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Special Issue "Molecular Research on Plant-Associated Nitrogen-Fixing Bacteria"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Plant Sciences".

Deadline for manuscript submissions: closed (30 September 2023) | Viewed by 1028

Special Issue Editor

Department of Biology, Portland State University, Portland, OR 97201, USA
Interests: interspecific interactions; chemical biology; insects, plants, and microbes

Special Issue Information

Dear Colleagues,

Modulating nitrogen-fixing microbial plant symbionts have a profound influence on ecosystem dynamics and global nitrogen cycles. Beyond the classical examples of legume–Rhizobia interactions, several other—and less studied—plant–microbe symbioses perform biological nitrogen fixation at large quantitative scales. For example, Frankia–alder symbioses rival legume–Rhizobia interactions in the amount of fixed atmospheric nitrogen. Nonetheless, we often lack knowledge around the identity, diversity, and physiology of plant-associated nitrogen-fixing microbes. Furthermore, recent work has shown that microorganisms inhabiting root nodules are more taxonomically and functionally diverse than previously thought and make complex multiplayer microbial communities. Effects on plant fitness, competitiveness, and stress tolerance of nodule communities has been predicted but only experimentally shown in isolated cases. To better understand these systems and their impact on the ecosystem, ample opportunities of studies in the fields of molecular and functional biology arise. We hope to capture an encompassing picture of these multilayer systems in this Special Issue of the International Journal of Molecular Sciences to better understand the diversity and functional role of these multiplayer systems and their impact on local and global ecosystems.

Prof. Dr. Stefanie Kautz
Guest Editor

Manuscript Submission Information

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  • plants
  • microbes
  • rhizobia
  • frankia
  • symbiosis
  • chemical biology
  • interspecific interactions
  • nitrogen fixation

Published Papers (1 paper)

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CRK12: A Key Player in Regulating the Phaseolus vulgaris-Rhizobium tropici Symbiotic Interaction
Int. J. Mol. Sci. 2023, 24(14), 11720; https://doi.org/10.3390/ijms241411720 - 21 Jul 2023
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Cysteine-rich receptor-like kinases (CRKs) are a type of receptor-like kinases (RLKs) that are important for pathogen resistance, extracellular reactive oxygen species (ROS) signaling, and programmed cell death in plants. In a previous study, we identified 46 CRK family members in the Phaseolus vulgaris [...] Read more.
Cysteine-rich receptor-like kinases (CRKs) are a type of receptor-like kinases (RLKs) that are important for pathogen resistance, extracellular reactive oxygen species (ROS) signaling, and programmed cell death in plants. In a previous study, we identified 46 CRK family members in the Phaseolus vulgaris genome and found that CRK12 was highly upregulated under root nodule symbiotic conditions. To better understand the role of CRK12 in the PhaseolusRhizobia symbiotic interaction, we functionally characterized this gene by overexpressing (CRK12-OE) and silencing (CRK12-RNAi) it in a P. vulgaris hairy root system. We found that the constitutive expression of CRK12 led to an increase in root hair length and the expression of root hair regulatory genes, while silencing the gene had the opposite effect. During symbiosis, CRK12-RNAi resulted in a significant reduction in nodule numbers, while CRK12-OE roots showed a dramatic increase in rhizobial infection threads and the number of nodules. Nodule cross sections revealed that silenced nodules had very few infected cells, while CRK12-OE nodules had enlarged infected cells, whose numbers had increased compared to controls. As expected, CRK12-RNAi negatively affected nitrogen fixation, while CRK12-OE nodules fixed 1.5 times more nitrogen than controls. Expression levels of genes involved in symbiosis and ROS signaling, as well as nitrogen export genes, supported the nodule phenotypes. Moreover, nodule senescence was prolonged in CRK12-overexpressing roots. Subcellular localization assays showed that the PvCRK12 protein localized to the plasma membrane, and the spatiotemporal expression patterns of the CRK12-promoter::GUS-GFP analysis revealed a symbiosis-specific expression of CRK12 during the early stages of rhizobial infection and in the development of nodules. Our findings suggest that CRK12, a membrane RLK, is a novel regulator of Phaseolus vulgaris-Rhizobium tropici symbiosis. Full article
(This article belongs to the Special Issue Molecular Research on Plant-Associated Nitrogen-Fixing Bacteria)
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