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ORIGINAL RESEARCH article

Front. Plant Sci.
Sec. Plant Symbiotic Interactions
Volume 15 - 2024 | doi: 10.3389/fpls.2024.1468812
This article is part of the Research Topic Highlights of iMMM2023 - International Molecular Mycorrhiza Meeting View all 7 articles

Ectopic expression of the GRAS-type transcriptional regulator NSP2 in Parasponia triggers contrasting effects on symbioses

Provisionally accepted
Sultan Alhusayni Sultan Alhusayni 1,2Nick Kersten Nick Kersten 1Rik Huisman Rik Huisman 1Rene Geurts Rene Geurts 1*Joël Klein Joël Klein 1*
  • 1 Wageningen University and Research, Wageningen, Netherlands
  • 2 King Faisal University, Al-Ahsa, Eastern Province, Saudi Arabia

The final, formatted version of the article will be published soon.

    Plants strictly control root endosymbioses with nutrient-scavenging arbuscular endomycorrhizal fungi or nodule inducing diazotrophic bacteria. The GRAS-type transcriptional regulator NODULATION SIGNALING PATHWAY 2 (NSP2) is a conserved hub in this process. The NSP2-regulated transcriptional network is instrumental in balancing nutrient homeostasis with symbiotic interactions. NSP2 activity is modulated post-transcriptionally by a specific microRNA. Overriding this control mechanism by ectopic expression of a miRNA-resistant NSP2 transgene enhances the symbiotic permissiveness to arbuscular endomycorrhizal fungi. Such engineered plants may possess enhanced capacities for nutrient uptake. However, the trade-off of this strategy on plant development or other symbiotic interactions, like nodulation, is yet to be fully understood. We used the nodulating Cannabaceae species Parasponia andersonii as an experimental system to study the effect of ectopic NSP2 expression. Parasponia and legumes (Fabaceae) diverged 100 million years ago, providing a unique comparative system to dissect the nodulation trait. Six independent transgenic Parasponia lines were generated that differed in the level of NSP2 expression in the root from 6 to 95-fold higher when compared to the empty vector control plants. Analysis of these plants revealed a positive correlation between mycorrhization and the NSP2 expression level, as well as with the expression of the symbiosis transcription factor CYCLOPS and the rate-limiting enzyme in the carotenoid biosynthetic pathway PHYTOENE SYNTHASE1 (PSY1). Yet ectopic expression of NSP2 affected plant architecture and root nodule organogenesis. This indicates a significant trade-off when leveraging NSP2 over-expression to enhance endomycorrhization.

    Keywords: arbuscular mycorrhiza, nodulation, Parasponia, NSP2, Cyclops, Phytoene synthase, Carotenoids, strigolactones Rhizobium-induced Parasponia nodules are Font: Italic Supplemental Figure S3A relative to control (* P< 0.05

    Received: 22 Jul 2024; Accepted: 03 Oct 2024.

    Copyright: © 2024 Alhusayni, Kersten, Huisman, Geurts and Klein. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence:
    Rene Geurts, Wageningen University and Research, Wageningen, 6708 PB, Netherlands
    Joël Klein, Wageningen University and Research, Wageningen, 6708 PB, Netherlands

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