting of 605 amino acids. Phylogenetic analysis showed that ZmCpn60-3 had high similarity with OsCPN60-1, belonging to the β subunits of the chloroplast chaperonin 60 protein family, and it was predicted to be localized in chloroplasts. The ZmCpn60-3 was highly expressed in the stems and tassels of maize, and could be induced by exogenous plant hormones, mycotoxins, and pathogens; Overexpression of ZmCpn60-3 in Arabidopsis improved the resistance to Pst DC3000 by inducing the hypersensitive response and the expression of SA signaling-related genes, and the H₂O₂ and the SA contents of ZmCpn60-3-overexpressing Arabidopsis infected with Pst DC3000 accumulated significantly when compared to the wild-type controls. Experimental data demonstrate that flg22 treatment significantly upregulated transcriptional levels of the PR1 defense gene in ZmCpn60-3-transfected maize protoplasts. Notably, the enhanced resistance phenotype against Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) in ZmCpn60-3-overexpressing transgenic lines was specifically abolished by pretreatment with ABT, a salicylic acid (SA) biosynthetic inhibitor. Our integrated findings reveal that this chaperonin protein orchestrates plant immune responses through a dual mechanism: triggering a reactive oxygen species (ROS) burst while simultaneously activating SA-mediated signaling cascades, thereby synergistically enhancing host disease resistance. Additionally, yeast two-hybrid assay preliminary data indicated that ZmCpn60-3 might bind to ZmbHLH118 and ZmBURP7, indicating ZmCpn60-3 might be involved in plant abiotic responses. The results provided a reference for comprehensively understanding the resistance mechanism of ZmCpn60-3 in plant responses to abiotic or biotic stress. Full article

Ultraviolet C (UV-C) flash treatment represents a promising method for priming plants. This study compared the effects of 1 s (flash) and 60 s (60 s) UV-C exposures on the transcriptome of Arabidopsis thaliana L. plants. A dose of 200 J m⁻² delivered in one second was observed to effectively stimulate plant defenses without causing any adverse effects on plant health. A total of 3054 and 1865 differentially expressed genes (DEGs) were identified in the flash and 60 s treatments, respectively, in comparison to the control plants. Of these, 1131 were common to both treatments. The flash treatment affected a greater number of transcription factors (415 genes) than the 60 s treatment (254 genes), indicating more pronounced alterations in gene expression. The flash treatment resulted in a significant overexpression of heat shock proteins (HSPs), heat shock factors (HSFs), and their associated genes, which impacted oxidative stress, proteostasis, genome stability, cell survival, and thermotolerance. The majority of mitochondrial genes were found to be upregulated, while photosynthetic genes exhibited a downregulation. These expression patterns coordinate electron transport and crosstalk between the nucleus, chloroplasts, and mitochondria, eliciting an adaptive protective response to UV-C flash. Additionally, the flash treatment resulted in alterations to several genes involved in cell cycle regulation, division, and DNA replication. These included ATP BMMs, BRCA2 s, IQDs, kinesin complex, MCM complex, CYCs, and CDKs, which ultimately led to cell cycle arrest as a temporary preparation for subsequent conditions. The present study demonstrates that a 1 s exposure to UV-C induces distinctive plant responses through coordinated gene expression. The findings suggest that the flash treatment is an innovative method that triggers a unique cellular response, prioritizing repair mechanisms and potentially enhancing plant immunity, resilience, and priming. It can be used as a plant resistance inducer and stimulator. Full article

When plants face biotic stress, the induction of defence responses imposes a massive demand for carbon and energy resources, which could decrease the reserves allocated towards growth. These growth–defence trade-offs have important implications for plant fitness and productivity and influence the outcome of plant–pathogen interactions. Biotic stress strongly affects plant cells’ primary metabolism, including photosynthesis and respiration, the main source of energy and carbon skeletons for plant growth, development, and defence. Although the nature of photosynthetic limitations imposed by pathogens is variable, infection often increases photorespiratory pressure, generating conditions that promote ribulose-1,5-bisphosphate oxygenation, leading to a metabolic shift from assimilation to photorespiration. Photorespiration, the significant metabolic flux following photosynthesis, protects the photosynthetic apparatus from photoinhibition. However, recent studies reveal that its role is far beyond photoprotection. The intermediates of the photorespiratory cycle regulate photosynthesis, and photorespiration interacts with the metabolic pathways of nitrogen and sulphur, shaping the primary metabolism for stress responses. This work aims to present recent insights into the integration of photorespiration within the network of primary metabolism under biotic stress. It also explores the potential implications of regulating photosynthetic–photorespiratory metabolism for plant defence against bacterial and fungal pathogens. Full article

Melatonin regulates vital physiological processes in animals, such as the circadian cycle, sleep, locomotion, body temperature, food intake, and sexual and immune responses. In plants, melatonin modulates seed germination, longevity, circadian cycle, photoperiodicity, flowering, leaf senescence, postharvest fruit storage, and resistance against biotic and abiotic stresses. In plants, the effect of melatonin is mediated by various regulatory elements of the redox network, including RNS and ROS. Similarly, the radical gas NO mediates various physiological processes, like seed germination, flowering, leaf senescence, and stress responses. The biosynthesis of both melatonin and NO takes place in mitochondria and chloroplasts. Hence, both melatonin and nitric oxide are key signaling molecules governing their biological pathways independently. However, there are instances when these pathways cross each other and the two molecules interact with each other, resulting in the formation of N-nitrosomelatonin or NOMela, which is a nitrosated form of melatonin, discovered recently and with promising roles in plant development. The interaction between NO and melatonin is highly complex, and, although a handful of studies reporting these interactions have been published, the exact molecular mechanisms governing them and the prospects of NOMela as a NO donor have just started to be unraveled. Here, we review NO and melatonin production as well as RNS–melatonin interaction under normal and stressful conditions. Furthermore, for the first time, we provide highly sensitive, ozone-chemiluminescence-based comparative measurements of the nitric oxide content, as well as NO-release kinetics between NOMela and the commonly used NO donors CySNO and GSNO. Full article

Rice blast, caused by the fungal pathogen Magnaporthe oryzae (M. oryzae), is a highly destructive disease that significantly impacts rice yield and quality. During the infection, M. oryzae secretes effector proteins to subvert the host immune response. However, the interaction between the effector protein AvrPik-D and its target proteins in rice, and the mechanism by which AvrPik-D exacerbates disease severity to facilitate infection, remains poorly understood. In this study, we found that the M. oryzae effector AvrPik-D interacts with the Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) small subunit OsRBCS4. The overexpression of the OsRBCS4 gene in transgenic rice not only enhances resistance to M. oryzae but also induces more reactive oxygen species following chitin treatment. OsRBCS4 localizes to chloroplasts and co-localizes with AvrPik-D within these organelles. AvrPik-D suppresses the transcriptional expression of OsRBCS4 and inhibits Rubisco activity in rice. In conclusion, our results demonstrate that the M. oryzae effector AvrPik-D targets the Rubisco small subunit OsRBCS4 and inhibits its carboxylase and oxygenase activity, thereby suppressing rice innate immunity to facilitate infection. This provides a novel mechanism for the M. oryzae effector to subvert the host immunity to promote infection. Full article

Plant glycerate kinase (GK) was previously considered an exclusively chloroplastic enzyme of the glycolate pathway (photorespiration), and its sole predicted role was to return most of the glycolate-derived carbon (as glycerate) to the Calvin cycle. However, recent discovery of cytosolic GK revealed metabolic links for glycerate to other processes. Although GK was initially proposed as being solely regulated by substrate availability, subsequent discoveries of its redox regulation and the light involvement in the production of chloroplastic and cytosolic GK isoforms have indicated a more refined regulation of the pathways of glycerate conversion. Here, we re-evaluate the importance of GK and emphasize its multifaceted role in plants. Thus, GK can be a major player in several branches of primary metabolism, including the glycolate pathway, gluconeogenesis, glycolysis, and C₄ metabolism. In addition, recently, the chloroplastic (but not cytosolic) GK isoform was implicated as part of a light-dependent plant immune response to pathogen attack. The origins of glycerate are also discussed here; it is produced in several cell compartments and undergoes huge fluctuations depending on light/dark conditions. The recent discovery of the vacuolar glycerate transporter adds yet another layer to our understanding of glycerate transport/metabolism and that of other two- and three-carbon metabolites. Full article

Rice (Oryza sativa L.) is one of the world’s most crucial food crops, as it currently supports more than half of the world’s population. However, the presence of sheath blight (SB) caused by Rhizoctonia solani has become a significant issue for rice agriculture. This disease is responsible for causing severe yield losses each year and is a threat to global food security. The breeding of SB-resistant rice varieties requires a thorough understanding of the molecular mechanisms involved and the exploration of immune genes in rice. To this end, we conducted a screening of rice cultivars for resistance to SB and compared the transcriptome based on RNA-seq between the most tolerant and susceptible cultivars. Our study revealed significant transcriptomic differences between the tolerant cultivar ZhengDao 22 (ZD) and the most susceptible cultivar XinZhi No.1 (XZ) in response to R. solani invasion. Specifically, the tolerant cultivar showed 7066 differentially expressed genes (DEGs), while the susceptible cultivar showed only 60 DEGs. In further analysis, we observed clear differences in gene category between up- and down-regulated expression of genes (uDEGs and dDEGs) based on Gene Ontology (GO) classes in response to infection in the tolerant cultivar ZD, and then identified uDEGs related to cell surface pattern recognition receptors, the Ca²⁺ ion signaling pathway, and the Mitogen-Activated Protein Kinase (MAPK) cascade that play a positive role against R. solani. In addition, DEGs of the jasmonic acid and ethylene signaling pathways were mainly positively regulated, whereas DEGs of the auxin signaling pathway were mainly negatively regulated. Transcription factors were involved in the immune response as either positive or negative regulators of the response to this pathogen. Furthermore, our results showed that chloroplasts play a crucial role and that reduced photosynthetic capacity is a critical feature of this response. The results of this research have important implications for better characterization of the molecular mechanism of SB resistance and for the development of resistant cultivars through molecular breeding methods. Full article

MicroRNAs (miRNAs) have been shown to be critical components in plant immunity. MicroRNA398 (miR398) is a highly conserved miRNA in all land plants and plays crucial roles in diverse biotic stress responses. However, the role of miR398 has not yet been characterized in tomato resistance against Botrytis cinerea. In this report, the transcript levels of sly-miR398b were strongly decreased in B. cinerea-infected leaves and the overexpression of sly-miR398b resulted in enhanced susceptibility. The attenuated expression of cytosol Cu/Zn-SOD (CSD1), chloroplast Cu/Zn-SOD (CSD2), and guaiacol peroxidase (GPOD), as well as the decreased activities of superoxide dismutase (SOD) and GPOD, collectively led to increased hydrogen peroxide (H₂O₂) accumulation in sly-miR398b overexpressing plants. Furthermore, sly-miR398b was induced by methyl jasmonate (MeJA) treatment. The overexpression of sly-miR398b suppressed the expression of TomLoxD, LapA, and PR-STH2 in response to B. cinerea and MeJA treatment. Our data demonstrate that sly-miR398b overexpression negatively regulates the resistance to B. cinerea in tomato by inducing the accumulation of reactive oxygen species (ROS) and downregulating the expression of MeJA-responsive defense genes. Full article

β-Carbonic anhydrase (βCA) is very important for plant growth and development, but its function in immunity has also been examined. In this study, we found that the expression level of Solanum lycopersicum βCA1 (SlβCA1) was significantly upregulated in plants treated with Xanthomonas euvesicatoria 85-10. The protein was localized in the nucleus, cell membrane and chloroplast. Using tomato plants silenced with SlβCA1, we demonstrated that SlβCA1 plays an active role in plant disease resistance. Moreover, we found that the elicitor PopW upregulated the expression of SlβCA1, while the microbe-associated molecular pattern response induced by PopW was inhibited in TRV-SlβCA1. The interaction between PopW and SlβCA1 was confirmed. Here, we found that SlβCA1 was positively regulated during PopW-induced resistance to Xanthomonas euvesicatoria 85-10. These data indicate the importance of SlβCA1 in plant basic immunity and its recognition by the Harpin protein PopW as a new target for elicitor recognition. Full article

Plants that are adapted to harsh environments offer enormous opportunity to understand stress responses in ecological systems. Stipa capillacea is widely distributed in the frigid and arid region of the Tibetan Plateau, but its signal transduction system under cold stress has not been characterized. In this study, we isolated a cDNA encoding the signal transduction protein, ScCBL6, from S. capillacea, and evaluated its role in cold tolerance by ectopically expressing it in Arabidopsis. Full-length ScCBL6 encode 227 amino acids, and are clustered with CBL6 in Stipa purpurea and Oryza sativa in a phylogenetic analysis. Compared with tolerance in wild-type (WT) plants, ScCBL6-overexpressing plants (ScCBL6-OXP) were more tolerant to cold stress but not to drought stress, as confirmed by their high photosynthetic capacity (Fv/Fm) and survival rate under cold stress. We further compared their cold-responsive transcriptome profiles by RNA sequencing. In total, 3931 genes were differentially expressed by the introduction of ScCBL6. These gene products were involved in multiple processes such as the immune system, lipid catabolism, and secondary metabolism. A KEGG pathway analysis revealed that they were mainly enriched in plant hormone signal transduction and biomacromolecule metabolism. Proteins encoded by differentially expressed genes were predicted to be localized in chloroplasts, mitochondria, and vacuoles, suggesting that ScCBL6 exerts a wide range of functions. Based on its tonoplast subcellular location combined with integrated transcriptome and physiological analyses of ScCBL6-OXP, we inferred that ScCBL6 improves plant cold stress tolerance in Arabidopsis via the regulation of photosynthesis, redox status, and tonoplast metabolite transporters. Full article

Pecan leaf-variegated plant, which was infected with a novel badnavirus named pecan mosaic virus (PMV) detected by small RNA deep sequencing, is a vital model plant for studying the molecular mechanism of retaining green or chlorosis of virus-infected leaves. In this report, PMV infection in pecan leaves induced PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). PMV infection suppressed the expressions of key genes of fatty acid, oleic acid (C18:1), and very-long-chain fatty acids (VLCFA) biosynthesis, indicating that fatty acids-derived signaling was one of the important defense pathways in response to PMV infection in pecan. PMV infection in pecans enhanced the expressions of pathogenesis-related protein 1 (PR1). However, the transcripts of phenylalanine ammonia-lyase (PAL) and isochorismate synthase (ICS) were downregulated, indicating that salicylic acid (SA) biosynthesis was blocked in pecan infected with PMV. Meanwhile, disruption of auxin signaling affected the activation of the jasmonic acid (JA) pathway. Thus, C18:1 and JA signals are involved in response to PMV infection in pecan. In PMV-infected yellow leaves, damaged chloroplast structure and activation of mitogen-activated protein kinase 3 (MPK3) inhibited photosynthesis. Cytokinin and SA biosynthesis was blocked, leading to plants losing immune responses and systemic acquired resistance (SAR). The repression of photosynthesis and the induction of sink metabolism in the infected tissue led to dramatic changes in carbohydrate partitioning. On the contrary, the green leaves of PMV infection in pecan plants had whole cell tissue structure and chloroplast clustering, establishing a strong antiviral immunity system. Cytokinin biosynthesis and signaling transductions were remarkably strengthened, activating plant immune responses. Meanwhile, cytokinin accumulation in green leaves induced partial SA biosynthesis and gained comparatively higher SAR compared to that of yellow leaves. Disturbance of the ribosome biogenesis might enhance the resistance to PMV infection in pecan and lead to leaves staying green. Full article

Glomerella leaf spot of apple, caused by Colletotrichumgloeosporioides, is a devastating disease that leads to severe defoliation and fruit spots. The Colletotrichum species secretes a series of effectors to manipulate the host’s immune response, facilitating its colonization in plants. However, the mechanism by which the effector of C. gloeosporioides inhibits the defenses of the host remains unclear. In this study, we reported a novel effector Sntf2 of C. gloeosporioides. The transient expression of SNTF2 inhibits BAX-induced cell death in tobacco plants. Sntf2 suppresses plant defense responses by reducing callose deposition and H₂O₂ accumulation. SNTF2 is upregulated during infection, and its deletion reduces virulence to the plant. Sntf2 is localized to the chloroplasts and interacts with Mdycf39 (a chloroplast PSII assembly factor) in apple leaves. The Mdycf39 overexpression line increases susceptibility to C. gloeosporioides, whereas the Mdycf39 transgenic silent line does not grow normally with pale white leaves, indicating that Sntf2 disturbs plant defense responses and growth by targeting Mdycf39. Full article

One of the earliest hallmarks of plant immune response is production of reactive oxygen species (ROS) in different subcellular compartments, which regulate plant immunity. A suitable equilibrium, which is crucial to prevent ROS overaccumulation leading to oxidative stress, is maintained by salicylic acid (SA), a chief regulator of ROS. However, ROS not only act downstream of SA signaling, but are also proposed to be a central component of a self-amplifying loop that regulates SA signaling as well as the interaction balance between different phytohormones. The exact role of this crosstalk, the position where SA interferes with ROS signaling and ROS interferes with SA signaling and the outcome of this regulation, depend on the origin of ROS but also on the pathosystem. The precise spatiotemporal regulation of organelle-specific ROS and SA levels determine the effectiveness of pathogen arrest and is therefore crucial for a successful immune response. However, the regulatory interplay behind still remains poorly understood, as up until now, the role of organelle-specific ROS and SA in hypersensitive response (HR)-conferred resistance has mostly been studied by altering the level of a single component. In order to address these aspects, a sophisticated combination of research methods for monitoring the spatiotemporal dynamics of key players and transcriptional activity in plants is needed and will most probably consist of biosensors and precision transcriptomics. Full article

Plant epidermis contains atypical small chloroplasts. However, the physiological role of this organelle is unclear compared to that of large mesophyll chloroplasts, the well-known function of which is photosynthesis. Although knowledge of the involvement of chloroplasts in the plant immunity has been expanded to date, the differences between the epidermal and mesophyll chloroplasts are beyond the scope of this study. Given the role of the plant epidermis as a barrier to environmental stresses, including pathogen attacks, and the immune-related function of chloroplasts, plant defense research on epidermal chloroplasts is an emerging field. Recent studies have revealed the dynamic movements of epidermal chloroplasts in response to fungal and oomycete pathogens. Furthermore, epidermal chloroplast-associated proteins and cellular events that are tightly linked to epidermal resistance against pathogens have been reported. In this review, I have focused on the recent progress in epidermal chloroplast-mediated plant immunity. Full article