A persulfidation-based reversible post-translational modification of Cys desulfhydrase and NADPH oxidase RBOHD fine-tunes guard cell ABA signaling.

Perception of pathogen/microbial-associated molecular patterns (P/MAMPs) by plant cell surface receptors leads to a sustained burst of reactive oxygen species (ROS), a key feature of P/MAMP-triggered immunity (PTI). Here we report that P/MAMP recognition leads to a rapid nitrosative burst, initiating the accumulation of nitric oxide (NO), subsequently leading to S -nitrosylation of the receptor-like cytoplasmic kinase (RLCK), botrytis-induced kinase 1 (BIK1), at Cys ⁸⁰ . This redox-based, posttranslational modification, promotes the phosphorylation of BIK1, subsequently resulting in BIK1 activation and stabilization. Further, BIK1 S -nitrosylation increases its physical interaction with RBOHD, the source of the apoplastic oxidative burst, promoting ROS formation. Our data identify mechanistic links between rapid NO accumulation and the expression of PTI, providing insights into plant immunity.

As a gaseous biological signaling molecule, nitric oxide (NO) regulates many physiological processes in plants. Over the last decades, this low molecular weight compound has been identified as a key signaling molecule to regulate plant stress responses, and also plays an important role in plant development. However, elucidation of the molecular mechanisms for NO in leaf development has so far been limited due to a lack of mutant resources. Here, we employed the NO-deficient mutant nia1nia2 to examine the role of NO in leaf development. We have found that nia1nia2 mutant plants displayed very different leaf phenotypes as compared to wild type Col-0. Further studies have shown that reactive oxygen species (ROS) levels are higher in nia1nia2 mutant plants. Interestingly, ROS-related enzymes ascorbate peroxidase (APX), catalases (CAT), and peroxidases (POD) have shown decreases in their activities. Our transcriptome data have revealed that the ROS synthesis gene RBOHD was enhanced in nia1nia2 mutants and the photosynthesis-related pathway was impaired, which suggests that NO is required for chloroplast development and leaf development. Together, these results imply that NO plays a significant role in plant leaf development by regulating ROS homeostasis.

Summary: Nitric oxide (NO) regulates the deployment of a phalanx of immune responses, chief among which is the activation of a constellation of defence‐related genes. However, the underlying molecular mechanisms remain largely unknown. The Arabidopsis thaliana zinc finger transcription factor (ZF‐TF), S‐nitrosothiol (SNO) Regulated 1 (SRG1), is a central target of NO bioactivity during plant immunity. Here we characterize the remaining members of the SRG gene family. Both SRG2 and, especially, SRG3 were positive regulators of salicylic acid‐dependent plant immunity. Analysis of SRG single, double and triple mutants implied that SRG family members have additive functions in plant immunity and, surprisingly, are under reciprocal regulation. SRG2 and SRG3 localized to the nucleus and functioned as ethylene‐responsive element binding factor‐associated amphiphilic repression (EAR) domain‐dependent transcriptional repressors: NO abolished this activity for SRG3 but not for SRG2. Consistently, loss of GSNOR function, resulting in increased (S)NO concentrations, fully suppressed the disease resistance phenotype established from SRG3 but not SRG2 overexpression. Remarkably, SRG3 but not SRG2 was S‐nitrosylated in vitro and in vivo. Our findings suggest that the SRG family has separable functions in plant immunity, and, surprisingly, these ZF‐TFs exhibit reciprocal regulation. It is remarkable that, through neofunctionalization, the SRG family has evolved to become differentially regulated by the key immune‐related redox cue, NO.

Phytophthora species can infect hundreds of different plants, including many important crops, causing a number of agriculturally relevant diseases. A key feature of attempted pathogen infection is the rapid production of the redox active molecule nitric oxide (NO). However, the potential role(s) of NO in plant resistance against Phytophthora is relatively unexplored. Here we show that the level of NO accumulation is crucial for basal resistance in Arabidopsis against Phytophthora parasitica. Counterintuitively, both relatively low or relatively high NO accumulation leads to reduced resistance against P. parasitica. S‐nitrosylation, the addition of a NO group to a protein cysteine thiol to form an S‐nitrosothiol, is an important route for NO bioactivity and this process is regulated predominantly by S‐nitrosoglutathione reductase 1 (GSNOR1). Loss‐of‐function mutations in GSNOR1 disable both salicylic acid accumulation and associated signalling, and also the production of reactive oxygen species, leading to susceptibility towards P. parasitica. Significantly, we also demonstrate that secreted proteins from P. parasitica can inhibit Arabidopsis GSNOR1 activity.

Chronic inflammation and oxidative stress are pivotal drivers of pathological conditions, necessitating safer plant-derived therapeutic alternatives. This study elucidates the anti-inflammatory and antioxidant mechanisms of Nymphaea “Eldorado” flower water extract (NEWE) in a zebrafish (Danio rerio) model of copper sulfate (CuSO₄)-induced inflammation. NEWE (25–100 μg/mL) attenuates CuSO₄-triggered neutrophil migration and oxidative stress by downregulating proinflammatory genes (il1b, ptgs2a/b) and reducing reactive oxygen species (ROS) production. Transcriptomic profiling identified 339 differentially expressed genes (DEGs), enriched in cytokine signaling and redox regulation, with serpine1, stat3, and mmp9 emerging as key regulatory hubs. Widely targeted metabolomics revealed 891 bioactive compounds, including flavonoids and phenylpropanoids, with network pharmacology predicting multi-target interactions involving inflammatory and oxidative stress pathways. Molecular docking confirmed binding affinities between protocatechuic acid, L-pyroglutamic acid, and Serpine1’s active site, indicating direct interference with inflammation modulation. Collectively, these results establish NEWE as a polypharmacological agent that disrupts inflammation-oxidative stress crosstalk primarily through Serpine1-mediated pathways, offering a molecular foundation for plant-derived interventions against chronic inflammatory diseases.