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Two CCAAT ‐box‐binding transcription factors redundantly regulate early steps of the legume‐rhizobia endosymbiosis
Author(s) -
Laloum Tom,
Baudin Maël,
Frances Lisa,
Lepage Agnes,
BillaultPenneteau Benjamin,
Cerri Marion R.,
Ariel Federico,
Jardinaud MarieFrançoise,
Gamas Pascal,
CarvalhoNiebel Fernanda,
Niebel Andreas
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12587
Subject(s) - medicago truncatula , biology , transactivation , rhizobia , microbiology and biotechnology , endosymbiosis , transcription factor , root nodule , nod factor , regulation of gene expression , sinorhizobium meliloti , gene , genetics , symbiosis , mutant , bacteria , plastid , chloroplast
Summary 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 N od 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 ( TF s) including CYCLOPS / IPD 3, NSP 1, NSP 2, ERN 1 and NIN . In this study, we bring convincing evidence that the M edicago truncatula CCAAT ‐box‐binding NF ‐ YA 1 TF , previously associated with later stages of rhizobial infection and nodule meristem formation is, together with its closest homolog NF ‐ YA 2 , also an essential positive regulator of the NF ‐signaling pathway. Here we show that NF ‐ YA 1 and NF ‐ YA 2 are both expressed in epidermal cells responding to NF s 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 ‐ YA 1 and NF ‐ YA 2 function, at least in part, via the direct activation of ERN 1 . We thus propose a model in which NF ‐ YA 1 and NF ‐ YA 2 appear as early symbiotic regulators acting downstream of DMI 3 and NIN and possibly within the same regulatory complexes as NSP 1/2 to directly activate the expression of ERN 1 .