Biology subjects

Marcon, C.

Publications and source records attributed to Marcon, C..

7 recordsLinked to original sources

bioRxiv2026

Specification of embryonic shoot stem cells via a small RNA-driven morphogenic circuit

The specification of embryonic stem cells capable of self-renewing and differentiation into virtually any cell type, is one of the most consequential events in the development of a multicellular organism. Yet the mechanisms establishing embryonic stem cell fate remain poorly understood, particularly in monocotyledonous cereals. Using the classic mutant leafbladeless1-raggedseedling1, we show that the small RNA tasiARF acts as a primary epidermis-derived morphogenic signal that organizes shoot stem cell specification in the maize embryo. tasiARF restricts expression of the AUXIN RESPONSE FACTOR 3 (ARF3) transcription factor, which modulates cell wall mechanics and guides the differential localization of PIN-FORMED (PIN) auxin efflux carriers, establishing a localized auxin minimum permissive for stem cell fate. Interestingly, loss of this auxin minimum and the associated shoot stem cell defects in tasiARF-deficient embryos are buffered by natural variation at a quantitative trait locus (QTL) controlling expression of MICROTUBULE-ASSOCIATED PROTEIN 65-3 (MAP65-3), a critical factor determining cell division orientation, which reshapes auxin dynamics and restores stem cell specification, and is itself under tasiARF-ARF3 control. Thus, embryonic shoot stem cell specification in maize is governed by an intricate morphogenic circuit that couples small RNA-mediated positional information to a self-stabilizing network interdependently linking cell wall mechanics, auxin signaling, and cell division patterning. This mechanistic framework reveals the redeployment of an ancient small RNA pathway as a lineage-specific innovation to establish a conserved, stem cell-permissive low auxin environment within the divergent embryonic architecture of monocotyledonous cereals. More broadly, it identifies molecular entry points for the engineering of embryogenic competence and regeneration capacity for the improvement of cereal crops.

plant biology↗

bioRxiv2025

Pathogenic fungus exploits the lateral root regulators to induce pluripotency in maize shoots

Biotrophic plant pathogens secrete effector molecules to redirect and exploit endogenous signaling and developmental pathways in their favor. The biotrophic fungus Ustilago maydis causes galls on all aerial parts of maize. However, identification and characterization of the responsible gall-inducing effectors and corresponding plant signaling pathway(s) are largely elusive. Here we reveal molecular components acting downstream of a group of plant TOPLESS (TPL)- corepressor interacting fungal effectors that are directly involved in gall formation. We classify these effectors into two classes based on distinct phenotypic responses when individually expressed in planta. While class I responses are characterized by leaf chlorosis, transgenic plants expressing class II TPL-interacting protein (Tip) effectors show a derepression of the AtARF7/AtARF19 branch of auxin signaling, resulting in pluripotent calli formation without the external addition of phytohormones. Subsequent comparative transcriptomics in maize also demonstrates a highly significant overlap of genes up-regulated during U. maydis-triggered leaf gall formation and during the developmental initiation of lateral root formation. This suggests that U. maydis can hijack the lateral root initiation pathway to induce galls in maize shoots. We demonstrate that underlying this is the transcriptional upregulation of downstream LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors. Maize mutants in two LBD genes (ra2, rtcs) led to significantly reduced gall formation following U. maydis infection on homozygous mutants. This study reveals a set of dominantly acting cell proliferation-inducing fungal effectors and provides novel insight into plant developmental pathways that can be hijacked by biotrophic pathogens to induce gall formation.

plant biology↗

bioRxiv2024

Embracing native diversity to enhance maximum quantum efficiency of photosystem II in maize (Zea mays L.)

Sustainability of maize cultivation would benefit tremendously from early sowing but is hampered by low temperatures during early development in temperate climate. We show that allelic variation of subunit M of NADH-dehydrogenase-like (NDH) complex (ndhm1), discovered in a European maize landrace affects several quantitative traits relevant during early development in cold climates through NDH-mediated cyclic electron transport (CET) around photosystem I, a process crucial for photosynthesis. Starting from a genome-wide association study (GWAS) for maximum potential quantum yield of photosystem II in dark-adapted leaves (Fv/Fm) we capitalized on large phenotypic effects of a hAT transposon insertion in ndhm1 on quantitative traits early plant height (EPH), Fv/Fm, chlorophyll content and cold tolerance caused by reduced protein levels of NDHM and associated NDH components. Analysis of the native allelic series of ndhm1 revealed a rare allele of ndhm1 which is associated with small albeit significant effects on maximum potential quantum yield of photosystem II in dark- and light adapted leaves (Fv/Fm, {Phi}PSII) and early plant height compared to common alleles. Our work showcases the extraction of novel, favorable alleles from locally adapted landraces, offering an efficient strategy for broadening the genetic variation of elite germplasm by breeding or genome editing.

plant biology↗

bioRxiv2024

Catechol acetylglucose: A newly identified benzoxazinoid-regulated defensive metabolite in maize

An enormous diversity of specialized metabolites is produced in the plant kingdom, with each individual plant synthesizing thousands of these compounds. Previous research showed that benzoxazinoids, the most abundant class of specialized metabolites in maize, also function as signaling molecules by regulating the production callose as a defense response. In this study, we identified catechol acetylglucose (CAG) as a benzoxazinoid-regulated metabolite that is produced from salicylic acid via catechol and catechol-glucoside. Genome wide association studies of CAG abundance identified a gene encoding a predicted acetyltransferase. Knockout of this gene resulted in maize plants that lack CAG and over-accumulate catechol glucoside. Upon tissue disruption, maize plants accumulate catechol, which inhibits Spodoptera frugiperda (fall armyworm) growth. Analysis of caterpillar frass showed that S. frugiperda detoxifies catechol by glycosylation, and the efficiency of catechol glycosylation was correlated with S. frugiperda growth on a catechol-containing diet. Thus, the success of S. frugiperda as an agricultural pest may depend partly on its ability to detoxify catechol, which is produced as a defensive metabolite by maize plants.

plant biology↗

bioRxiv2024

Expanding the BonnMu sequence-indexed repository of transposon induced maize (Zea mays L.) mutations in dent and flint germplasm

The BonnMu resource is a transposon-tagged mutant collection designed for functional genomics studies in maize. To expand this resource, we crossed an active Mutator (Mu) line with dent (B73, Co125) and flint (DK105, EP1 and F7) germplasm, resulting in the generation of 8,064 mutagenized BonnMu F2-families. Sequencing of these Mu-tagged families revealed 425,924 heritable Mu insertions affecting 36,612 (83%) of the 44,303 high-confidence gene models of maize (B73v5). On average, we observed 12 Mu insertions per gene (425,924 total insertions/ 36,612 affected genes) and 53 insertions per BonnMu F2-family (425,924 total insertions/ 8,064 families). Mu insertions and photos of seedling phenotypes from segregating BonnMu F2-families can be accessed through the Maize Genetics and Genomics Database (MaizeGDB). Downstream examination via the automated Mutant-seq Workflow Utility (MuWU) identified 94% of the germinal insertion sites in genic regions and only a small fraction of 6% inserting in non-coding intergenic sequences of the genome. Consistently, Mu insertions aligned with gene-dense chromosomal arms. In total, 42% of all BonnMu insertions were located in the 5 untranslated region (UTR) of genes, corresponding to accessible chromatin. Furthermore, for 38% of the insertions (163,843 of 425,924 total insertions) Mu1, Mu8 and MuDR were confirmed to be the causal Mu elements. Our publicly accessible European BonnMu resource has archived insertions covering two major germplasm groups, thus facilitating both forward and reverse genetics studies.

genomics↗

bioRxiv2023

Heritable maize microbiomes contribute to local adaptation and host stress resilience

Beneficial interactions with microorganisms are pivotal for crop performance and resilience. However, it remains unclear how heritable the microbiome is with respect to the host plant genotype and to what extent host genetic mechanisms can modulate plant-microbe interactions in the face of environmental stress. Here, we surveyed the root and rhizosphere microbiome of 129 accessions of locally adapted Zea mays, sourced from diverse habitats and grown under control and different stress conditions. We quantified treatment and host genotype effects on the microbiome. Plant genotype and source environment were predictive of microbiome composition. Genome wide association analysis identified host genetic variants linked to both rhizosphere microbiome composition and source environment. We identified transposon insertions in a candidate gene linked to both the abundance of a keystone microbe Massilia and source total soil nitrogen, finding mutant plants to show a reduction in lateral root density. We conclude that locally adapted maize varieties exert patterns of genetic control on their root and rhizosphere microbiomes that follow variation in their home environments, consistent with a role in tolerance to prevailing stress.

genetics↗

bioRxiv2017

European Flint reference sequences complement the maize pan-genome

The genomic diversity of maize is reflected by a large number of SNPs and substantial structural variation. Here, we report the de novo assembly of two European Flint maize lines to remedy the scarcity of sequence resources for the Flint pool. EP1 and F7 are important founder lines of European hybrid breeding programs. The lines were sequenced on an Illumina platform at 320X and 225X coverage. Using NRGene{acute}s DeNovoMAGIC 2.0 technology, pseudochromosomes were assembled encompassing a total of 2,463 Mb for EP1 and 2,405 Mb for F7. Structural and functional annotation of the two genomes is currently in progress. The two high-quality de novo assemblies complement the existing maize pan-genome and will pave the way for future functional and comparative studies.

genomics↗