Biology subjects

Courty, P.-E.

Publications and source records attributed to Courty, P.-E..

5 recordsLinked to original sources

bioRxiv2024

Strigolactone receptor DAD2 promotes lateral root formation in Petunia hybrida

Strigolactone regulates various aspects of plant development and interactions with beneficial microbes. While the role of SL in shoot development is highly conserved between monocots and dicots, its role in root system architecture is controversial and context-dependent, although most of the SL appears to be produced there. A central parameter in plant fitness is root-to-shoot ratio, which is determined by growth and branching activity of both, the root as well as the shoot. We used previously characterized mutants defective in SL biosynthesis and sensing to test the role of SL in root growth and branching. Here, we show that a mutant defective in the petunia strigolactone receptor (dad2) exhibits defects in root meristem activity and root branching. Notably, this phenotype is not observed in the SL biosynthetic mutant dad1, suggesting that DAD2 may perceive a strigolactone analogue that is produced in a DAD1-independently fashion. DAD2 is induced in cortex cells adjacent to lateral root primordia, where it allows them to penetrate the cortex and to grow out of the main root. We propose a model by which inducible SL perception in cells adjacent to LRPs promotes auxin-induced cell wall remodeling in the cortex to allow passage of lateral roots. 1-sentence summaryLateral roots are initiated inside the main root, hence, they have to penetrate several cell layers to grow out. We propose that strigolactone cooperates with auxin to mediate lateral root emergence.

plant biology↗

bioRxiv2023

Maize (Zea mays L.) interaction with the arbuscular mycorrhizal fungus Rhizophagus irregularis allows mitigation of nitrogen deficiency stress: physiological and molecular characterization

Maize is currently the most productive cereal crop in the world (www.faostat.org). Maize can form a symbiotic relationship with the Arbuscular Mycorrhizal Fungus (AMF), Rhizophagus irregularis. In this relationship, the fungus provides the plant with additional water and mineral nutrients, while the plant supplies carbon compounds to the fungus. Little is known about the N metabolism disruption during symbiosis in both partners. To address this issue, two genetically distant maize lines were studied in terms of physiological and molecular responses to AMF inoculation by dual RNA-seq, metabolomics and phenotyping. Interestingly, the beneficial effects of the AMF were observed mainly under conditions of limited N fertilization. Under such conditions, the AMF helped maintain plant biomass production. The availability of nitrogen was found to be a crucial factor influencing all the traits studied showing that the level of N supply plays a pivotal role in determining how maize plants interact with the AMF. Despite the two maize lines showing different transcriptomic and metabolomic responses to R. irregularis, their agro-physiological traits remained similar. Both the plant and fungal transcriptomes were more significantly influenced by the level of N nutrition rather than the specific maize genotype. This suggests that N availability has a more profound impact on gene expression in both organisms than the genetic makeup of the maize plant. To understand the metabolic implications of this symbiotic relationship, we integrated transcriptomic data into our recently built multi-organ Genome-scale metabolic model (GSM) called iZMA6517. Remarkably, this modelling approach was supported by metabolomics profiling, in particular increased leaf pyrimidine levels in response to AMF inoculation under limiting N supply. Consistently, fungal genes involved in pyrimidine de novo synthesis and salvage were found to be expressed in symbiotic roots. Our work highlights nucleotide and ureides metabolism as previously unrecognized factors contributing to the symbiotic N nutrition facilitated by R. irregularis, thereby enhancing maize growth. This study demonstrates the effectiveness of integrating multi-omics approaches with mathematical modelling to uncover novel metabolic mechanisms associated with AM symbiosis, without a priori.

plant biology↗

bioRxiv2022

Arbuscular mycorrhizal fungus Rhizophagus irregularis expresses an outwardly Shaker-like channel involved in potassium nutrition of rice (Oryza sativa L.)

Potassium (K+) plays crucial roles in many physiological, molecular and cellular processes in plants. Direct uptake of this nutrient by root cells has been extensively investigated, however, indirect uptake of K+ mediated by the interactions of the roots with fungi in the frame of a mutualistic symbiosis, also called mycorrhizal nutrient uptake pathway, is much less known. We identified an ion channel in the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis. This channel exhibits the canonical features of Shaker-like channel shared in other living kingdoms and is named RiSKC3. Transcriptionally expressed in hyphae and in arbuscules of colonized rice roots, RiSKC3 has been shown to be located in the plasma membrane. Voltage-clamp functional characterization in Xenopus oocytes revealed that RiSKC3 is endowed with outwardly-rectifying voltage-gated activity with a high selectivity for potassium over sodium ions. RiSKC3 may have a role in the AM K+ pathway for rice nutrition in normal and salt stress conditions. The current working model proposes that K+ ions taken up by peripheral hyphae of R. irregularis are secreted towards the host root into periarbuscular space by RiSKC3. Significance StatementArbuscular mycorhizal fungus Rhizophagus irregularis expresses a Shaker-like channel, located in the plasma membrane, endowed with a strictly outwardly-rectifying voltage-gated activity with a high selectivity for potassium over sodium ions. The current working model proposes that K+ ions taken up by peripheral hyphae of R. irregularis are secreted towards the host root into periarbuscular space by this Shaker-like channel.

plant biology↗

bioRxiv2022

The giant diploid faba genome unlocks variation in a global protein crop

Increasing the proportion of locally produced plant protein in currently meat-rich diets could substantially reduce greenhouse gas emission and loss of biodiversity. However, plant protein production is hampered by the lack of a cool-season legume equivalent to soybean in agronomic value. Faba bean (Vicia faba L.) has a high yield potential and is well-suited for cultivation in temperate regions, but genomic resources are scarce. Here, we report a high-quality chromosome-scale assembly of the faba bean genome and show that it has grown to a massive 13 Gb in size through an imbalance between the rates of amplification and elimination of retrotransposons and satellite repeats. Genes and recombination events are evenly dispersed across chromosomes and the gene space is remarkably compact considering the genome size, though with significant copy number variation driven by tandem duplication. Demonstrating practical application of the genome sequence, we develop a targeted genotyping assay and use high-resolution genome-wide association (GWA) analysis to dissect the genetic basis of hilum colour. The resources presented constitute a genomics-based breeding platform for faba bean, enabling breeders and geneticists to accelerate improvement of sustainable protein production across Mediterranean, subtropical, and northern temperate agro-ecological zones.

plant biology↗

bioRxiv2021

Evolutionary priming and transition to the ectomycorrhizal habit in an iconic lineage of mushroom-forming fungi: is preadaptation a requirement?

The ectomycorrhizal symbiosis is an essential guild of many forested ecosystems and has a dynamic evolutionary history across kingdom Fungi, having independently evolved from diverse types of saprotrophic ancestors. In this study, we seek to identify genomic features of the transition to the ectomycorrhizal habit within the Russulaceae, one of the most diverse lineages of ectomycorrhizal fungi. We present comparative analyses of the pangenome and gene repertoires of 21 species across the order Russulales, including a closely related saprotrophic member of Russulaceae. The ectomycorrhizal Russulaceae is inferred to have originated around the Cretaceous-Paleogene extinction event (73.6-60.1 million years ago (MY)). The genomes of the ectomycorrhizal Russulaceae are characterized by a loss of genes for plant cell-wall degrading enzymes (PCWDEs), an expansion of genome size through increased transposable element (TE) content, a reduction in secondary metabolism clusters, and an association of genes coding for certain secreted proteins with TE "nests". The saprotrophic sister group of the ectomycorrhizal Russulaceae, Gloeopeniophorella convolvens, possesses some of these aspects (e.g., loss of some PCWDE and protease orthologs, TE expansion, reduction in secondary metabolism clusters), resulting from an accelerated rate of gene evolution in the shared ancestor of Russulaceae that predates the evolution of the ectomycorrhizal habit. Genomes of Russulaceae possess a high degree of synteny, including a conserved set of terpene secondary metabolite gene clusters. We hypothesize that the evolution of the ectomycorrhizal habit requires premodification of the genome for plant root association followed by an accelerated rate of gene evolution within the secretome for host-defense circumvention and symbiosis establishment.

evolutionary biology↗