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Burstin, J.

Publications and source records attributed to Burstin, J..

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Combining phenomic and genomic selection for pea breeding improvement

Pea (Pisum sativum L.) is a strategic crop in the development of sustainable agriculture. However, the genetic gain remains limited despite advances in breeding. Genomic selection holds promise to accelerate varietal improvement, but its high implementation cost restricts its use in crops. Phenomic selection, based on near-infrared spectroscopy data, is a cost-effective alternative demonstrated in various crops, but not yet undertaken in pea. This study aims to assess the predictive ability of phenomic selection, alone and combined with genomic selection, for yield-related traits in a panel of elite spring pea lines evaluated across twelve environments. Three cross-validation scenarios were implemented to simulate predictions across different years and locations. Our results show that phenomic prediction is as effective as genomic selection at predicting yield, and is more accurate for seed protein content. The integrative model, combining spectral and molecular data, consistently achieved the highest accuracy for most traits, particularly for complex traits such as grain yield and seed protein. In temporal prediction scenarios, the most accurate predictions were obtained using the spectra data from the same year as phenotyping. In spatial prediction scenarios, predictive accuracy varied by site and year, nevertheless, integrative phenomic-genomic models consistently outperformed univariate approaches. These findings confirm the potential of phenomic selection in pea and underscore the added value of combining near-infrared spectroscopy and genotyping data to improve the prediction of complex traits in breeding programs. In the face of increasing environmental variability, the integrative approach offers a valuable tool for accelerating genetic gain. Key messageThe integration of spectral data into prediction models enhances the predictive ability for complex traits in pea.

genetics↗

A new genome assembly of the pea cultivar Cameor provides resources for functional genomics and genetics

Significant improvements in sequencing technologies have allowed the development of more contiguous genome assemblies in many plant species. The pea genome is characterized by its richness in repeated elements and its long and complex centromeres. This makes its assembly challenging. In this paper, we present an improved version of the genome sequence of the French cultivar Cameor. This sequence was obtained by combining Nanopore and PacBio long-read sequencing, Hi-C contact maps and Bionano maps. The assembly of centromeres was refined using a combination of FISH and ultra-long Nanopore read analyses. Overall, Cameor_v2 genome assembly is a highly continuous pea genome assembly with small total gap size and a large contig N50. In this version, the orientation of chromosomes was revised according to internationally accepted karyotype rules. Gene annotation statistics indicated a high completeness of gene sequences, with most gene sequences with 3 and 5 UTR. This genome assembly with its associated data constitute a useful resource for pea genetics, comparative mapping and functional genomics.

genomics↗

Genome-wide association study of frost tolerance in Vicia faba reveals syntenic loci in cool-season legumes and highlights relevant candidate genes

Cool-season grain legumes are mostly grown over spring and summer due to poor frost tolerance. However, fall-sown varieties often provide higher yields, earlier harvests and avoid late-season drought and heat. Understanding the genetic determinism and molecular basis of frost tolerance is therefore crucial for developing high-performing winter varieties. This study aimed to (1) investigate the genetic architecture of frost tolerance in Vicia faba L. using 247 accessions phenotyped under four field environments, and (2) explore the conservation of frost tolerance loci in cool-season legumes using the OrthoLegKB translational research database. A genome-wide association study identified nineteen V. faba genomic regions with a high density of markers significantly associated with frost tolerance, on all chromosomes. Mapping of frost tolerance QTL from V. faba and related species obtained from the literature onto their respective reference genomes and their integration into OrthoLegKB revealed synteny of major QTL across V. faba, Pisum sativum, and/or Medicago truncatula, particularly near clusters of CBF/DREB1 genes. Frost tolerance QTL at the P. sativum Le locus, which controls internode length, were also syntenic with a frost tolerance QTL in V. faba. Synteny between frost tolerance QTL and those controlling phenology and physiology was found at other loci, suggesting pleiotropy. Finally, expression data from P. sativum and C. arietinum accessions grown under low temperature were considered as information source to highlight potential candidate genes underlying the conserved QTL. Overall, these results provide a valuable resource for understanding and improving frost tolerance in V. faba and other cool-season legumes, including orphan crops by knowledge transfer. The use of OrthoLegKB to explore the genetic and molecular determinism of target traits across species is worth generalising.

plant biology↗

afila, the origin and nature of a major innovation in the history of pea breeding

The afila (af) mutation of Pisum sativum L. (pea) is characterised by leaves that are composed of a basal pair of stipules, a petiole and a branched mass of tendrils. These are bipinnate leaves in which the leaflet primordia are replaced by midrib-like, or terminal tendril, primordia. The phenotype was first reported as a spontaneous mutation in 1953, and several reports of spontaneously occurring af mutants and induced mutations have been published since then. Despite its wide-scale introgression to improve standing ability in combine-harvested dry pea crops, the molecular basis of af has remained unknown. Here, we show that the deletion of two tandemly-arrayed Q-type Cys(2)His(2)-zinc finger transcription factors, viz. PsPALM1a and PsPALM1b, is responsible for the af phenotype. Based on molecular evidence for the presence/absence of seven consecutive pea genes, we identified eight haplotypes in the genomic region of chromosome 2 that harbours af. These haplotypes differ in the presence or absence of PsPALM1a-b and close genes and in the size of the deletion. Representative cultivars and spontaneous or induced mutants were assigned to the different haplotypes. The hitherto unrecognised diversity at the af locus reveals highly rich, unexplored, potential for pea improvement and sheds light on the breeding history of pea. This knowledge can also be used to breed innovative cultivars in related crops.

genetics↗

Assembly of the 81.6 Mb centromere of pea chromosome 6 elucidates the structure and evolution of metapolycentric chromosomes

Centromeres in the legume genera Pisum and Lathyrus exhibit unique morphological characteristics, including extended primary constrictions and multiple separate domains of centromeric chromatin. These so-called metapolycentromeres resemble an intermediate form between monocentric and holocentric types, and therefore provide a great opportunity for studying the transitions between different types of centromere organizations. However, because of the exceedingly large and highly repetitive nature of metapolycentromeres, highly contiguous assemblies needed for these studies are lacking. Here, we report on the assembly and analysis of a 177.6 Mb region of pea (Pisum sativum) chromosome 6, including the 81.6 Mb centromere region (CEN6) and adjacent chromosome arms. Genes, DNA methylation profiles, and most of the repeats were uniformly distributed within the centromere, and their densities in CEN6 and chromosome arms were similar. The exception was an accumulation of satellite DNA in CEN6, where it formed multiple arrays up to 2 Mb in length. Centromeric chromatin, characterized by the presence of the CENH3 protein, was predominantly associated with arrays of three different satellite repeats; however, five other satellites present in CEN6 lacked CENH3. The presence of CENH3 chromatin was found to determine the spatial distribution of the respective satellites during the cell cycle. Finally, oligo-FISH painting experiments, performed using probes specifically designed to label the genomic regions corresponding to CEN6 in Pisum, Lathyrus, and Vicia species, revealed that metapolycentromeres evolved via the expansion of centromeric chromatin into neighboring chromosomal regions and the accumulation of novel satellite repeats. However, in some of these species, centromere evolution also involved chromosomal translocations and centromere repositioning. SignificanceDespite their conserved function, plant centromeres exhibit considerable variation in their morphology and sequence composition. For example, centromere activity is restricted to a single region in monocentric chromosomes, but is distributed along the entire chromosome length in holocentric chromosomes. The principles of centromere evolution that led to this variation are largely unknown, partly due to the lack of high-quality centromere assemblies. Here, we present an assembly of the pea metapolycentromere, a unique type of centromere that represents an intermediate stage between monocentric and holocentric organizations. This study not only provides a detailed insight into sequence organization, but also reveals possible mechanisms for the formation of the metapolycentromere through the spread of centromeric chromatin and the accumulation of satellite DNA.

genomics↗

SNP discovery by exome capture and resequencing in a pea genetic resource collection

Background & SummaryIn addition to being the model plant used by Mendel1 to establish genetic laws, pea (Pisum sativum L., 2n=14) is a major pulse crop cultivated in many temperate regions of the world. In order to face new challenges imposed particularly by global climate change and new regulations targeted at reducing chemical inputs, pea breeders have to take advantage of the genetic diversity present in the Pisum genepool to develop improved, resilient varieties. The aim of this study was to assess the genetic diversity of a pea germplasm collection and allow genome-wide association studies using this collection. To be able to perform genome-wide association approaches with high resolution, genotyping with a large set of genetic markers such as Single Nucleotide Polymorphism (SNP) markers well-spread over the genome is required. Rapid advances in second-generation sequencing technologies and the development of bioinformatic tools have revolutionized the access to and the characterization of available genetic diversity. High-density, high-throughput genotyping has been possible for a large number of species, including those with large and complex genomes2 such as pea (2n=14) which genome size is estimated to be 4.45 Gb3. In this study, which is part of the PeaMUST project4, we used a target capture technology based on pea transcriptome sequences to generate exome-enriched genomic libraries that were further subjected to Illumina sequencing in paired-end mode. This methodology was chosen because whole-genome resequencing is relatively expensive for species with large genomes and because capturing genetic variations in repeated non-coding regions is difficult to achieve or to interpret5. Whole-exome sequencing represented an interesting alternative that focused on coding regions only6,7. Mapping the obtained reads on the reference pea genome sequence enabled the discovery of an abundant set of SNPs. The development of this resource is a crucial cornerstone in research and breeding projects towards boosting the improvement of pea production and quality.

genomics↗

Defining the components of the miRNA156-SPL-miR172 aging pathway in pea and their expression relative to changes in leaf morphology

The timing of developmental phase transitions is crucial for plant reproductive success, and two microRNAs (miRNA), miR156 and miR172, are implicated in the control of these changes, together with their respective SQUAMOSA promoter binding-like (SPL) and APETALA2 (AP2)-like targets. While their patterns of regulation have been studied in a growing range of species, to date they have not been examined in pea (Pisum sativum), an important legume crop and model species. We analysed the recently-released pea genome and defined nine miR156, 21 SPL, four miR172, and five AP2-like genes. Phylogenetic analysis of the SPL genes in pea, Medicago and Arabidopsis confirmed the eight previously defined clades, and identified a ninth potentially legume-specific SPL clade in pea and Medicago. Among the PsSPL, 14 contain a miR156 binding site and all five AP2-like transcription factors in pea include a miR172 binding site. Phylogenetic relationships, expression levels and temporal expression changes identified PsSPL2a/3a/3c/6b/9a/9b/13b/21, PsmiR156d/j and PsmiR172a/d as the most likely of these genes to participate in phase change in pea. Comparisons with leaf morphology suggests that vegetative phase change is unlikely to be definitively marked by a change in leaflet number. In addition, the timing of FT gene induction suggests that the shift from the juvenile to the adult vegetative phase may occur within fourteen days in plants grown under inductive conditions, and calls into question the contribution of miR172/AP2 to the floral transition. This work provides the first insight into the nature of vegetative phase change in pea, and an important foundation for future functional studies.

plant biology↗

Development of a sequence-based reference physical map of pea (Pisum sativum L.)

Whole genome profiling (WGP) is a sequence-based physical mapping technology and uses sequence tags generated by next generation sequencing for construction of bacterial artificial chromosome (BAC) contigs of complex genomes. The physical map provides a framework for assembly of genome sequence and information for localization of genes that are difficult to find through positional cloning. To address the challenges of accurate assembly of the pea genome (~4.2 GB of which approximately 85% is repetitive sequences), we have adopted the WGP technology for assembly of a pea BAC library. Multi-dimensional pooling of 295,680 BAC clones and sequencing the ends of restriction fragments of pooled DNA generated 1,814 million high quality reads, of which 825 million were deconvolutable to 1.11 million unique WGP sequence tags. These WGP tags were used to assemble 220,013 BACs into contigs. Assembly of the BAC clones using the modified Fingerprinted Contigs (FPC) program has resulted in 13,040 contigs, consisting of 213,719 BACs, and 6,294 singleton BACs. The average contig size is 0.33 Mbp and the N50 contig size is 0.62 Mbp. WGPTM technology has proved to provide a robust physical map of the pea genome, which would have been difficult to assemble using traditional restriction digestion based methods. This sequence-based physical map will be useful to assemble the genome sequence of pea. Additionally, the 1.1 million WGP tags will support efficient assignment of sequence scaffolds to the BAC clones, and thus an efficient sequencing of BAC pools with targeted genome regions of interest.

genomics↗