The CEP peptide-CRA2 receptor module promotes arbuscular mycorrhizal symbiosis.

C-terminally encoded peptides (CEPs) are small secreted signaling peptides that promote nitrogen-fixing root nodulation symbiosis in legumes, depending on soil mineral nitrogen availability. In Medicago truncatula, their action is mediated by the leucine-rich repeat receptor-like protein kinase COMPACT ROOT ARCHITECTURE 2 (CRA2). Like most land plants, under inorganic phosphate limitation, M.

The Compact Root Architecture 2 systemic pathway is required for the repression of cytokinins and miR399 accumulation in Medicago truncatula N-limited plants.

Legume plants can acquire mineral nitrogen (N) either through their roots or via a symbiotic interaction with N-fixing rhizobia bacteria housed in root nodules. To identify shoot-to-root systemic signals acting in Medicago truncatula plants at N deficit or N satiety, plants were grown in a split-root experimental design in which either high or low N was provided to half of the root system, allowing the analysis of systemic pathways independently of any local N response. Among the plant hormone families analyzed, the cytokinin trans-zeatin accumulated in plants at N satiety.

Localized osmotic stress activates systemic responses to N limitation in symbiotic plants.

In mature symbiotic root nodules, differentiated rhizobia fix atmospheric dinitrogen and provide ammonium to fulfill the plant nitrogen (N) demand. The plant enables this process by providing photosynthates to the nodules. The symbiosis is adjusted to the whole plant N demand thanks to systemic N signaling controlling nodule development.

Rhizobium symbiotic efficiency meets CEP signaling peptides.

C-terminally encoded peptides (CEP) signaling peptides are drivers of systemic pathways regulating nitrogen (N) acquisition in different plants, from Arabidopsis to legumes, depending on mineral N availability (e.g. nitrate) and on the whole plant N demand.

HSFA1a modulates plant heat stress responses and alters the 3D chromatin organization of enhancer-promoter interactions.

The complex and dynamic three-dimensional organization of chromatin within the nucleus makes understanding the control of gene expression challenging, but also opens up possible ways to epigenetically modulate gene expression. Because plants are sessile, they evolved sophisticated ways to rapidly modulate gene expression in response to environmental stress, that are thought to be coordinated by changes in chromatin conformation to mediate specific cellular and physiological responses. However, to what extent and how stress induces dynamic changes in chromatin reorganization remains poorly understood.

The Medicago SymCEP7 hormone increases nodule number via shoots without compromising lateral root number.

Legumes acquire soil nutrients through nitrogen-fixing root nodules and lateral roots. To balance the costs and benefits of nodulation, legumes negatively control root nodule number by autoregulatory and hormonal pathways. How legumes simultaneously coordinate root nodule and lateral root development to procure nutrients remains poorly understood.

Cell-specific pathways recruited for symbiotic nodulation in the Medicago truncatula legume.

Medicago truncatula is a model legume species that has been studied for decades to understand the symbiotic relationship between legumes and soil bacteria collectively named rhizobia. This symbiosis called nodulation is initiated in roots with the infection of root hair cells by the bacteria, as well as the initiation of nodule primordia from root cortical, endodermal, and pericycle cells, leading to the development of a new root organ, the nodule, where bacteria fix and assimilate the atmospheric dinitrogen for the benefit of the plant. Here, we report the isolation and use of the nuclei from mock and rhizobia-inoculated roots for the single nuclei RNA-seq (sNucRNA-seq) profiling to gain a deeper understanding of early responses to rhizobial infection in Medicago roots.

A dual legume-rhizobium transcriptome of symbiotic nodule senescence reveals coordinated plant and bacterial responses.

Senescence determines plant organ lifespan depending on aging and environmental cues. During the endosymbiotic interaction with rhizobia, legume plants develop a specific organ, the root nodule, which houses nitrogen (N)-fixing bacteria. Unlike earlier processes of the legume-rhizobium interaction (nodule formation, N fixation), mechanisms controlling nodule senescence remain poorly understood.

Nitrate-induced CLE35 signaling peptides inhibit nodulation through the SUNN receptor and miR2111 repression.

Legume plants form nitrogen (N)-fixing symbiotic nodules when mineral N is limiting in soils. As N fixation is energetically costly compared to mineral N acquisition, these N sources, and in particular nitrate, inhibit nodule formation and N fixation. Here, in the model legume Medicago truncatula, we characterized a CLAVATA3-like (CLE) signaling peptide, MtCLE35, the expression of which is upregulated locally by high-N environments and relies on the Nodule Inception-Like Protein (NLP) MtNLP1.

Nitrogen Systemic Signaling: From Symbiotic Nodulation to Root Acquisition.

Plant nutrient acquisition is tightly regulated by resource availability and metabolic needs, implying the existence of communication between roots and shoots to ensure their integration at the whole-plant level. Here, we focus on systemic signaling pathways controlling nitrogen (N) nutrition, achieved both by the root import of mineral N and, in legume plants, through atmospheric N fixation by symbiotic bacteria inside dedicated root nodules. We explore features conserved between systemic pathways repressing or enhancing symbiotic N fixation and the regulation of mineral N acquisition by roots, as well as their integration with other environmental factors, such as phosphate, light, and CO availability.

A CEP Peptide Receptor-Like Kinase Regulates Auxin Biosynthesis and Ethylene Signaling to Coordinate Root Growth and Symbiotic Nodulation in .

Because of the large amount of energy consumed during symbiotic nitrogen fixation, legumes must balance growth and symbiotic nodulation. Both lateral roots and nodules form on the root system, and the developmental coordination of these organs under conditions of reduced nitrogen (N) availability remains elusive. We show that the COMPACT ROOT ARCHITECTURE2 (MtCRA2) receptor-like kinase is essential to promote the initiation of early symbiotic nodulation and to inhibit root growth in response to low N.

A linkage disequilibrium-based statistical test for Genome-Wide Epistatic Selection Scans in structured populations.

The quest for signatures of selection using single nucleotide polymorphism (SNP) data has proven efficient to uncover genes involved in conserved and/or adaptive molecular functions, but none of the statistical methods were designed to identify interacting alleles as targets of selective processes. Here, we propose a statistical test aimed at detecting epistatic selection, based on a linkage disequilibrium (LD) measure accounting for population structure and heterogeneous relatedness between individuals. SNP-based ([Formula: see text]) and window-based ([Formula: see text]) statistics fit a Student distribution, allowing to test the significance of correlation coefficients.

A CEP Peptide Receptor-like Kinase Regulates Auxin Biosynthesis and Ethylene Signaling to Coordinate Root Growth and Symbiotic Nodulation in Medicago truncatula.

Because of the high energy consumed during symbiotic nitrogen fixation, legumes must balance growth and symbiotic nodulation. Both lateral roots and nodules form on the root system and the developmental coordination of these organs according to reduced nitrogen (N) availability remains elusive. We show that the Compact Root Architecture 2 (MtCRA2) receptor-like kinase is essential to promote the initiation of early symbiotic nodulation and to inhibit root growth in response to low-N.

The NIN transcription factor coordinates CEP and CLE signaling peptides that regulate nodulation antagonistically.

Legumes tightly regulate nodule number to balance the cost of supporting symbiotic rhizobia with the benefits of nitrogen fixation. C-terminally Encoded Peptides (CEPs) and CLAVATA3-like (CLE) peptides positively and negatively regulate nodulation, respectively, through independent systemic pathways, but how these regulations are coordinated remains unknown. Here, we show that rhizobia, Nod Factors, and cytokinins induce a symbiosis-specific CEP gene, MtCEP7, which positively regulates rhizobial infection.

A Cytokinin Signaling Type-B Response Regulator Transcription Factor Acting in Early Nodulation.

Nitrogen-fixing root nodulation in legumes challenged with nitrogen-limiting conditions requires infection of the root hairs by soil symbiotic bacteria, collectively referred to as rhizobia, and the initiation of cell divisions in the root cortex. Cytokinin hormones are critical for early nodulation to coordinate root nodule organogenesis and the progression of bacterial infections. Cytokinin signaling involves regulation of the expression of cytokinin primary response genes by type-B response regulator (RRB) transcription factors.

Compact Root Architecture 2 Promotes Root Competence for Nodulation through the miR2111 Systemic Effector.

Nitrogen-deprived legume plants form new root organs, the nodules, following a symbiosis with nitrogen-fixing rhizobial bacteria [1]. Because this interaction is beneficial for the plant but has a high energetic cost, nodulation is tightly controlled by host plants through systemic pathways (acting at long distance) to promote or limit rhizobial infections and nodulation depending on earlier infections and on nitrogen availability [2]. In the Medicago truncatula model legume, CLE12 (Clavata3/Embryo surrounding region 12) and CLE13 signaling peptides produced in nodulated roots act in shoots through the SUNN (Super Numeric Nodule) receptor to negatively regulate nodulation and therefore autoregulate nodule number [3-5].

CEP receptor signalling controls root system architecture in Arabidopsis and Medicago.

Root system architecture (RSA) influences the effectiveness of resources acquisition from soils but the genetic networks that control RSA remain largely unclear. We used rhizoboxes, X-ray computed tomography, grafting, auxin transport measurements and hormone quantification to demonstrate that Arabidopsis and Medicago CEP (C-TERMINALLY ENCODED PEPTIDE)-CEP RECEPTOR signalling controls RSA, the gravitropic set-point angle (GSA) of lateral roots (LRs), auxin levels and auxin transport. We showed that soil-grown Arabidopsis and Medicago CEP receptor mutants have a narrower RSA, which results from a steeper LR GSA.

Diversification of cytokinin phosphotransfer signaling genes in Medicago truncatula and other legume genomes.

Background: Legumes can establish on nitrogen-deprived soils a symbiotic interaction with Rhizobia bacteria, leading to the formation of nitrogen-fixing root nodules. Cytokinin phytohormones are critical for triggering root cortical cell divisions at the onset of nodule initiation. Cytokinin signaling is based on a Two-Component System (TCS) phosphorelay cascade, involving successively Cytokinin-binding Histidine Kinase receptors, phosphorelay proteins shuttling between the cytoplasm and the nucleus, and Type-B Response Regulator (RRB) transcription factors activating the expression of cytokinin primary response genes.

Gibberellins negatively regulate the development of Medicago truncatula root system.

The root system displays a remarkable plasticity that enables plants to adapt to changing environmental conditions. This plasticity is tightly linked to the activity of root apical meristems (RAMs) and to the formation of lateral roots, both controlled by related hormonal crosstalks. In Arabidopsis thaliana, gibberellins (GAs) were shown to positively control RAM growth and the formation of lateral roots.

Independent Regulation of Symbiotic Nodulation by the SUNN Negative and CRA2 Positive Systemic Pathways.

Plant systemic signaling pathways allow the integration and coordination of shoot and root organ metabolism and development at the whole-plant level depending on nutrient availability. In legumes, two systemic pathways have been reported in the model to regulate root nitrogen-fixing symbiotic nodulation. Both pathways involve leucine-rich repeat receptor-like kinases acting in shoots and proposed to perceive signaling peptides produced in roots depending on soil nutrient availability.

Unraveling new molecular players involved in the autoregulation of nodulation in Medicago truncatula.

The number of legume root nodules resulting from a symbiosis with rhizobia is tightly controlled by the plant. Certain members of the CLAVATA3/Embryo Surrounding Region (CLE) peptide family, specifically MtCLE12 and MtCLE13 in Medicago truncatula, act in the systemic autoregulation of nodulation (AON) pathway that negatively regulates the number of nodules. Little is known about the molecular pathways that operate downstream of the AON-related CLE peptides.

Whole-genome landscape of Medicago truncatula symbiotic genes.

Advances in deciphering the functional architecture of eukaryotic genomes have been facilitated by recent breakthroughs in sequencing technologies, enabling a more comprehensive representation of genes and repeat elements in genome sequence assemblies, as well as more sensitive and tissue-specific analyses of gene expression. Here we show that PacBio sequencing has led to a substantially improved genome assembly of Medicago truncatula A17, a legume model species notable for endosymbiosis studies, and has enabled the identification of genome rearrangements between genotypes at a near-base-pair resolution. Annotation of the new M.