March
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.
April
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).
May
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.
