Defense Pathways Research Articles

Phosphatidylcholine Transfer Protein OsPCTP Interacts with Ascorbate Peroxidase OsAPX8 to Regulate Bacterial Blight Resistance in Rice

Rice phosphatidylcholine transfer protein (PCTP), which contains a steroidogenic acute regulatory protein-related lipid transfer (START) domain, responds to bacterial blight disease. Overexpression of OsPCTP quantitatively enhances resistance to pathogen in rice, whereas depletion of it has the opposite effect. Further analysis showed that OsPCTP physically interacts with OsAPX8, a ROS scavenging enzyme, and influences ascorbate peroxidase enzymatic activity in vivo. In addition, the expression of pathogenesis-related genes PR1a, PR1b and PR10 were significantly induced in OsPCTP-OE plants compared with that in wild-type plants ZH11. Taken together, these results suggested that OsPCTP mediates bacterial blight resistance in rice through regulating the ROS defense pathway.

Drought Tolerance in Plants: Physiological and Molecular Responses

Drought, a significant environmental challenge, presents a substantial risk to worldwide agriculture and the security of food supplies. In response, plants can perceive stimuli from their environment and activate defense pathways via various modulating networks to cope with stress. Drought tolerance, a multifaceted attribute, can be dissected into distinct contributing mechanisms and factors. Osmotic stress, dehydration stress, dysfunction of plasma and endosome membranes, loss of cellular turgidity, inhibition of metabolite synthesis, cellular energy depletion, impaired chloroplast function, and oxidative stress are among the most critical consequences of drought on plant cells. Understanding the intricate interplay of these physiological and molecular responses provides insights into the adaptive strategies plants employ to navigate through drought stress. Plant cells express various mechanisms to withstand and reverse the cellular effects of drought stress. These mechanisms include osmotic adjustment to preserve cellular turgor, synthesis of protective proteins like dehydrins, and triggering antioxidant systems to counterbalance oxidative stress. A better understanding of drought tolerance is crucial for devising specific methods to improve crop resilience and promote sustainable agricultural practices in environments with limited water resources. This review explores the physiological and molecular responses employed by plants to address the challenges of drought stress.

Induced Resistance in Fruit and Vegetable Enhancing Host Defence to Curve Post-harvest Diseases

Induced resistance (IR) is an emerging, environmentally friendly strategy to manage post-harvest diseases in fruits and vegetables by enhancing the plant’s innate immune system. This approach leverages the plant's natural defense mechanisms, including the activation of defense-related enzymes like chitinases, glucanases, and peroxidases, accumulation of secondary metabolites such as phytoalexins and phenolics, and the strengthening of cell walls to prevent pathogen invasion. Additionally, the production of reactive oxygen species (ROS) plays a crucial role in both signaling and direct pathogen inhibition. Despite its potential, the effectiveness of IR varies across different crops and pathogens, and its success is heavily influenced by environmental factors, such as humidity, temperature, and light. There are also concerns regarding possible trade-offs, such as reduced yield or changes in fruit quality due to the diversion of energy towards defense responses. However, the integration of IR with other disease management strategies, including the use of biological control agents and conventional fungicides, has shown promising results in reducing post-harvest losses. Case studies in fruits like apples, tomatoes, and citrus, as well as vegetables like potatoes and peppers, demonstrate the practical applications of IR in commercial agriculture. Advances in genetic engineering are opening new pathways for enhancing IR by manipulating key genes involved in defense pathways, while new formulations and precision agriculture technologies offer greater control and efficiency in IR applications. These innovations, along with optimized post-harvest handling and storage practices, hold the potential to make IR a more reliable and sustainable solution for managing post-harvest diseases. However, ongoing research is necessary to address the variability in effectiveness and to explore long-term sustainability, especially as pathogens evolve and environmental conditions change. Induced resistance, when integrated with a comprehensive disease management approach, offers a significant step forward in reducing post-harvest losses and improving food security globally.

Antiaging in a Bottle: Bioactive Competency of Plasma-Generated Nitric Oxide Water for Modulation of Aging-Related Signature in Human Dermal Cells.

Nitric oxide (NO), a potential therapeutic antiaging molecule, modulates various physiological and cellular processes. However, alterations in endogenous NO levels brought on by aging impact multiple organ systems and heighten susceptibility to age-related skin diseases. This correlation underscores the importance of investigating NO-based antiaging interventions. Nonthermal plasma-generated NO is a promising avenue for cosmetic and regenerative medicine due to its capacity to stimulate cellular growth. Herein, we examine the potential of plasma-generated nitric oxide water (NOW) as a bioactive agent in human dermal fibroblasts, emphasizing gene expression patterns linked to extracellular matrix (ECM) breakdown and cellular senescence. The findings of our study indicate that administering NOW at lower dosages enhances cell migration and proliferation. Moreover, the genetic signatures associated with ECM synthesis, antioxidant defense, and antisenescence pathways have been analyzed in NOW-exposed cells. Notably, the downregulation of ECM-degrading enzyme transcripts─collagenase, elastase, and hyaluronidase─suggests NOW's potential in mitigating the intrinsic skin aging phenomena, emphasizing the promise of NO-based interventions in advancing antiaging strategies within regenerative medicine.

Activation of ATF3 via the integrated stress response pathway regulates innate immune response to restrict Zika virus.

Zika virus (ZIKV) is a re-emerging mosquito-borne flavivirus that co-opts cellular mechanisms to support viral processes that can reprogram the host transcriptional profile. Such viral-directed transcriptional changes and the pro- or anti-viral outcomes remain understudied. We previously showed that ATF3, a stress-induced transcription factor, is significantly upregulated in ZIKV-infected mammalian cells, along with other cellular and immune response genes. We now define the intracellular pathway responsible for ATF3 activation and elucidate the impact of ATF3 expression on ZIKV infection. We show that during ZIKV infection, the integrated stress response pathway stimulates ATF3 which enhances the innate immune response to antagonize ZIKV infection. This study establishes a link between viral-induced stress response and transcriptional regulation of host defense pathways and thus expands our knowledge of virus-mediated transcriptional mechanisms and transcriptional control of interferon-stimulated genes during ZIKV infection.

Burkholderia pseudomallei BopE suppresses the Rab32-dependent defense pathway to promote its intracellular replication and virulence.

Melioidosis is a serious infectious disease caused by the Gram-negative bacterium Burkholderia pseudomallei. Recently, Rab32-dependent immune vesicles emerge as a critical defense pathway to restrict the intracellular B. pseudomallei. However, B. pseudomallei can evade host immune vesicles and survive in the cytoplasm, although this mechanism is not well understood. In this study, we found Rab32-dependent vesicles could effectively combat B. pseudomallei infection, but not all intracellular B. pseudomallei were encapsulated in Rab32-positive vesicles. To explore how B. pseudomallei counteracted the Rab32-dependent defense pathway, transcriptomic profiling of B. pseudomallei was performed to characterize the response dynamics during infection. We found that the type III secretion system of B. pseudomallei was activated, and a variety of effector proteins were highly upregulated. Among them, BopE, BprD, and BipC were shown to interact with Rab32. Interestingly, BopE directly interacts with host Rab32, potentially suppressing Rab32 function by interfering with nucleotide exchange, which in turn restricts the recruitment of Rab32 to bacterial-containing vesicles. Knocking out of BopE can increase the proportion of Rab32-positive vesicles, suppressing the intracellular replication and virulence of B. pseudomallei. Collectively, our findings have demonstrated that BopE may be an important effector for B. pseudomallei to evade from the Rab32-dependent killing vesicles into the cytosol for survival and replication. Therefore, a deeper understanding of the interaction between BopE and the host Rab32-dependent restriction pathway may provide an effective therapeutic strategy for the elimination of intracellular B. pseudomallei.IMPORTANCEB. pseudomallei is facultative intracellular bacterium that has evolved numerous strategies to evade host immune vesicles and survive in the cytoplasm. Rab32-dependent vesicles are one of these immune vesicles, but the mechanism by which B. pseudomallei escape Rab32-dependent vesicles remains elusive. Here, we find B. pseudomallei infection leading the activation of the type III secretion system (T3SS-3) and increasing the expression of various effectors. Specifically, we identify that BopE, an effector secreted by T3SS-3, triggers vesicle escape to promote B. pseudomallei pathogenicity and survival. Mechanistically, BopE suppresses the activation of Rab32 by interfering with nucleotide exchange, ultimately triggering vesicle escape and intracellular survival. We also find knocking out the bopE gene can increase the proportion of Rab32-positive vesicles that trap B. pseudomallei, dampening the survival of B. pseudomallei both in vitro and in vivo. Taken together, our findings provide insights into the molecular mechanisms of pathogen effector-induced vesicle escape, indicating a potential melioidosis treatment via blocking B. pseudomallei BopE-host Rab32 interaction.

Unveiling the Innate and Adaptive Immunity Interplay: Global Transcriptomic Profiling of the Host Immune Response in Candida albicans Endophthalmitis in a Murine Model.

Intraocular fungal infection poses a significant clinical challenge characterized by chronic inflammation along with vision impairment. Understanding the host defense pathways involved in fungal endophthalmitis will play a pivotal role in identifying adjuvant immunotherapy. Clinical isolates of Candida albicans (15,000 CFU/μL) were intravitreally injected in C57BL/6 mice followed by enucleation at 24 and 72 h postinfection. Histopathological analysis was performed to evaluate the retinal changes and the disease severity. RNA-seq analysis was conducted on homogenized eyeballs to assess the relevant gene profiles and their differentially expressed genes (DEGs). Pathway enrichment analysis was performed to further annotate the functions of the DEGs. Histopathological analysis demonstrated a higher disease severity with increased inflammatory cells at 72 hpi and transcriptome analysis revealed 27,717 DEGs, of which 1493 were significant (adj p value ≤0.05, FC ≥ 1.5). Among these, 924 were upregulated, and 569 were downregulated. Majority of the upregulated genes were associated with the inflammatory/host immune response and signal transduction and enriched in the T-cell signaling pathway, natural killer cell-mediated cytotoxicity, C-type receptor signaling pathway, and NOD-like receptor signaling pathway. Furthermore, inflammation-associated genes such as T-cell surface glycoprotein CD3, cathelicidin antimicrobial peptide, and lymphocyte cell-specific protein tyrosine kinase were enriched, while pathways such as MAPK, cAMP, and metabolic pathways were downregulated. Regulating the T-cell influx could be a potential strategy to modulate excessive inflammation in the retina and could potentially aid in better vision recovery in fungal endophthalmitis.

Toxic Effect of Methyl-Thiophanate on Bombyx mori Based on Physiological and Transcriptomic Analysis

Background/Objectives: The utilization of methyl-thiophanate (MT) in vegetables and fruits is widespread due to its broad efficiency, yet its potential impact on silkworm growth remains uncertain. This study aims to examine the effects of MT on the growth of silkworms. Specifically, we assessed the weights of fifth-instar larvae that were fed mulberry leaves saturated with three concentrations (2.5, 5, and 10 mg/mL) of MT, as well as the weights of a control group. Methods: TEM was used to show the status of the silkworm midgut after MT supplementation. Oxidative stress was evaluated in the presence of MT. Furthermore, a transcriptomic sequencing experiment was conducted to investigate the mechanism through which the development of silkworms is induced by MT. Results: Our findings indicate that the supplementation of MT hindered larval growth compared to the control group, suggesting a toxic effect of MT on silkworms. The transmission electron microscopy (TEM) results show that MT supplementation induced autophagy in the silkworm midgut. MT was also found to induce oxidative stress in silkworms through the activation of reactive oxygen (ROS), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities. Subsequent transcriptomic analysis revealed 1265 significantly differentially expressed genes (DEGs) in response to MT. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that these DEGs were associated with antioxidant defense, detoxification processes, lysosome biogenesis, and metabolic pathways. Conclusions: These findings suggest that MT toxicity in silkworm larvae is mediated through the induction of oxidative stress and alterations in metabolism. This study contributes to our understanding of the impacts of MT exposure on silkworms and provides insights into potential pesticides for use in mulberry gardens.

DbGTi protein attenuates chromium (VI)-induced oxidative stress via activation of the Nrf2/HO-1 signalling pathway in zebrafish (Danio rerio) larval model

Hexavalent chromium (Cr (VI)) contamination poses a significant threat to environmental and human health due to its ability to induce oxidative stress. Conventional strategies to counter Cr (VI)-induced oxidative stress, like antioxidants and chelating agents, face efficacy limitations and adverse effects. The present study is intended to counteract the limitations of conventional strategies by introducing a trypsin inhibitor isolated from Dioscorea bulbifera L. tubers, known as DbGTi protein, against Cr (VI)-induced developmental toxicity and oxidative stress. Through a comprehensive array of biochemical assays, behavioural tests, and gene expression analyses, this study interprets the underlying mechanisms of the DbGTi protein. Results demonstrated that the DbGTi protein effectively restored antioxidant defense systems, including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione S-transferase (GST), and glutathione peroxidase (GTPx), thereby mitigating cellular damage, reducing cell death, and enhancing neuro-biomarkers. qRT-PCR analysis of mRNA expression profiling revealed the upregulation of genes associated with antioxidant defense (sod, cat, gpx) and defense pathway (nrf2, hmox-1a), further highlighting the protective effects of DbGTi protein against Cr (VI)-induced oxidative stress.

Pregnancy enhances antiviral immunity independent of type I IFN but dependent on IL-17-producing γδ+ T cells in the nasal mucosa.

Pregnancy is associated with profound changes in immunity. However, pregnancy-related respiratory immune adaptations in response to influenza infection and their impact on disease severity remain unclear. Here, we describe, in a preclinical model of mid-gestation pregnancy, a mechanism of enhanced host defense against influenza A virus (IAV) localized to the nasal cavity that limits viral replication and reduces the magnitude of intrapulmonary immune responses. Consequently, the pregnant mice show reduced pulmonary pathology and preserved airway function after IAV infection. The early restriction of viral replication is independent of type I interferon (IFN) but dependent on increased antimicrobial peptides (AMPs) driven by interleukin-17+ (IL-17+) γδ+ T cells within the nasal passages. This pathway of host defense against IAV infection in the upper airways during pregnancy restricts early viral infection and prevents virus dissemination into the lung supporting maternal fitness.

Airspaces-derived exosomes contain disease-relevant protein signatures in a mouse model of cystic fibrosis (CF)-like mucoinflammatory lung disease.

Exosomes, membrane-bound extracellular vesicles, ranging from approximately 30-200nm in diameter, are released by almost all cell types and play critical roles in intercellular communication. In response to the prevailing stress, the exosome-bound protein signatures vary in abundance and composition. To identify the bronchoalveolar lavage fluid (BALF) exosome-bound proteins associated with mucoinflammatory lung disease and to gain insights into their functional implications, we compared BALF exosomes-derived proteins from adult Scnn1b transgenic (Scnn1b-Tg+) and wild type (WT) mice. A total of 3,144 and 3,119 proteins were identified in BALF exosomes from Scnn1b-Tg+ and WT mice, respectively. Using cutoff criteria (Log2 fold-change > 1 and adjusted p-value < 0.05), the comparison of identified proteins revealed 127 and 30 proteins that were significantly upregulated and downregulated, respectively, in Scnn1b-Tg+ versus WT mice. In addition, 52 and 27 proteins were exclusively enriched in Scnn1b-Tg+ and WT mice, respectively. The identified exosome-bound proteins from the homeostatic airspaces of WT mice were mostly relevant to the normal physiological processes. The protein signatures enriched in the BALF exosomes of Scnn1b-Tg+ mice were relevant to macrophage activation and mucoinflammatory processes. Ingenuity pathway analyses revealed that the enriched proteins in Scnn1b-Tg+ mice contributed to the inflammatory responses and antimicrobial defense pathways. Selective proteins including, RETNLA/FIZZ1, LGALS3/Galectin-3, S100A8/MRP8, and CHIL3/YM1 were immunolocalized to specific cell types. The comparative analysis between enriched BALF exosome proteins and previously identified differentially upregulated genes in Scnn1b-Tg+ versus WT mice suggested that the compartment-/cell-specific upregulation in gene expression dictates the enrichment of their respective proteins in the lung airspaces. Taken together, this study demonstrates that the BALF exosome-bound protein signatures reflect disease-relevant disturbances. Our findings suggest that the exosomes carry disease-relevant protein signatures that can be used as a diagnostic as well as predictive biomarkers for mucoinflammatory lung disease.

Maintaining KEAP1 levels in retinal pigment epithelial cells preserves their viability during prolonged exposure to artificial blue light

Exposure to artificial blue light, one of the most energetic forms of visible light, can increase oxidative stress in retinal cells, potentially enhancing the risk of macular degeneration. Retinal pigment epithelial (RPE) cells play a crucial role in this process; the loss of RPE cells is the primary pathway through which retinal degeneration occurs. In RPE cells, Kelch-like ECH-associated protein 1 (KEAP1) is located in both the nucleus and cytosol, where it binds to nuclear factor erythroid 2-related factor 2 (NRF2) and p62 (sequestosome-1), respectively. Blue light exposure activates the NRF2-heme oxygenase 1 (HMOX1) axis through both canonical and noncanonical p62 pathways thereby reducing oxidative damage, and initiates autophagy, which helps remove damaged proteins. These protective responses may support the survival of RPE cells. However, extended exposure to blue light drastically decreases the viability of RPE cells. This exposure diminishes the ability of KEAP1 to bind to p62 and reduces the level of KEAP1. Inhibition of autophagy does not prevent KEAP1 degradation, the NRF2-HMOX1 axis, or blue-light-induced cytotoxicity. However, proteasome inhibitor along with a transient increase in the amount of KEAP1 in RPE cells, partially restores the p62-KEAP1 complex and reduces blue-light-induced cytotoxicity. In vivo studies confirmed the downregulation of KEAP1 in damaged RPE cells. Mice subjected to periodic blue light exposure exhibited significant atrophy in the outer retina, particularly in the peripheral areas. Additionally, there was a significant decrease in c-wave electroretinography and pupillary light reflex, indicating functional impairments in both visual and nonvisual physiological processes. These data underscore the essential role of KEAP1 in managing oxidative defense and autophagy pathways triggered by blue light exposure in RPE cells.

Transcriptomic and coexpression network analyses revealed the regulatory mechanism of Cydia pomonella infestation on the synthesis of phytohormones in walnut husks

The codling moth (Cydia pomonella) has a major effect on the quality and yield of walnut fruit. Plant defences respond to insect infestation by activating hormonal signalling and the flavonoid biosynthetic pathway. However, little is known about the role of walnut husk hormones and flavonoid biosynthesis in response to C. pomonella infestation. The phytohormone content assay revealed that the contents of salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), jasmonic acid-isoleucine conjugate (JA-ILE), jasmonic acid-valine (JA-Val) and methyl jasmonate (MeJA) increased after feeding at different time points (0, 12, 24, 36, 48, and 72 h) of walnut husk. RNA-seq analysis of walnut husks following C. pomonella feeding revealed a temporal pattern in differentially expressed genes (DEGs), with the number increasing from 3,988 at 12 h to 5,929 at 72 h postfeeding compared with the control at 0 h postfeeding. Walnut husks exhibited significant upregulation of genes involved in various defence pathways, including flavonoid biosynthesis (PAL, CYP73A, 4CL, CHS, CHI, F3H, ANS, and LAR), SA (PAL), ABA (ZEP and ABA2), and JA (AOS, AOC, OPR, JAZ, and MYC2) pathways. Three gene coexpression networks that had a significant positive association with these hormonal changes were constructed based on the basis of weighted gene coexpression network analysis (WGCNA). We identified several hub transcription factors, including the turquoise module (AIL6, MYB4, PRE6, WRKY71, WRKY31, ERF003, and WRKY75), the green module (bHLH79, PCL1, APRR5, ABI5, and ILR3), and the magenta module (ERF27, bHLH35, bHLH18, TIFY5A, WRKY31, and MYB44). Taken together, these findings provide useful genetic resources for exploring the defence response mediated by phytohormones in walnut husks.

The Past, Present, and Future of Plant Activators Targeting the Salicylic Acid Signaling Pathway.

Plant activators have emerged as promising alternatives to conventional crop protection chemicals for managing crop diseases due to their unique mode of action. By priming the plant's innate immune system, these compounds can induce disease resistance against a broad spectrum of pathogens without directly inhibiting their proliferation. Key advantages of plant activators include prolonged defense activity, lower effective dosages, and negligible risk of pathogen resistance development. Among the various defensive pathways targeted, the salicylic acid (SA) signaling cascade has been extensively explored, leading to the successful development of commercial activators of systemic acquired resistance, such as benzothiadiazole, for widespread application in crop protection. While the action sites of many SA-targeting activators have been preliminarily mapped to different steps along the pathway, a comprehensive understanding of their precise mechanisms remains elusive. This review provides a historical perspective on plant activator development and outlines diverse screening strategies employed, from whole-plant bioassays to molecular and transgenic approaches. We elaborate on the various components, biological significance, and regulatory circuits governing the SA pathway while critically examining the structural features, bioactivities, and proposed modes of action of classical activators such as benzothiadiazole derivatives, salicylic acid analogs, and other small molecules. Insights from field trials assessing the practical applicability of such activators are also discussed. Furthermore, we highlight the current status, challenges, and future prospects in the realm of SA-targeting activator development globally, with a focus on recent endeavors in China. Collectively, this comprehensive review aims to describe existing knowledge and provide a roadmap for future research toward developing more potent plant activators that enhance crop health.

Early diagnosis, monitoring, profiling, and management of bayberry twig blight disease by nitrogen metabolism

Pestalotiopsis versicolor, pathogen of Bayberry Twig Blight Disease causes wilt and leaf spots thereby reducing the photosynthetic area which ultimately leads to production of small fruits with poor nutritional quality. Due to heavy dependence on chemicals with its detrimental effect, new biofriendly measures are sort. Surface-enhanced Raman scattering technology was used in early discovery and monitoring of the disease progression in bayberry seedlings. The spectra 1454.46 cm−1 was inferred as the fingerprint of the fungus. MgO nano-bioprotectant (MgONBs) antifungal mechanism of action was studied via transcriptomic and metabolomic profiling at 12 and 24 h post-inoculation (hpi) with P. versicolor and metagenomics profiling at 7 and 14 days post-inoculation (dpi) with P. versicolor. MgONBs enhanced the recruitment of Bradyrhizobium to overcome the attack of P. versicolor. Nitrogen fixation activities in the diseased leaves at 7 and 14 dpi were significantly reduced, while it was significantly increased from 17.74 % in the diseased leaves to 26.79 % in the diseased leaves treated with MgONBs at 14 dpi. Thus, activating bayberry defense by increasing its nitrogen metabolism. In addition, in MgONBs group compared to control, urea, L-Methionine sulfone, and 5-Aminosalicylic acid compounds were activated which enriched its defense and signaling pathways. Upregulated differentially expressed genes in MgONBs relative to the control at 12 and 24 hpi mapped to KEGG pathways involved in amino acid metabolism which was tightly linked to photosynthesis gene (CJ030_MR1G012863). Our results reveals the mechanism of action of MgONBs in combatting phytopathogens.

Low-dose of oligosaccharins boosts antiviral immunity through induction of multiple defense pathways in rice

Oligosaccharins, widely recognized as plant immunity inducers, have been applied and studied for enhancing antiviral defenses in rice over the years. However, due to the complex induction mechanism in rice, further studies are needed. In this study, we demonstrated that oligosaccharins enhanced rice resistance to southern rice black-streaked dwarf virus (SRBSDV) at both the symptomatic and molecular levels. RNA-seq analysis revealed that oligosaccharins enhanced rice antiviral defense by activating multiple defense pathways. Among them, the jasmonic acid (JA) signaling pathway, a crucial antiviral pathway in rice, was investigated in detail. Interestingly, RNA-seq data showed that genes related to JA signaling pathway were significantly induced after 1 h but not after 24 h of oligosaccharins treatment, suggesting that JA induction by oligosaccharins was rapid and sensitive. Furthermore, JA levels and sensitivity analysis showed that oligosaccharins induced JA accumulation, making treated rice plants more sensitive to methyl jasmonate (MeJA). Additionally, oligosaccharins treatment also induced a burst of reactive oxygen species (ROS) in rice. Notably, oligosaccharins demonstrated a low-dose effect, within a certain dilution range from 6000-fold to 1000-fold diluted solution of 5% oligosaccharins, with the 4000-fold diluted solution exhibiting a stronger ability to induce elevated production of JA and ROS. Moreover, the application of low-dose oligosaccharins also enhanced rice resistance to SRBSDV. These data suggest that low-dose of oligosaccharins can enhance rice antiviral defense by inducing multiple defense pathways, including the JA signaling pathway and ROS production.

Abstract C018: Targeting KRAS inhibitor resistance by ferroptosis induction in PDAC

Abstract KRAS inhibitors (KRASi) have shown promising antitumor activity in PDAC patients; however, intrinsic and acquired resistance will likely preclude durable monotherapy responses in the clinic. Genetic and pharmacologic targeting of the KRAS pathway is associated with transcriptional and metabolic adaptations, including epithelial-to-mesenchymal transition (EMT) and dysregulated iron homeostasis that contribute to resistance. Therapy resistant mesenchymal cancer cells have a high reliance on iron that increases their susceptibility to ferroptosis, an iron-dependent form of cell death characterized by generation of lipid reactive oxygen species (ROS). We hypothesize that KRASi resistance characterized by EMT can be overcome by ferroptosis induction in PDAC. Here, we use in vitro and ex vivo PDAC models and transcriptomic and proteomic profiling to define critical ferroptotic liabilities in KRASi-treated PDAC. First, we evaluated the effect of inhibiting different ferroptosis defense mechanisms (e.g. SLC7A11, GPX4, FSP1) using newly developed ferroptosis inducers (FINs) in a panel of epithelial and mesenchymal PDAC cells. Mesenchymal cells were more sensitive to ferroptosis induction compared to epithelial cells. Since ferroptotic death is regulated by multiple ferroptosis defense pathways, and in general PDAC are relatively resistant to ferroptosis induction, it is unlikely that a single ferroptosis inducer will be successful. Therefore, targeting multiple nodes with FINs in a combinatorial approach may lead to a more pronounced effect. Combination GPX4 and SLC7A11 inhibition and GPX4 and FSP1 inhibition were the most effective combinations compared to respective monotherapies. Next, we evaluated if combination of KRASi and ferroptosis induction is synergistic. Transcriptomic analysis of KRAS-mutant PDAC cell lines sensitive or with a priori resistance to KRASi revealed that EMT-related gene sets were upregulated in KRASi resistant cell lines. Quantitative proteomics revealed that PDAC cells treated long-term with KRASi undergo EMT and likewise long-term KRASi in in vivo PDAC models induces EMT. A KRASi-anchored CRISPR/Cas9 screen showed that sgRNAs targeting GPX4 dropped out in multiple cell lines indicating that ferroptosis induction may be synergistic upon KRAS inhibition. Remarkably, KRASi induced an increase of lipid peroxidation levels in PDAC cells which was rescued with antioxidant ferrostatin-1. We also observed that previously generated KRASi resistant cells were more sensitive to GPX4 inhibition. Combination of GPX4 inhibitor with KRASi led to a synergistic effect on cell viability and a significantly higher level of lipid peroxidation compared to monotherapy. These findings highlight the importance of investigating ferroptosis induction as a novel strategy to overcome therapeutic resistance in KRAS-mutant PDAC. We aim to further evaluate these combinations in vivo to determine the best combinatorial strategies in PDAC to prevent or circumvent KRASi resistance. Citation Format: Aparna Padhye, Qijia Yu, Nicole Sindoni, Huan Zhang, Julien Dilly, Hanrong Feng, Andrew Aguirre, Joseph Mancias. Targeting KRAS inhibitor resistance by ferroptosis induction in PDAC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C018.

Exploring the role of FAT genes in Solanaceae species through genome-wide analysis and genome editing.

Plants produce numerous fatty acid derivatives, and some of these compounds have significant regulatory functions, such as governing effector-induced resistance, systemic resistance, and other defense pathways. This study systematically identified and characterized eight FAT genes (Acyl-acyl carrier protein thioesterases), four in the Solanum lycopersicum and four in the Solanum tuberosum genome. Phylogenetic analysis classified these genes into four distinct groups, exhibiting conserved domain structures across different plant species. Promoter analysis revealed various cis-acting elements, most of which are associated with stress responsiveness and growth and development. Micro-RNA (miRNA) analysis identified specific miRNAs, notably miRNA166, targeting different FAT genes in both species. Utilizing clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9)-mediated knockout, mutant lines for SlFATB1 and SlFATB3 were successfully generated and exhibited diverse mutation types. Biochemical evaluation of selected mutant lines revealed significant changes in fatty acid composition, with linoleic and linolenic acid content variations. The study also explored the impact of FAT gene knockout on tomato leaf architecture through scanning electron microscopy, providing insights into potential morphological alterations. Knocking out of FAT genes resulted in a significant reduction in both trichome and stoma density. These findings contribute to a comprehensive understanding of FAT genes in Solanaceous species, encompassing genetic, functional, and phenotypic aspects.

Research progress on plant stress-associated protein (SAP) family: Master regulators to deal with environmental stresses.

Every year, unfavorable environmental factors significantly affect crop productivity and threaten food security. Plants are sessile; they cannot move to escape unfavorable environmental conditions, and therefore, they activate a variety of defense pathways. Among them are processes regulated by stress-associated proteins (SAPs). SAPs have a specific zinc finger domain (A20) at the N-terminus and either AN1 or C2H2 at the C-terminus. SAP proteins are involved in many biological processes and in response to various abiotic or biotic constraints. Most SAPs play a role in conferring transgenic stress resistance and are stress-inducible. The emerging field of SAPs in abiotic or biotic stress response regulation has attracted the attention of researchers. Although SAPs interact with various proteins to perform their functions, the exact mechanisms of these interactions remain incompletely understood. This review aims to provide a comprehensive understanding of SAPs, covering their diversity, structure, expression, and subcellular localization. SAPs play a pivotal role in enabling crosstalk between abiotic and biotic stress signaling pathways, making them essential for developing stress-tolerant crops without yield penalties. Collectively, understanding the complex regulation of SAPs in stress responses can contribute to enhancing tolerance against various environmental stresses through several techniques such as transgenesis, classical breeding, or gene editing.

Unravelling the secrets of soil microbiome and climate change for sustainable agroecosystems.

The soil microbiota exhibits an important function in the ecosystem, and its response to climate change is of paramount importance for sustainable agroecosystems. The macronutrients, micronutrients, and additional constituents vital for the growth of plants are cycled biogeochemically under the regulation of the soil microbiome. Identifying and forecasting the effect of climate change on soil microbiomes and ecosystem services is the need of the hour to address one of the biggest global challenges of the present time. The impact of climate change on the structure and function of the soil microbiota is a major concern, explained by one or more sustainability factors around resilience, reluctance, and rework. However, the past research has revealed that microbial interventions have the potential to regenerate soils and improve crop resilience to climate change factors. The methods used therein include using soil microbes' innate capacity for carbon sequestration, rhizomediation, bio-fertilization, enzyme-mediated breakdown, phyto-stimulation, biocontrol of plant pathogens, antibiosis, inducing the antioxidative defense pathways, induced systemic resistance response (ISR), and releasing volatile organic compounds (VOCs) in the host plant. Microbial phytohormones have a major role in altering root shape in response to exposure to drought, salt, severe temperatures, and heavy metal toxicity and also have an impact on the metabolism of endogenous growth regulators in plant tissue. However, shelf life due to the short lifespan and storage time of microbial formulations is still a major challenge, and efforts should be made to evaluate their effectiveness in crop growth based on climate change. This review focuses on the influence of climate change on soil physico-chemical status, climate change adaptation by the soil microbiome, and its future implications.