Two AMP-Binding Domain Proteins from Rhizophagus irregularis Involved in Import of Exogenous Fatty Acids
M. Brands and P. Dörmann
Since it is unknown how arbuscular mycorrhizal fungi (AMF) take up host-derived fatty acids, which they need for nutrients, Mathias Brands and Peter Dörmann describe the characterization of two AMP-binding domain protein genes from Rhizophagus irregularis with sequence similarity to Saccharomyces cerevisiae fatty acid transporter 1 (FAT1). Their results suggest the two proteins might be involved in fatty acid import into the fungal arbuscules in colonized roots.
Recognition of Microbe- and Damage-Associated Molecular Patterns by Leucine-Rich Repeat Pattern Recognition Receptor Kinases Confers Salt Tolerance in Plants
E. P.-I. Loo, Y. Tajima, K. Yamada, S. Kido, T. Hirase, H. Ariga, T. Fujiwara, K. Tanaka, T. Taji, I. E. Somssich, J. E. Parker, and Y. Saijo
Eliza Loo et al. find that activation of MAMP/DAMP signaling by a broad array of signals primes the plant to tolerate subsequent salt stress, demonstrating integration of abiotic and biotic signals via a conserved BAK1/BIK1 signaling pathway. This example of a biotic signaling promoting subsequent tolerance of an abiotic stress reveals the complexity of interactions of plants with their living and nonliving environment and may open new avenues to promote plant health in the field.
Involvement of Arabidopsis Acyl Carrier Protein 1 in PAMP-Triggered Immunity
Z. Zhao, J. Fan, P. Yang, Z. Wang, S. Obol Opiyo, D. Mackey, and Y. Xia
Acyl carrier proteins (ACPs) are central components of fatty acid (FA) synthesis. Zhenzhen Zhao et al. show that ACP1 influences plant immunity by maintaining the balance of defense hormones jasmonic acid and salicylic acid, providing a direct link between FA and lipid biosynthesis to plant immune responses. This opens up the possibility of engineering disease-resistant plant varieties by modifying the expression levels of ACP1 in economically important crops.
Two Related Picks from the MPMI Editors: We've studied rhizobia and legumes for a long time, and here we highlight two Editor's Picks that are beginning to address a whole new field: positive effects on nonhost plant growth and development by rhizobia. Both the Mercedes Schroeder et al. and the Casandra Hernández-Reyes et al. papers identify specific mechanisms by which symbiotic rhizobium bacteria promote the root growth of a nonhost, Arabidopsis, altering root architecture via auxin transport (Schroeder et al.) and modulating cell division and cell elongation via NLP-mediated nitrate signaling (Hernández-Reyes et al.).
Bradyrhizobium japonicum IRAT FA3 Alters Arabidopsis thaliana Root Architecture via Regulation of Auxin Efflux Transporters PIN2, PIN3, PIN7, and ABCB19
Mercedes M. Schroeder, Melissa Y. Gomez, Nathan McLain, and Emma W. Gachomo
Plant root development changes in response to beneficial rhizobacteria. This MPMI paper by Schroeder et al. shows B. japonicum's influence on host transcriptional reprogramming during their beneficial interaction. Through bacterial association with knockout lines, plant auxin efflux transporters were identified as critical to developing the B. japonicum-modified root architecture.
NIN-Like Proteins: Interesting Players in Rhizobia-Induced Nitrate Signaling Response During Interaction with Non-Legume Host Arabidopsis thaliana
Casandra Hernández-Reyes, Elisabeth Lichtenberg, Jean Keller, Pierre-Marc Delaux, Thomas Ott, and Sebastian T. Schenk
As an essential macronutrient, nitrogen plays an important role in plant development and plant–microbe symbioses, including legume–rhizobia interactions. Hernández-Reyes et al. demonstrate that a nitrate-related NLP signaling pathway in Arabidopsis regulates rhizobium-induced lateral root growth and increased root hair length and density. The involvement of two NLP transcription factors in mediating this response and their similarity to known legume NLPs involved in nodule symbiosis suggests the response to rhizobia is a trait shared within that protein clade.
Analysis of Outer Membrane Vesicles Indicates That Glycerophospholipid Metabolism Contributes to Early Symbiosis Between Sinorhizobium fredii HH103 and Soybean
Dongzhi Li, Ziqi Li, Jing Wu, Zhide Tang, Fuli Xie, Dasong Chen, Hui Lin, and Youguo Li
Gram-negative bacteria can produce outer membrane vesicles (OMVs), and most functional studies of OMVs have been focused on mammalian-bacterial interactions. Research on the OMVs of rhizobia is limited. In this work, Dhongzhi Li et al. isolated and purified OMVs from Sinorhizobium fredii HH103 under free-living conditions that were set as control (C-OMVs) and symbiosis-mimicking conditions that were induced by genistein (G-OMVs).
Synergistic Effects of a Root-Endophytic Trichoderma Fungus and Bacillus on Early Root Colonization and Defense Activation Against Verticillium longisporum in Rapeseed
Fatema Binte Hafiz, Narges Moradtalab, Simon Goertz, Steffen Rietz, Kristin Dietel, Wilfried Rozhon, Klaus Humbeck, Joerg Geistlinger, Günter Neumann, and Ingo Schellenberg
Rhizosphere-competent microbes often interact with plant roots and exhibit beneficial effects on plant performance. Numerous bacterial and fungal isolates are able to prime host plants for fast adaptive responses against pathogen attacks. The combined action of fungi and bacteria may lead to synergisms exceeding the effects of single strains. This study by Fatema Binte Hafiz et al. offers a perspective for the development of alternative and sustainable approaches to enhance the tolerance of rapeseed cultures against fungal infections.
Increasingly, new evidence is revealing variability in the epitope regions of bacterial flagellin, including in regions harboring the microbe-associated molecular patterns flg22 and flgII-28 that are recognized by the pattern recognition receptors. Learn more from Maria Malvino and colleagues in their paper "Influence of Flagellin Polymorphisms, Gene Regulation, and Responsive Memory on the Motility of Xanthomonas Species That Cause Bacterial Spot Disease of Solanaceous Plants."
The Natural Antisense Transcript
DONE40 Derived from the lncRNA
ENOD40 Locus Interacts with SET Domain Protein ASHR3 during Inception of Symbiosis in
Pritha Ganguly, Dipan Roy, Troyee Das, Anindya Kundu, Fabienne Cartieaux, Zhumur Ghosh, and Maitrayee DasGupta
The long noncoding RNA
ENOD40 is required for cortical cell division during root nodule symbiosis (RNS) of legumes, although it is not essential for actinorhizal RNS.
Ganguly et al. set out to understand whether
ENOD40 is required for aeschynomenoid nodule formation in
AhENOD40 expresses from chromosomes 5 (AhENOD40-1) and 15 (AhENOD40-2) during symbiosis, and RNA interference by these transcripts drastically affects nodulation, indicating the importance of
Metatranscriptomic Comparison of Endophytic and Pathogenic Fusarium–Arabidopsis Interactions Reveals Plant Transcriptional Plasticity
Li Guo, Houlin Yu, Bo Wang, Kathryn Vescio, Gregory A. DeIulio, He Yang, Andrew Berg, Lili Zhang, Véronique Edel-Hermann, Christian Steinberg, H. Corby Kistler, and Li-Jun Ma
Two strains of the fungus Fusarium oxysporum (Fo) share a core genome, but one is a beneficial endophyte while the other is a detrimental pathogen causing wilt and death. Guo et al. tried to tease apart why these two strains cause such opposite reactions, and more generally how plants respond differently to useful and harmful microbes, by exploring the interaction of these two strains with the model plant Arabidopsis.
Chitin Deacetylases Are Required for
Epichloë festucae Endophytic Cell Wall Remodeling during Establishment of a Mutualistic Symbiotic Interaction with
Nazanin Noorifar, Matthew S. Savoian, Arvina Ram, Yonathan Lukito, Berit Hassing, Tobias W. Weikert, Bruno M. Moerschbacher, and Barry Scott
A diverse set of microbes survives and thrives inside plants as endophytes, but we have little mechanistic understanding of these intimate associations. In their study,
Noorifar et al. show the way in which an
Epichloë endophyte remodels its cell wall, converting chitin to chitosan, to avoid detection by host defenses. Deletion mutants reveal an important role for chitin deacetylases in hyphal growth inside the plant.
Computational Structural Genomics Unravels Common Folds and Novel Families in the Secretome of Fungal Phytopathogen
Kyungyong Seong and Ksenia V. Krasileva
Recent breakthroughs in protein structure modeling demonstrate the ability to predict protein folds without depending on homologous templates. In their study,
Krasileva employed structure prediction methods on the secretome of the destructive fungal pathogen
Magnaporthe oryzae. Out of 1,854 secreted proteins, they predicted the folds of 1,295 proteins (70%).
Many plant-encoded E3 ligases are known to be involved in plant defense. Ramu et al. report a novel role of E3 ligase SALT- AND DROUGHT-INDUCED RING FINGER1 (SDIR1) in plant immunity. Their research suggests that SDIR1 is a susceptibility factor and its activation or overexpression enhances disease caused by P. syringae pv. tomato DC3000 in Arabidopsis.
Puccinia striiformis f. sp. tritici is the causal agent of wheat stripe rust that causes severe yield losses all over the world. Zhao et al. represent the first analysis of the P. striiformis f. sp. tritici transcriptome in barberry and contribute to a better understanding of the evolutionary processes and strategies of different types of rust spores during the infection process on different hosts.
Gao and colleagues use alanine scanning of the Tobacco necrosis virus-A coat
protein to identify 3 amino acid residues that differentially affect movement
of the virus through the plant in tobacco and soybean, as well as identifying
host specific interactions of the HSP70 protein Hsc70-2 with the coat protein
to mediate systemic infection.
Clark and colleagues investigate the role of the Liberibacter effector SDE1, finding that it promotes colonization by Liberibacter, the causative agent of citrus greening disease, or huanglongbing, likely by inducing premature senescence responses in leaves.
Wheat stem rust, a previously well-controlled disease, has reemerged as a major threat to wheat, with major outbreaks in Africa, Europe, and central Asia. The stem rust resistance gene Sr22 encodes a nucleotide-binding and leucine-rich repeat receptor, which confers resistance to the highly virulent African stem rust isolate, Ug99. Hatta et al. show that the Sr22 gene is conserved among grasses in the Triticeae and Poeae lineages.