The wild progenitor of common-bean has an exceptionally large distribution from northern Mexico to northwestern Argentina, unusual among crop wild progenitors. This research sought to document major events of range expansion that led to this distribution and associated environmental changes. Through the use of genotyping-by-sequencing (∼20,000 SNPs) and geographic information systems applied to a sample of 246 accessions of wild Phaseolus vulgaris, including 157 genotypes of the Mesoamerican, 77 of the southern Andean, and 12 of the Northern Peru–Ecuador gene pools, we identified five geographically distinct subpopulations. Three of these subpopulations belong to the Mesoamerican gene pool (Northern and Central Mexico, Oaxaca, and Southern Mexico, Central America and northern South America) and one each to the Northern Peru–Ecuador (PhI) and the southern Andean gene pools. The five subpopulations were distributed in different floristic provinces of the Neotropical seasonally dry forest and showed distinct distributions for temperature and rainfall resulting in decreased local potential evapotranspiration (PhI and southern Andes groups) compared with the two Mexican groups. Three of these subpopulations represent long-distance dispersal events from Mesoamerica into Northern Peru–Ecuador, southern Andes, and Central America and Colombia, in chronological order. Of particular note is that the dispersal to Northern Peru–Ecuador markedly predates the dispersal to the southern Andes (∼400 vs. ∼100 ky), consistent with the ancestral nature of the phaseolin seed protein and chloroplast sequences observed in the PhI group. Seed dispersal in common bean can be, therefore, described at different spatial and temporal scales, from localized, annual seed shattering to long‐distance, evolutionarily rare migration.

TitleGenome-wide identification of SNPs and copy number variation in common bean (Phaseolus vulgaris L.) using genotyping-by-sequencing (GBS) Next Generation Sequencing (NGS) technologies have increased markedly the throughput of genetic studies, allowing the identification of several thousands of SNPs within a single experiment. Even though sequencing cost is rapidly decreasing, the price for whole genome re-sequencing of a large number of individuals is still costly, especially in plants with a large and highly redundant genome. In recent years, several reduced representation library (RRL) approaches has been developed for reducing the sequencing cost per individual. Among them, Genotyping-By-Sequencing (GBS) represents a simple, cost-effective, and highly multiplexed alternative for species with or without an available reference genome. However, this technology requires specific optimization for each species, especially for the restriction enzyme (RE) used. Here we report on the application of GBS in a test experiment with 18 genotypes of wild and domesticated Phaseolus vulgaris. After an in silico digestion with different RE of the P. vulgaris genome reference sequence, we selected CviAII as the most suitable RE for GBS in common bean based on the high frequency and even distribution of restriction sites. A total of 44,875 SNPs, 1,940 deletions and 1,693 insertions were identified, with 50% of the variants located in genic sequences and tagging 11,027 genes. SNPs and InDels distribution was positively correlated with gene density across the genome. In addition, we were able to also identify putative copy number variations (CNVs) of genomic segments between different genotypes. In conclusion, GBS with the CviAII enzyme results in thousands of evenly spaced markers and provides a reliable, highthroughput and cost-effective approach for genotyping both wild and domesticated common beans.

Plant Aaquaporins are a large and diverse family of water channel proteins that are essential for several physiological processes in living organisms. in all living organisms. In plants, this family has the highest diversity of protein isoforms and substrate specificities compared to animals and bacteria. Numerous studies have linked plant aquaporins with a plethora of processes, such as nutrient acquisition, CO 2 transport, plant growth and development, and response to abiotic stresses.However, little is knowns about this protein family in common bean. Here, we present a genomewide identification of the aquaporin gene family in common bean (Phaseolus vulgaris L.), a legume crop essential for human nutrition. We identified 41 full-length coding aquaporin sequences in the common bean genome, divided by phylogenetic analysis into five sub-families (PIPs, TIPs, NIPs, SIPs and XIPs). Residues determining substrate specificity of aquaporins (i.e., NPA motifs and ar/R selectivity filter) seem conserved between common bean and other plant species, allowing inference of substrate specificity for these proteins. Thanks to the availability of RNA-sequencing datasets, expression levels in different organs and in leaves of wild and domesticated bean accessions were evaluated. Three aquaporins (PvTIP1;1, PvPIP2;4 and PvPIP1;2) have the overall highest mean expressions, with PvTIP1;1 having the highest expression among all aquaporins. We performed an EST database mining to identify drought responsive aquaporins in common bean. This analysis showed a significant increase in expression for PvTIP1;1 in drought stress conditions compared to well-watered environments. The pivotal role suggested for PvTIP1;1 in regulating water homeostasis and drought stress response in the common bean, should be verified by further field experimentation under drought stress.

BackgroundWild crop relatives have been potentially subjected to stresses on an evolutionary time scale prior to domestication. Among these stresses, drought is one of the main factors limiting crop productivity and its impact is likely to increase under current scenarios of global climate change. We sought to determine to what extent wild common bean (Phaseolus vulgaris) exhibited adaptation to drought stress, whether this potential adaptation is dependent on the climatic conditions of the location of origin of individual populations, and to what extent domesticated common bean reflects potential drought adaptation.MethodsAn extensive and diverse set of wild beans from across Mesoamerica, along with a set of reference Mesoamerican domesticated cultivars, were evaluated for root and shoot traits related to drought adaptation. A water deficit experiment was conducted by growing each genotype in a long transparent tube in greenhouse conditions so that root growth, in addition to shoot growth, could be monitored.ResultsPhenotypic and landscape genomic analyses, based on single-nucleotide polymorphisms, suggested that beans originating from central and north-west Mexico and Oaxaca, in the driest parts of their distribution, produced more biomass and were deeper-rooted. Nevertheless, deeper rooting was correlated with less root biomass production relative to total biomass. Compared with wild types, domesticated types showed a stronger reduction and delay in growth and development in response to drought stress. Specific genomic regions were associated with root depth, biomass productivity and drought response, some of which showed signals of selection and were previously related to productivity and drought tolerance.ConclusionsThe drought tolerance of wild beans consists in its stronger ability, compared with domesticated types, to continue growth in spite of water-limited conditions. This study is the first to relate bean response to drought to environment of origin for a diverse selection of wild beans. It provides information that needs to be corroborated in crosses between wild and domesticated beans to make it applicable to breeding programmes.

Lima bean (Phaseolus lunatus L.), one of the five domesticated Phaseolus bean crops, shows a wide range of ecological adaptations along its distribution range from Mexico to Argentina. These adaptations make it a promising crop for improving food security under predicted scenarios of climate change in Latin America and elsewhere. In this work, we combine long and short read sequencing technologies with a dense genetic map from a biparental population to obtain the chromosome-level genome assembly for Lima bean. Annotation of 28,326 gene models show high diversity among 1917 genes with conserved domains related to disease resistance. Structural comparison across 22,180 orthologs with common bean reveals high genome synteny and five large intrachromosomal rearrangements. Population genomic analyses show that wild Lima bean is organized into six clusters with mostly non-overlapping distributions and that Mesomerican landraces can be further subdivided into three subclusters. RNA-seq data reveal 4275 differentially expressed genes, which can be related to pod dehiscence and seed development. We expect the resources presented here to serve as a solid basis to achieve a comprehensive view of the degree of convergent evolution of Phaseolus species under domestication and provide tools and information for breeding for climate change resiliency.

Lima bean (Phaseolus lunatus L.) is one of the five domesticated Phaseolus bean crops, which are essential sources of dietary proteins for human consumption. Compared to common bean (P. vulgaris), it shows a wider range of ecological adaptations along its distribution range from Mexico to Argentina. These adaptations and its phenotypic plasticity make Lima bean a promising crop for improving food security under predicted scenarios of climate change in Latin America and elsewhere. Lima bean is also an excellent model to study convergent evolution of the adaptive domestication syndrome due to its dual domestication in Mesoamerica and the Andes. Combining long and short read sequencing technologies with a dense genetic map from a biparental population, we obtained the first chromosome-level genome assembly for Lima bean. Annotation of 28,326 gene models showed high diversity among 1,917 genes with conserved domains related to disease resistance. Structural comparison across 21,180 orthologs with common bean revealed high genome synteny and two large intrachromosomal rearrangements. Speciation between P. lunatus and P. vulgaris occurred about six million years ago according to nucleotide evolution between these orthologs. Population genomic analysis of GBS data for 482 wild and domesticated accessions from the Mesoamerican and Andean gene pools provided novel evidence on population structure at a finer geographical scale. Results show that wild Lima bean is organized into six clusters with mostly non-overlapping distributions and that Mesomerican landraces can be further subdivided into three subclusters. A new wild cluster of diversity was found in the Colombian Andes and a separate genetic cluster was observed for Mesoamerican landraces of the Peninsula of Yucatan in Mexico. This study also documents genome wide patterns of selection and haplotype introgression events among gene pools. Analysis of RNA-seq data obtained from wild and domesticated accessions at two different pod developmental stages revealed 4,275 differentially expressed genes, which could be related to pod dehiscence and seed development. We expect that the present resources serve as a solid basis to achieve a comprehensive view of the degree of convergent evolution of Phaseolus species under domestication and provide new tools and information for breeding for climate change resiliency of different domesticated species.

Populus x canadensis clone I-214 exhibits a general indicator phenotype in response to excess Zn, and a higher metal uptake in roots than in shoots with a reduced translocation to aerial parts under hydroponic conditions. This physiological adaptation seems mainly regulated by roots, although the molecular mechanisms that underlie these processes are still poorly understood. Here, differential expression analysis using RNA-sequencing technology was used to identify the molecular mechanisms involved in the response to excess Zn in root. In order to maximize specificity of detection of differentially expressed (DE) genes, we consider the intersection of genes identified by three distinct statistical approaches (61 up- and 19 down-regulated) and validate them by RT-qPCR, yielding an agreement of 93% between the two experimental techniques. Gene Ontology (GO) terms related to oxidation-reduction processes, transport and cellular iron ion homeostasis were enriched among DE genes, highlighting the importance of metal homeostasis in adaptation to excess Zn by P. x canadensis clone I-214. We identified the up-regulation of two Populus metal transporters (ZIP2 and NRAMP1) probably involved in metal uptake, and the down-regulation of a NAS4 gene involved in metal translocation. We identified also four Fe-homeostasis transcription factors (two bHLH38 genes, FIT and BTS) that were differentially expressed, probably for reducing Zn-induced Fe-deficiency. In particular, we suggest that the down-regulation of FIT transcription factor could be a mechanism to cope with Zn-induced Fe-deficiency in Populus. These results provide insight into the molecular mechanisms involved in adaption to excess Zn in Populus spp., but could also constitute a starting point for the identification and characterization of molecular markers or biotechnological targets for possible improvement of phytoremediation performances of poplar trees.

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