Understanding the mode of action of the symbiosis-specific NF-YA1 transcription factor in Medicago truncatula

RÍPODAS, CAROLINA; COURRÈGES-CLERCQ, JORDAN; LEPAGE, AGNES; NIEBEL, ANDREAS

Edimburgo

Simposio; 5th Agreenskills Annual Meeting 2018; 2018

Plants belonging to the legume family are able to interact symbiotically with nitrogen fixing bacteria named rhizobia, allowing these plants to grow in agricultural systems with low nitrogen inputs and thus to be important actors of sustainable agriculture. This symbiotic interaction leads to the formation of a new organ on the roots of the host plants, called nodule, inside which N2 is fixed for the benefit of the plant. Nodule development is specifically controlled by the nuclear factor Y (NF-Y) transcription factor (TF) NF-YA1. The heterotrimeric NF-Y complex is composed of the DNA-binding subunit NF-YA associated with two histone-like subunits NF-YB and NF-YC. Interestingly NF-Y is both a sequence specific TF, binding CCAAT boxes, but also shows nucleosome-like properties, promoting chromatin accessibility for other master TFs. Indeed, NF-YA1 of Medicago truncatula is rapidly, strongly and specifically expressed during nodule development, and knock-out mutant lines only form few small nodules that lack a functional meristem. The aim of my project is to thoroughly understand the mode of action of MtNF-YA1 transcription factor in nodule development. We are determining using ChIP-Seq the binding sites for this TF during nodule development. In addition, comparative transcriptome analysis using RNA-Seq in WT, mutant and overexpression backgrounds were performed. The combination of these approaches identified direct target genes of NF-Y complexes that we are currently studying. We will also identify and characterize new transcriptional regulators and proteins related to chromatin remodeling, able to interact and act jointly with NF-YA1 by isolation of nuclear proteins present in chromatin immunoprecipitated complexes coupled to mass spectrometry. Data generated in this project could help defining new strategies to promote better nodule development in legume crops during adverse conditions and to transfer nodule development into non-nitrogen-fixing crops thereby contributing to the ongoing worldwide effort to increase biological nitrogen fixation in agriculture.