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Arbuscular-Mycorrhizal Symbiosis in Medicago Regulated by the Transcription Factor MtbHLHm1;1 and the Ammonium Facilitator Protein MtAMF1;3

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posted on 2023-10-27, 02:45 authored by Evgenia Ovchinnikova, David Chiasson, Zhengyu Wen, Yue Wu, Hero Tahaei, Penelope SmithPenelope Smith, Francine Perrine-Walker, Brent N Kaiser
Root systems of most land plants are colonised by arbuscular mycorrhiza fungi. The symbiosis supports nutrient acquisition strategies predominantly associated with plant access to inorganic phosphate. The nutrient acquisition is enhanced through an extensive network of external fungal hyphae that extends out into the soil, together with the development of fungal structures forming specialised interfaces with root cortical cells. Orthologs of the bHLHm1;1 transcription factor, previously described in soybean nodules (GmbHLHm1) and linked to the ammonium facilitator protein GmAMF1;3, have been identified in Medicago (Medicago truncatula) roots colonised by AM fungi. Expression studies indicate that transcripts of both genes are also present in arbuscular containing root cortical cells and that the MtbHLHm1;1 shows affinity to the promoter of MtAMF1;3. Both genes are induced by AM colonisation. Loss of Mtbhlhm1;1 expression disrupts AM arbuscule abundance and the expression of the ammonium transporter MtAMF1;3. Disruption of Mtamf1;3 expression reduces both AM colonisation and arbuscule development. The respective activities of MtbHLHm1;1 and MtAMF1;3 highlight the conservation of putative ammonium regulators supporting both the rhizobial and AM fungal symbiosis in legumes.


This research was funded by an Australian Research Council Discovery Grant awarded to B.N. Kaiser, P. Smith, M. Unkovich (DP150102264) and the ARC ITRH—Legumes for Sustainable Agriculture (IH140100013) awarded to B.N.K and P. Smith.


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International Journal of Molecular Sciences





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Multidisciplinary Digital Publishing Institute



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© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (