1. Two CCAAT-box-binding transcription factors redundantly regulate early steps of the legume-rhizobia endosymbiosis.
- Author
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Laloum, Tom, Baudin, Maël, Frances, Lisa, Lepage, Agnes, Billault-Penneteau, Benjamin, Cerri, Marion R., Ariel, Federico, Jardinaud, Marie-Françoise, Gamas, Pascal, Carvalho-Niebel, Fernanda, and Niebel, Andreas
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TRANSCRIPTION factors , *GENETIC regulation , *LEGUME genetics , *RHIZOBIACEAE , *ENDOSYMBIOSIS , *NITROGEN fixation - 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 Ch IP- 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. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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