A phylogenetically conserved group of NF-Y transcription factors interact to control nodulation in legumes

MAËL BAUDIN; TOM LALOUM; AGNES LEPAGE; CAROLINA RIPODAS; FEDERICO ARIEL ; LISA FRANCES; MARTIN CRESPI; PASCAL C GAMAS; FLAVIO ANTONIO BLANCO ; MARÍA EUGENIA ZANETTI; FERNANDA DE CARVALHO-NIEBEL; ANDREAS NIEBEL

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Lugar: Rockville; Año: 2015

0032-0889

The endosymbiotic association between legumes and soil bacteria called rhizobia leads to the formation of a new root-derived organ called the nodule in which differentiated bacteria convert atmospheric nitrogen into a form that can be assimilated by the host plant. Successful root infection by rhizobia and nodule organogenesis require the activation of symbiotic genes that are controlled by a set of early transcription factors (TFs). We recently identified MtNF-YA1 and MtNF-YA2 as two Medicago truncatula TFs playing a central role during key steps of the Sinorhizobium meliloti-M. truncatula symbiotic interaction. NF-YA TFs interact with NF-YB and NF-YC subunits to regulate target genes containing the CCAAT-box sequence motif. In this study, using a yeast two hybrid screen approach, we identified the NF-YB and NF-YC subunits able to specifically interact with MtNF-YA1 and A2. We further demonstrated in yeast and in planta by co-immunoprecipitation and BiFC that these three NF-YA, B and C subunits can interact and form a stable NF-Y heterotrimeric complex. Reverse genetics and ChIP-PCR approaches revealed the importance of these newly identified NF-YB and NF-YC subunits to rhizobial symbiosis and to the regulation of a direct target gene of NF-YA1&2. Finally, we also verified that a similar trimer is formed in planta by the Phaseolus vulgaris NF-Y subunits, revealing the existence of evolutionary conserved NF-Y protein complexes to control nodulation in leguminous plants. This sheds some light on the process whereby an ancient heterotrimeric transcription factor mainly controlling cell division in animals has acquired specialized functions in plants.