More Like this

1. Multi-Omics Revealed Molecular Mechanisms Underlying Guard Cell Systemic Acquired Resistance

   https://doi.org/10.3390/ijms22010191  

   David, Lisa ; Kang, Jianing ; Dufresne, Daniel ; Zhu, Dan ; Chen, Sixue ( January 2021 , International Journal of Molecular Sciences)

   Systemic Acquired Resistance (SAR) improves immunity of plant systemic tissue after local exposure to a pathogen. Guard cells that form stomatal pores on leaf surfaces recognize bacterial pathogens via pattern recognition receptors, such as Flagellin Sensitive 2 (FLS2). However, how SAR affects stomatal immunity is not known. In this study, we aim to reveal molecular mechanisms underlying the guard cell response to SAR using multi-omics of proteins, metabolites and lipids. Arabidopsis plants previously exposed to pathogenic bacteria Pseudomonas syringae pv. tomato DC3000 (Pst) exhibit an altered stomatal response compared to control plants when they are later exposed to the bacteria. Reduced stomatal apertures of SAR primed plants lead to decreased number of bacteria in leaves. Multi-omics has revealed molecular components of SAR response specific to guard cells functions, including potential roles of reactive oxygen species (ROS) and fatty acid signaling. Our results show an increase in palmitic acid and its derivative in the primed guard cells. Palmitic acid may play a role as an activator of FLS2, which initiates stomatal immune response. Improved understanding of how SAR signals affect stomatal immunity can aid biotechnology and marker-based breeding of crops for enhanced disease resistance.
2. Natural variation for unusual host responses and flagellin‐mediated immunity against Pseudomonas syringae in genetically diverse tomato accessions

   https://doi.org/10.1111/nph.15788  

   Roberts, Robyn ; Mainiero, Samantha ; Powell, Adrian F. ; Liu, Alexander E. ; Shi, Kai ; Hind, Sarah R. ; Strickler, Susan R. ; Collmer, Alan ; Martin, Gregory B. ( April 2019 , New Phytologist)

   The interaction between tomato andPseudomonas syringaepv tomato (Pst) is a well‐developed model for investigating the molecular basis of the plant immune system. There is extensive natural variation inSolanum lycopersicum(tomato) but it has not been fully leveraged to enhance our understanding of the tomato–Pstpathosystem. We screened 216 genetically diverse accessions of cultivated tomato and a wild tomato species for natural variation in their response to three strains ofPst.

   The host response toPstwas investigated using multiplePststrains, tomato accessions with available genome sequences, reactive oxygen species (ROS) assays, reporter genes and bacterial population measurements.

   The screen uncovered a broad range of previously unseen host symptoms in response toPst, and one of these, stem galls, was found to be simply inherited. The screen also identified tomato accessions that showed enhanced responses to flagellin in bacterial population assays and in ROS assays upon exposure to flagellin‐derived peptides, flg22 and flgII‐28. Reporter genes confirmed that the host responses were due primarily to pattern recognition receptor‐triggered immunity.

   This study revealed extensive natural variation in tomato for susceptibility and resistance toPstand will enable elucidation of the molecular mechanisms underlying these host responses.
3. DYNAMIN-RELATED PROTEIN DRP1A functions with DRP2B in plant growth, flg22-immune responses, and endocytosis

   https://doi.org/10.1093/plphys/kiab024  

   Ekanayake, Gayani ; Smith, John M ; Jones, Kody B ; Stiers, Hayley M ; Robinson, Samuel J ; LaMontagne, Erica D ; Kostos, Paxton H ; Cornish, Peter V ; Bednarek, Sebastian Y ; Heese, Antje ( February 2021 , Plant Physiology)

   Abstract Ligand-induced endocytosis of the immune receptor FLAGELLIN SENSING2 (FLS2) is critical for maintaining its proper abundance in the plasma membrane (PM) to initiate and subsequently down regulate cellular immune responses to bacterial flagellin or flg22-peptide. The molecular components governing PM abundance of FLS2, however, remain mostly unknown. Here, we identified Arabidopsis (Arabidopsis thaliana) DYNAMIN-RELATED PROTEIN1A (DRP1A), a member of a plant-specific family of large dynamin GTPases, as a critical contributor to ligand-induced endocytosis of FLS2 and its physiological roles in flg22-signaling and immunity against Pseudomonas syringae pv. tomato DC3000 bacteria in leaves. Notably, drp1a single mutants displayed similar flg22-defects as those previously reported for mutants in another dynamin-related protein, DRP2B, that was previously shown to colocalize with DRP1A. Our study also uncovered synergistic roles of DRP1A and DRP2B in plant growth and development as drp1a drp2b double mutants exhibited severely stunted roots and cotyledons, as well as defective cell shape, cytokinesis, and seedling lethality. Furthermore, drp1a drp2b double mutants hyperaccumulated FLS2 in the PM prior to flg22-treatment and exhibited a block in ligand-induced endocytosis of FLS2, indicating combinatorial roles for DRP1A and DRP1B in governing PM abundance of FLS2. However, the increased steady-state PM accumulation of FLS2 in drp1amore »drp2b double mutants did not result in increased flg22 responses. We propose that DRP1A and DRP2B are important for the regulation of PM-associated levels of FLS2 necessary to attain signaling competency to initiate distinct flg22 responses, potentially through modulating the lipid environment in defined PM domains.« less
4. Many rice genes are differentially spliced between roots and shoots but cytokinin has minimal effect on splicing

   https://doi.org/10.1002/pld3.136  

   Freese, Nowlan H. ; Estrada, April R. ; Blakley, Ivory C. ; Duan, Jinjie ; Loraine, Ann E. ( May 2019 , Plant Direct)

   Alternatively spliced genes produce multiple spliced isoforms, called transcript variants. In differential alternative splicing, transcript variant abundance differs across sample types. Differential alternative splicing is common in animal systems and influences cellular development in many processes, but its extent and significance is not as well known in plants. To investigate differential alternative splicing in plants, we examined RNA‐Seq data from rice seedlings. The data included three biological replicates per sample type, approximately 30 million sequence alignments per replicate, and four sample types: roots and shoots treated with exogenous cytokinin delivered hydroponically or a mock treatment. Cytokinin treatment triggered expression changes in thousands of genes but had negligible effect on splicing patterns. However, many genes were differentially spliced between mock‐treated roots and shoots, indicating that our methods were sufficiently sensitive to detect differential splicing between data sets. Quantitative fragment analysis of reverse transcriptase‐PCR products made from newly prepared rice samples confirmed 9 of 10 differential splicing events between rice roots and shoots. Differential alternative splicing typically changed the relative abundance of splice variants that co‐occurred in a data set. Analysis of a similar (but less deeply sequenced) RNA‐Seq data set fromArabidopsisshowed the same pattern. In both theArabidopsisand rice RNA‐Seq datamore »sets, most genes annotated as alternatively spliced had small minor variant frequencies. Of splicing choices with abundant support for minor forms, most alternative splicing events were located within the protein‐coding sequence and maintained the annotated reading frame. A tool for visualizing protein annotations in the context of genomic sequence (ProtAnnot) together with a genome browser (Integrated Genome Browser) were used to visualize and assess effects of differential splicing on gene function. In general, differentially spliced regions coincided with conserved protein domains, indicating that differential alternative splicing is likely to affect protein function between root and shoot tissue in rice.

   « less
5. The Pseudomonas syringae type III effector HopG1 triggers necrotic cell death that is attenuated by AtNHR2B

   https://doi.org/10.1038/s41598-022-09335-1  

   Rodríguez-Puerto, Catalina ; Chakraborty, Rupak ; Singh, Raksha ; Rocha-Loyola, Perla ; Rojas, Clemencia M. ( December 2022 , Scientific Reports)

   Abstract The plant pathogenic bacterium Pseudomonas syringae pv. tomato DC3000 ( Pst DC3000) has become a paradigm to investigate plant-bacteria interactions due to its ability to cause disease in the model plant Arabidopsis thaliana. Pst DC3000 uses the type III secretion system to deliver type III secreted effectors (T3SEs) directly into the plant cytoplasm. Pst DC3000 T3SEs contribute to pathogenicity by suppressing plant defense responses and targeting plant’s physiological processes. Although the complete repertoire of effectors encoded in the Pst DC3000 genome have been identified, the specific function for most of them remains to be elucidated. Among those effectors, the mitochondrial-localized T3E HopG1, suppresses plant defense responses and promotes the development of disease symptoms. Here, we show that HopG1 triggers necrotic cell death that enables the growth of adapted and non-adapted pathogens. We further showed that HopG1 interacts with the plant immunity-related protein AtNHR2B and that AtNHR2B attenuates HopG1- virulence functions. These results highlight the importance of HopG1 as a multi-faceted protein and uncover its interplay with AtNHR2B.