Jeong-Hwan Mun | Myongji University (original) (raw)

Papers by Jeong-Hwan Mun

Research paper thumbnail of Additional file 5: of Draft genome sequence of wild Prunus yedoensis reveals massive inter-specific hybridization between sympatric flowering cherries

Table S4. Summary of repetitive sequences identified in the draft genome of wild P. yedoensis. (X... more Table S4. Summary of repetitive sequences identified in the draft genome of wild P. yedoensis. (XLSX 12 kb)

Research paper thumbnail of Phenotypic Analysis Between Parents and Their Reciprocal F1 Hybrids in Phalaenopsis

Korean Society For Horticultural Science, Oct 1, 2015

Research paper thumbnail of Additional file 6: of Draft genome sequence of wild Prunus yedoensis reveals massive inter-specific hybridization between sympatric flowering cherries

Table S5. Statistics of gene models predicted from the draft genome of wild P. yedoensis. (XLSX 1... more Table S5. Statistics of gene models predicted from the draft genome of wild P. yedoensis. (XLSX 10 kb)

Research paper thumbnail of P3) A Pipeline for high throughput SNP and InDel discovery from intron of Brassica rapa

Research paper thumbnail of Marker integration and development of Fluidigm/KASP assays for high-throughput genotyping of radish

Horticulture, Environment, and Biotechnology, 2020

Radish (Raphanus sativus L.) is a representative root crop of the Brassicaceae family and is impo... more Radish (Raphanus sativus L.) is a representative root crop of the Brassicaceae family and is important to the vegetable seed industry in East Asia. Due to its agronomic importance, various molecular markers, genetic maps, genomic resources, and genome assemblies of radish have been developed during the past decade. Marker integration and comparative mapping using these resources will accelerate genetic improvements in radish cultivars. With the goal of establishing a marker-based high-throughput genetic analysis tool, we integrated 3765 nonredundant genetic markers into the Rs1.0 reference genome and converted them into 1182 single nucleotide polymorphism (SNP) markers via whole-genome resequencing data of the mapping parents 'WK10039' and 'WK10024'. A genetic map covering 721.3 cM with 768 framework loci was constructed by analyzing these SNP conversion markers in the F 2 mapping population, which was composed of 93 individuals. Comparison of this map with the Rs1.0 reference genome and other linkage maps showed the physical and genetic correlations of the markers. To develop a high-throughput genotyping system for large accessions or populations with smaller numbers of SNPs, 674 Fluidigm and 68 kompetitive allele-specific PCR (KASP) markers were validated. Application of the 68 KASP assays to 127 commercial cultivars enabled successful identification and classification of genotypes; 11 KASP markers constituted the minimum marker set. The SNP markers used to construct the genetic maps will be a useful resource in research on radish and should lead to low-cost, accurate, and high-throughput genotyping platforms.

Research paper thumbnail of Legume Comparative Genomics using Cross-species Gene-specific Markers

Research paper thumbnail of Association Mapping Reveals the Role for Candidate Genes on A09 in the Regulation of Glucosinolate Levels in Brassica rapa

Research paper thumbnail of An improved Raphanus sativus cv. WK10039 genome localizes centromeres, uncovers variation of DNA methylation and resolves arrangement of the ancestral Brassica genome blocks in radish chromosomes

Theoretical and Applied Genetics, 2022

KEY MESSAGE This study presents an improved genome of Raphanus sativus cv. WK10039 uncovering cen... more KEY MESSAGE This study presents an improved genome of Raphanus sativus cv. WK10039 uncovering centromeres and differentially methylated regions of radish chromosomes. Comprehensive genome comparison of radish and diploid Brassica species of U's triangle reveals that R. sativus arose from the Brassica B genome lineage and is a sibling species of B. nigra. Radish (Raphanus sativus L.) is a key root vegetable crop closely related to the Brassica crop species of the family Brassicaceae. We reported a draft genome of R. sativus cv. WK10039 (Rs1.0), which had 54.6 Mb gaps. To study the radish genome and explore previously unknown regions, we generated an improved genome assembly (Rs2.0) by long-read sequencing and high-resolution genome-wide mapping of chromatin interactions. Rs2.0 was 434.9 Mb in size with 0.27 Mb gaps, and the N50 scaffold length was 37.3 Mb (40-fold larger assembly compared to Rs1.0). Approximately 38% of Rs2.0 was comprised of repetitive sequences, and 52,768 protein-coding genes and 4845 non-protein-coding genes were predicted and annotated. The improved contiguity and coverage of Rs2.0, along with the detection of highly methylated regions, enabled localization of centromeres where R. sativus-specific centromere-associated repeats, full-length OTA and CRM LTR-Gypsy retrotransposons, hAT-Ac, CMC-EnSpm and Helitron DNA transposons, and sequences highly homologous to B. nigra centromere-specific CENH3-associated CL sequences were enriched. Whole-genome bisulfite sequencing combined with mRNA sequencing identified differential epigenetic marks in the radish genome related to tissue development. Synteny comparison and genomic distance analysis of radish and three diploid Brassica species of U's triangle suggested that the radish genome arose from the Brassica B genome lineage through unique rearrangement of the triplicated ancestral Brassica genome after splitting of the Brassica A/C and B genomes.

Research paper thumbnail of Epitypification of Prunus × nudiflora (Rosaceae), a natural hybrid species in Jeju Island, Korea

Journal of Asia-Pacific Biodiversity, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Additional file 3: of Draft genome sequence of wild Prunus yedoensis reveals massive inter-specific hybridization between sympatric flowering cherries

Table S2. Statistics of transcriptome sequence data of wild P. yedoensis (Pyn-Jeju2) used in this... more Table S2. Statistics of transcriptome sequence data of wild P. yedoensis (Pyn-Jeju2) used in this study. (XLSX 11 kb)

Research paper thumbnail of A physical map of Brassica oleracea shows complexity of chromosomal changes following recursive paleopolyploidizations

BMC Genomics, 2011

Background: Evolution of the Brassica species has been recursively affected by polyploidy events,... more Background: Evolution of the Brassica species has been recursively affected by polyploidy events, and comparison to their relative, Arabidopsis thaliana, provides means to explore their genomic complexity. Results: A genome-wide physical map of a rapid-cycling strain of B. oleracea was constructed by integrating highinformation-content fingerprinting (HICF) of Bacterial Artificial Chromosome (BAC) clones with hybridization to sequence-tagged probes. Using 2907 contigs of two or more BACs, we performed several lines of comparative genomic analysis. Interspecific DNA synteny is much better preserved in euchromatin than heterochromatin, showing the qualitative difference in evolution of these respective genomic domains. About 67% of contigs can be aligned to the Arabidopsis genome, with 96.5% corresponding to euchromatic regions, and 3.5% (shown to contain repetitive sequences) to pericentromeric regions. Overgo probe hybridization data showed that contigs aligned to Arabidopsis euchromatin contain~80% of low-copy-number genes, while genes with high copy number are much more frequently associated with pericentromeric regions. We identified 39 interchromosomal breakpoints during the diversification of B. oleracea and Arabidopsis thaliana, a relatively high level of genomic change since their divergence. Comparison of the B. oleracea physical map with Arabidopsis and other available eudicot genomes showed appreciable 'shadowing' produced by more ancient polyploidies, resulting in a web of relatedness among contigs which increased genomic complexity. Conclusions: A high-resolution genetically-anchored physical map sheds light on Brassica genome organization and advances positional cloning of specific genes, and may help to validate genome sequence assembly and alignment to chromosomes. All the physical mapping data is freely shared at a WebFPC site (http://lulu.pgml.uga.edu/fpc/WebAGCoL/brassica/ WebFPC/; Temporarily password-protected: account: pgml; password: 123qwe123.

Research paper thumbnail of A Reference Genetic Map of Korean Radish Constructed by Genotyping by Sequencing

Research paper thumbnail of Development Gene-based Markers for Breeding of Seedless Grape

Research paper thumbnail of Sequencing of the Radish Genome

Research paper thumbnail of Development of Resistance Gene-based Molecular Markers through High-throughput Genotyping from Brassica rapa

Research paper thumbnail of Identification of candidate domestication regions in the radish genome based on high-depth resequencing analysis of 17 genotypes

TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, Jan 4, 2016

This study provides high-quality variation data of diverse radish genotypes. Genome-wide SNP comp... more This study provides high-quality variation data of diverse radish genotypes. Genome-wide SNP comparison along with RNA-seq analysis identified candidate genes related to domestication that have potential as trait-related markers for genetics and breeding of radish. Radish (Raphanus sativus L.) is an annual root vegetable crop that also encompasses diverse wild species. Radish has a long history of domestication, but the origins and selective sweep of cultivated radishes remain controversial. Here, we present comprehensive whole-genome resequencing analysis of radish to explore genomic variation between the radish genotypes and to identify genetic bottlenecks due to domestication in Asian cultivars. High-depth resequencing and multi-sample genotyping analysis of ten cultivated and seven wild accessions obtained 4.0 million high-quality homozygous single-nucleotide polymorphisms (SNPs)/insertions or deletions. Variation analysis revealed that Asian cultivated radish types are closely ...

Research paper thumbnail of BraMRs: A Novel Brassica rapa miRNA Database Based on Small RNA Deep-Sequencing

MicroRNAs (miRNAs) are one of evolutionary conserved functional non-coding small RNAs with approx... more MicroRNAs (miRNAs) are one of evolutionary conserved functional non-coding small RNAs with approximately ~24 nucleotides. Because the first draft genome sequence and its annotation for Brassica rapa which is one of the two ancestral species of oilseed rape is currently available, identification of miRNAs and their target prediction in the genome can be explored by comparison with miRNA families in A. thaliana. However computational methods often provide unreliable candidate miRNAs due to lack of gene structure information and genome wide experimental data. For this reason we intend to provide more reliable prediction of B. rapa miRNAs on the genome based on high throughput Illumina small RNA deep-sequencing data. We developed a novel miRNA database of B. rapa, BraMRs, that integrated B. rapa miRNA identification, target prediction, and functional annotation for targets. BraMRs identifies putative miRNAs based on combination of similarity search and Illumina small RNA sequencing data...

Research paper thumbnail of Identification and characterization of the phytocystatin family from Brassica rapa

Research paper thumbnail of ORIGINAL PAPER Auxin response factor gene family in Brassica rapa: genomic organization, divergence, expression, and evolution

rapa genome enabled us to undertake a genome-wide identification and functional study of the gene... more rapa genome enabled us to undertake a genome-wide identification and functional study of the gene families related to the morphological diversity and agronomic traits of Brassica crops. In this study, we identified the auxin response factor (ARF) gene family, which is one of the key regulators of auxin-mediated plant growth and develop-ment in the B. rapa genome. A total of 31 ARF genes were identified in the genome. Phylogenetic and evolutionary analyses suggest that ARF genes fell into four major classes and were amplified in the B. rapa genome as a result of a recent whole genome triplication after speciation from Arabidopsis thaliana. Despite its recent hexaploid ancestry, B. rapa includes a relatively small number of ARF genes compared with the 23 members in A. thaliana, presumably due to a paralog reduction related to repetitive sequence insertion into promoter and non-coding transcribed region of the genes. Comparative genomic and mRNA sequencing analyses demonstrated that 27...

Research paper thumbnail of The CCAAT box-binding transcription factor NF-YA1 controls rhizobial infection

Journal of Experimental Botany, 2014

Symbiosis between legume plants and soil rhizobia culminates in the formation of a novel root org... more Symbiosis between legume plants and soil rhizobia culminates in the formation of a novel root organ, the 'nodule', containing bacteria differentiated as facultative nitrogen-fixing organelles. MtNF-YA1 is a Medicago truncatula CCAAT box-binding transcription factor (TF), formerly called HAP2-1, highly expressed in mature nodules and required for nodule meristem function and persistence. Here a role for MtNF-YA1 during early nodule development is demonstrated. Detailed expression analysis based on RNA sequencing, quantitiative real-time PCR (qRT-PCR), as well as promoter-β-glucuronidase (GUS) fusions reveal that MtNF-YA1 is first induced at the onset of symbiotic development during preparation for, and initiation and progression of, symbiotic infection. Moreover, using a new knockout mutant, Mtnf-ya1-1, it is shown that MtNF-YA1 controls infection thread (IT) progression from initial root infection through colonization of nodule tissues. Extensive confocal and electronic microscopic observations suggest that the bulbous and erratic IT growth phenotypes observed in Mtnf-ya1-1 could be a consequence of the fact that walls of ITs in this mutant are thinner and less coherent than in the wild type. It is proposed that MtNF-YA1 controls rhizobial infection progression by regulating the formation and the wall of ITs.

Research paper thumbnail of Additional file 5: of Draft genome sequence of wild Prunus yedoensis reveals massive inter-specific hybridization between sympatric flowering cherries

Table S4. Summary of repetitive sequences identified in the draft genome of wild P. yedoensis. (X... more Table S4. Summary of repetitive sequences identified in the draft genome of wild P. yedoensis. (XLSX 12 kb)

Research paper thumbnail of Phenotypic Analysis Between Parents and Their Reciprocal F1 Hybrids in Phalaenopsis

Korean Society For Horticultural Science, Oct 1, 2015

Research paper thumbnail of Additional file 6: of Draft genome sequence of wild Prunus yedoensis reveals massive inter-specific hybridization between sympatric flowering cherries

Table S5. Statistics of gene models predicted from the draft genome of wild P. yedoensis. (XLSX 1... more Table S5. Statistics of gene models predicted from the draft genome of wild P. yedoensis. (XLSX 10 kb)

Research paper thumbnail of P3) A Pipeline for high throughput SNP and InDel discovery from intron of Brassica rapa

Research paper thumbnail of Marker integration and development of Fluidigm/KASP assays for high-throughput genotyping of radish

Horticulture, Environment, and Biotechnology, 2020

Radish (Raphanus sativus L.) is a representative root crop of the Brassicaceae family and is impo... more Radish (Raphanus sativus L.) is a representative root crop of the Brassicaceae family and is important to the vegetable seed industry in East Asia. Due to its agronomic importance, various molecular markers, genetic maps, genomic resources, and genome assemblies of radish have been developed during the past decade. Marker integration and comparative mapping using these resources will accelerate genetic improvements in radish cultivars. With the goal of establishing a marker-based high-throughput genetic analysis tool, we integrated 3765 nonredundant genetic markers into the Rs1.0 reference genome and converted them into 1182 single nucleotide polymorphism (SNP) markers via whole-genome resequencing data of the mapping parents 'WK10039' and 'WK10024'. A genetic map covering 721.3 cM with 768 framework loci was constructed by analyzing these SNP conversion markers in the F 2 mapping population, which was composed of 93 individuals. Comparison of this map with the Rs1.0 reference genome and other linkage maps showed the physical and genetic correlations of the markers. To develop a high-throughput genotyping system for large accessions or populations with smaller numbers of SNPs, 674 Fluidigm and 68 kompetitive allele-specific PCR (KASP) markers were validated. Application of the 68 KASP assays to 127 commercial cultivars enabled successful identification and classification of genotypes; 11 KASP markers constituted the minimum marker set. The SNP markers used to construct the genetic maps will be a useful resource in research on radish and should lead to low-cost, accurate, and high-throughput genotyping platforms.

Research paper thumbnail of Legume Comparative Genomics using Cross-species Gene-specific Markers

Research paper thumbnail of Association Mapping Reveals the Role for Candidate Genes on A09 in the Regulation of Glucosinolate Levels in Brassica rapa

Research paper thumbnail of An improved Raphanus sativus cv. WK10039 genome localizes centromeres, uncovers variation of DNA methylation and resolves arrangement of the ancestral Brassica genome blocks in radish chromosomes

Theoretical and Applied Genetics, 2022

KEY MESSAGE This study presents an improved genome of Raphanus sativus cv. WK10039 uncovering cen... more KEY MESSAGE This study presents an improved genome of Raphanus sativus cv. WK10039 uncovering centromeres and differentially methylated regions of radish chromosomes. Comprehensive genome comparison of radish and diploid Brassica species of U's triangle reveals that R. sativus arose from the Brassica B genome lineage and is a sibling species of B. nigra. Radish (Raphanus sativus L.) is a key root vegetable crop closely related to the Brassica crop species of the family Brassicaceae. We reported a draft genome of R. sativus cv. WK10039 (Rs1.0), which had 54.6 Mb gaps. To study the radish genome and explore previously unknown regions, we generated an improved genome assembly (Rs2.0) by long-read sequencing and high-resolution genome-wide mapping of chromatin interactions. Rs2.0 was 434.9 Mb in size with 0.27 Mb gaps, and the N50 scaffold length was 37.3 Mb (40-fold larger assembly compared to Rs1.0). Approximately 38% of Rs2.0 was comprised of repetitive sequences, and 52,768 protein-coding genes and 4845 non-protein-coding genes were predicted and annotated. The improved contiguity and coverage of Rs2.0, along with the detection of highly methylated regions, enabled localization of centromeres where R. sativus-specific centromere-associated repeats, full-length OTA and CRM LTR-Gypsy retrotransposons, hAT-Ac, CMC-EnSpm and Helitron DNA transposons, and sequences highly homologous to B. nigra centromere-specific CENH3-associated CL sequences were enriched. Whole-genome bisulfite sequencing combined with mRNA sequencing identified differential epigenetic marks in the radish genome related to tissue development. Synteny comparison and genomic distance analysis of radish and three diploid Brassica species of U's triangle suggested that the radish genome arose from the Brassica B genome lineage through unique rearrangement of the triplicated ancestral Brassica genome after splitting of the Brassica A/C and B genomes.

Research paper thumbnail of Epitypification of Prunus × nudiflora (Rosaceae), a natural hybrid species in Jeju Island, Korea

Journal of Asia-Pacific Biodiversity, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Additional file 3: of Draft genome sequence of wild Prunus yedoensis reveals massive inter-specific hybridization between sympatric flowering cherries

Table S2. Statistics of transcriptome sequence data of wild P. yedoensis (Pyn-Jeju2) used in this... more Table S2. Statistics of transcriptome sequence data of wild P. yedoensis (Pyn-Jeju2) used in this study. (XLSX 11 kb)

Research paper thumbnail of A physical map of Brassica oleracea shows complexity of chromosomal changes following recursive paleopolyploidizations

BMC Genomics, 2011

Background: Evolution of the Brassica species has been recursively affected by polyploidy events,... more Background: Evolution of the Brassica species has been recursively affected by polyploidy events, and comparison to their relative, Arabidopsis thaliana, provides means to explore their genomic complexity. Results: A genome-wide physical map of a rapid-cycling strain of B. oleracea was constructed by integrating highinformation-content fingerprinting (HICF) of Bacterial Artificial Chromosome (BAC) clones with hybridization to sequence-tagged probes. Using 2907 contigs of two or more BACs, we performed several lines of comparative genomic analysis. Interspecific DNA synteny is much better preserved in euchromatin than heterochromatin, showing the qualitative difference in evolution of these respective genomic domains. About 67% of contigs can be aligned to the Arabidopsis genome, with 96.5% corresponding to euchromatic regions, and 3.5% (shown to contain repetitive sequences) to pericentromeric regions. Overgo probe hybridization data showed that contigs aligned to Arabidopsis euchromatin contain~80% of low-copy-number genes, while genes with high copy number are much more frequently associated with pericentromeric regions. We identified 39 interchromosomal breakpoints during the diversification of B. oleracea and Arabidopsis thaliana, a relatively high level of genomic change since their divergence. Comparison of the B. oleracea physical map with Arabidopsis and other available eudicot genomes showed appreciable 'shadowing' produced by more ancient polyploidies, resulting in a web of relatedness among contigs which increased genomic complexity. Conclusions: A high-resolution genetically-anchored physical map sheds light on Brassica genome organization and advances positional cloning of specific genes, and may help to validate genome sequence assembly and alignment to chromosomes. All the physical mapping data is freely shared at a WebFPC site (http://lulu.pgml.uga.edu/fpc/WebAGCoL/brassica/ WebFPC/; Temporarily password-protected: account: pgml; password: 123qwe123.

Research paper thumbnail of A Reference Genetic Map of Korean Radish Constructed by Genotyping by Sequencing

Research paper thumbnail of Development Gene-based Markers for Breeding of Seedless Grape

Research paper thumbnail of Sequencing of the Radish Genome

Research paper thumbnail of Development of Resistance Gene-based Molecular Markers through High-throughput Genotyping from Brassica rapa

Research paper thumbnail of Identification of candidate domestication regions in the radish genome based on high-depth resequencing analysis of 17 genotypes

TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, Jan 4, 2016

This study provides high-quality variation data of diverse radish genotypes. Genome-wide SNP comp... more This study provides high-quality variation data of diverse radish genotypes. Genome-wide SNP comparison along with RNA-seq analysis identified candidate genes related to domestication that have potential as trait-related markers for genetics and breeding of radish. Radish (Raphanus sativus L.) is an annual root vegetable crop that also encompasses diverse wild species. Radish has a long history of domestication, but the origins and selective sweep of cultivated radishes remain controversial. Here, we present comprehensive whole-genome resequencing analysis of radish to explore genomic variation between the radish genotypes and to identify genetic bottlenecks due to domestication in Asian cultivars. High-depth resequencing and multi-sample genotyping analysis of ten cultivated and seven wild accessions obtained 4.0 million high-quality homozygous single-nucleotide polymorphisms (SNPs)/insertions or deletions. Variation analysis revealed that Asian cultivated radish types are closely ...

Research paper thumbnail of BraMRs: A Novel Brassica rapa miRNA Database Based on Small RNA Deep-Sequencing

MicroRNAs (miRNAs) are one of evolutionary conserved functional non-coding small RNAs with approx... more MicroRNAs (miRNAs) are one of evolutionary conserved functional non-coding small RNAs with approximately ~24 nucleotides. Because the first draft genome sequence and its annotation for Brassica rapa which is one of the two ancestral species of oilseed rape is currently available, identification of miRNAs and their target prediction in the genome can be explored by comparison with miRNA families in A. thaliana. However computational methods often provide unreliable candidate miRNAs due to lack of gene structure information and genome wide experimental data. For this reason we intend to provide more reliable prediction of B. rapa miRNAs on the genome based on high throughput Illumina small RNA deep-sequencing data. We developed a novel miRNA database of B. rapa, BraMRs, that integrated B. rapa miRNA identification, target prediction, and functional annotation for targets. BraMRs identifies putative miRNAs based on combination of similarity search and Illumina small RNA sequencing data...

Research paper thumbnail of Identification and characterization of the phytocystatin family from Brassica rapa

Research paper thumbnail of ORIGINAL PAPER Auxin response factor gene family in Brassica rapa: genomic organization, divergence, expression, and evolution

rapa genome enabled us to undertake a genome-wide identification and functional study of the gene... more rapa genome enabled us to undertake a genome-wide identification and functional study of the gene families related to the morphological diversity and agronomic traits of Brassica crops. In this study, we identified the auxin response factor (ARF) gene family, which is one of the key regulators of auxin-mediated plant growth and develop-ment in the B. rapa genome. A total of 31 ARF genes were identified in the genome. Phylogenetic and evolutionary analyses suggest that ARF genes fell into four major classes and were amplified in the B. rapa genome as a result of a recent whole genome triplication after speciation from Arabidopsis thaliana. Despite its recent hexaploid ancestry, B. rapa includes a relatively small number of ARF genes compared with the 23 members in A. thaliana, presumably due to a paralog reduction related to repetitive sequence insertion into promoter and non-coding transcribed region of the genes. Comparative genomic and mRNA sequencing analyses demonstrated that 27...

Research paper thumbnail of The CCAAT box-binding transcription factor NF-YA1 controls rhizobial infection

Journal of Experimental Botany, 2014

Symbiosis between legume plants and soil rhizobia culminates in the formation of a novel root org... more Symbiosis between legume plants and soil rhizobia culminates in the formation of a novel root organ, the 'nodule', containing bacteria differentiated as facultative nitrogen-fixing organelles. MtNF-YA1 is a Medicago truncatula CCAAT box-binding transcription factor (TF), formerly called HAP2-1, highly expressed in mature nodules and required for nodule meristem function and persistence. Here a role for MtNF-YA1 during early nodule development is demonstrated. Detailed expression analysis based on RNA sequencing, quantitiative real-time PCR (qRT-PCR), as well as promoter-β-glucuronidase (GUS) fusions reveal that MtNF-YA1 is first induced at the onset of symbiotic development during preparation for, and initiation and progression of, symbiotic infection. Moreover, using a new knockout mutant, Mtnf-ya1-1, it is shown that MtNF-YA1 controls infection thread (IT) progression from initial root infection through colonization of nodule tissues. Extensive confocal and electronic microscopic observations suggest that the bulbous and erratic IT growth phenotypes observed in Mtnf-ya1-1 could be a consequence of the fact that walls of ITs in this mutant are thinner and less coherent than in the wild type. It is proposed that MtNF-YA1 controls rhizobial infection progression by regulating the formation and the wall of ITs.