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Two CCAAT-box-binding transcription factors redundantly regulate early steps of the legume-rhizobia endosymbiosis

Abstract : During endosymbiotic interactions between legume plants and nitrogen-fixing rhizobia, successful root infection by bacteria and nodule organogenesis requires the perception and transduction of bacterial lipo-chitooligosaccharidic signal called Nod factor (NF). NF perception in legume roots leads to the activation of an early signaling pathway and of a set of symbiotic genes which is controlled by specific early transcription factors (TFs) including CYCLOPS/IPD3, NSP1, NSP2, ERN1 and NIN. In this study, we bring convincing evidence that the Medicago truncatula CCAAT-box-binding NF-YA1 TF, previously associated with later stages of rhizobial infection and nodule meristem formation is, together with its closest homolog NF-YA2, also an essential positive regulator of the NF-signaling pathway. Here we show that NF-YA1 and NF-YA2 are both expressed in epidermal cells responding to NFs and their knock-down by reverse genetic approaches severely affects the NF-induced expression of symbiotic genes and rhizobial infection. Further over-expression, transactivation and ChIP-PCR approaches indicate that NF-YA1 and NF-YA2 function, at least in part, via the direct activation of ERN1. We thus propose a model in which NF-YA1 and NF-YA2 appear as early symbiotic regulators acting downstream of DMI3 and NIN and possibly within the same regulatory complexes as NSP1/2 to directly activate the expression of ERN1.
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https://hal-cnrs.archives-ouvertes.fr/hal-03082944
Contributor : Fernanda de Carvalho-Niebel <>
Submitted on : Friday, December 18, 2020 - 6:24:19 PM
Last modification on : Wednesday, January 13, 2021 - 3:38:16 AM

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Tom Laloum, Maël Baudin, Lisa Frances, Agnes Lepage, Benjamin Billault-Penneteau, et al.. Two CCAAT-box-binding transcription factors redundantly regulate early steps of the legume-rhizobia endosymbiosis. Plant Journal, Wiley, 2014, 79 (5), pp.757-768. ⟨10.1111/tpj.12587⟩. ⟨hal-03082944⟩

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