Wheat Domestication Research Articles

Natural alleles of LEAFY and WAPO1 interact to regulate spikelet number per spike in wheat

Key messageSpecific combinations ofLFY andWAPO1 natural alleles maximize spikelet number per spike in wheat. Spikelet number per spike (SNS) is an important yield component in wheat that determines the maximum number of grains that can be formed in a wheat spike. In wheat, loss-of-function mutations in LEAFY (LFY) or its interacting protein WHEAT ORTHOLOG OF APO1 (WAPO1) significantly reduce SNS by reducing the rate of formation of spikelet meristems. In previous studies, we identified a natural amino acid change in WAPO1 (C47F) that significantly increases SNS in hexaploid wheat. In this study, we searched for natural variants in LFY that were associated with differences in SNS and detected significant effects in the LFY-B region in a nested association mapping population. We generated a large mapping population and confirmed that the LFY-B polymorphism R80S is linked with the differences in SNS, suggesting that LFY-B is the likely causal gene. A haplotype analysis revealed two amino acid changes P34L and R80S, which were both enriched during wheat domestication and breeding suggesting positive selection. We also explored the interactions between the LFY and WAPO1 natural variants for SNS using biparental populations and identified significant interaction, in which the positive effect of the 80S and 34L alleles from LFY-B was only detected in the WAPO-A1 47F background but not in the 47C background. Based on these results, we propose that the allele combination WAPO-A1-47F/LFY-B 34L 80S can be used in wheat breeding programs to maximize SNS and increase grain yield potential in wheat.

Genome-wide identification of m6A-related gene family and the involvement of TdFIP37 in salt stress in wild emmer wheat.

The genomic organization, phylogenetic relationship, expression patterns, and genetic variations of m6A-related genes were systematically investigated in wild emmer wheat and the function of TdFIP37 regulating salt tolerance was preliminarily determined. m6A modification is one of the most abundant and crucial RNA modifications in eukaryotics, playing the indispensable role in growth and development as well as stress response in plants. However, its significance in wild emmer wheat remains elusive. Here, a genome-wide search of m6A-related genes was conducted in wild emmer wheat to obtain 64 candidates, including 21 writers, 17 erasers, and 26 readers. Phylogenetic and collinearity analysis demonstrated that segmental duplication and polyploidization contributed mainly to the expansion of m6A-related genes in wild emmer. A number of cis-acting elements involving in stress and hormonal regulation were found in the promoter regions of them, such as MBS, LTR, and ABRE. Genetic variation of them was also investigated using resequencing data and obvious genetic bottleneck was occurred on them during wild emmer wheat domestication process. Furthermore, the salt-responsive candidates were investigated through RNA-seq data and qRT-PCR validation using the salt-tolerant and -sensitive genotypes and the co-expression analysis showed that they played the hub role in regulating salt stress response. Finally, the loss-function mutant of Tdfip37 displayed the significantly higher salt-sensitive compared to WT and then RNA-seq analysis demonstrated that FIP37 mediated the MAPK pathway, hormone signal transduction, as well as transcription factor to regulate salt tolerance. This study provided the potential m6A genes for functional analysis, which will contribute to better understand the regulatory roles of m6A modification and also improve the salt tolerance from the perspective of epigenetic approach in emmer wheat and other crops.

Transcriptomic response to nitrogen availability reveals signatures of adaptive plasticity during tetraploid wheat domestication.

The domestication of crops, coupled with agroecosystem development, is associated with major environmental changes and provides an ideal model of phenotypic plasticity. Here, we examined 32 genotypes of three tetraploid wheat (Triticum turgidum L.) subspecies, wild emmer, emmer, and durum wheat, which are representative of the key stages in the domestication of tetraploid wheat. We developed a pipeline that integrates RNA-Seq data and population genomics to assess gene expression plasticity and identify selection signatures under diverse nitrogen availability conditions. Our analysis revealed differing gene expression responses to nitrogen availability across primary (wild emmer to emmer) and secondary (emmer to durum wheat) domestication. Notably, nitrogen triggered the expression of twice as many genes in durum wheat compared to that in emmer and wild emmer. Unique selection signatures were identified at each stage: primary domestication mainly influenced genes related to biotic interactions, whereas secondary domestication affected genes related to amino acid metabolism, in particular lysine. Selection signatures were found in differentially expressed genes (DEGs), notably those associated with nitrogen metabolism, such as the gene encoding glutamate dehydrogenase (GDH). Overall, our study highlights the pivotal role of nitrogen availability in the domestication and adaptive responses of a major food crop, with varying effects across different traits and growth conditions.

Wheat domestication alters root metabolic functions to drive the assembly of endophytic bacteria.

The domestication process progressively differentiated wild relatives from modern cultivars, thus impacting plant-associated microorganisms. Endophytic bacterial communities play vital roles in plant growth, development, and health, which contribute to the crop's sustainable development. However, how plant domestication impacts endophytic bacterial communities and relevant root exudates in wheat remains unclear. First, we have observed that the domestication process increased the root endophytic microbial community diversity of wheat while decreasing functional diversity. Second, domestication decreased the endophytic bacterial co-occurrence network stability, and it did significantly alter the abundances of core microorganisms or potential probiotics. Third, untargeted LC-MS metabolomics revealed that domestication significantly altered the metabolite profiles, and the abundances of various root exudates released were significantly correlated with keystone taxa including the Chryseobacterium, Massilia, and Lechevalieria. Moreover, we found that root exudates, especially L-tyrosine promote the growth of plant-beneficial bacteria, such as Chryseobacterium. Additionally, with L-tyrosine and Chryseobacterium colonized in the roots, the growth of wild wheat's roots was significantly promoted, while no notable effect could be found in the domesticated cultivars. Overall, this study suggested that wild wheat as a key germplasm material, and its native endophytic microbes may serve as a resource for engineering crop microbiomes to improve the morphological and physiological traits of crops in widely distributed poor soils.

Current research status and emerging trends in wheat: An integrated scientometric analysis based on ploidy uncovers hidden footprints in the scientific landscape

Wheat, a highly versatile staple crop cultivated extensively for its grains on a global scale, is poised to experience increased demand to sustain the burgeoning population, owing to its superior nutritional potential. Modern wheat, a hexaploid species, has evolved through the introgression of numerous preceding ploidies, including Einkorn, Emmer, Aegilops, and others, each possessing distinct qualitative and quantitative traits. Scientometric and topical analyses serve as effective tools to quantitatively evaluate scientific research by measuring the knowledge expressed in scientific publications and keywords. Thus, comprehending the research status regarding wheat domestication events within primary, secondary, and tertiary gene pools is paramount for enhancing wheat production. In this study, we analyze data retrieved from PubMed to elucidate the research status and identify bottlenecks across different ploidy of genomic pools of wheat. The publication trends on wheat have experienced exponential growth over the past three decades, with China emerging as a leading center for publications. In contrast to the publication frequency observed in hexaploid common wheat, scholarly output concerning Einkorn and Aegilops is approximately tenfold lesser, with emmer trailing behind at three times fewer publications. This discrepancy underscores the prioritization of expedited research initiatives targeting these species, aimed at elucidating latent biological characteristics and optimizing their breeding capabilities. Keywords such as “stress,” “GWAS,” and “gene” are prominent, reflecting the challenges posed by climatic factors on wheat production and their mitigation through molecular breeding and gene manipulation. Notably, the keyword “einkorn” highlights its potential as a donor for fine-tuning traits related to wheat adaptation processes and quality, crucial for modern wheat’s survivability under adverse climates. Conversely, higher publication rates on emmer are primarily associated with Italy, possibly due to its favorable Mediterranean climate for tetraploid wheat. Keywords like “Pasta” and “Ochratoxin, DON” are prevalent, with the former being derived from durum wheat and the latter being reported in higher amounts in durum compared to other wheat species, rendering it less suitable for consumption. Enriched keywords such as “genome” and “resistance” underscore the critical characteristics of Aegilops. Other significant keywords like “Aceria tosichella” possibly indicate multiple stages of resistance conferred by Aegilops, while the presence of the grain softness protein “puroindoline” enhances its acceptability for donation by Aegilops. Spelt, a close relative of common wheat, exhibits a research trend with thousands of annual publications and enriched keywords such as “stress” and “yield” reflect the current scientific emphasis on wheat research. Furthermore, hierarchical keywords like “bio-control” and “celiac disease” merit consideration for future research on hexaploid wheat.

GeCKO: user-friendly workflows for genotyping complex genomes using target enrichment capture. A use case on the large tetraploid durum wheat genome

BackgroundGenotyping of individuals plays a pivotal role in various biological analyses, with technology choice influenced by multiple factors including genomic constraints, number of targeted loci and individuals, cost considerations, and the ease of sample preparation and data processing. Target enrichment capture of specific polymorphic regions has emerged as a flexible and cost-effective genomic reduction method for genotyping, especially adapted to the case of very large genomes. However, this approach necessitates complex bioinformatics treatment to extract genotyping data from raw reads. Existing workflows predominantly cater to phylogenetic inference, leaving a gap in user-friendly tools for genotyping analysis based on capture methods. In response to these challenges, we have developed GeCKO (Genotyping Complexity Knocked-Out). To assess the effectiveness of combining target enrichment capture with GeCKO, we conducted a case study on durum wheat domestication history, involving sequencing, processing, and analyzing variants in four relevant durum wheat groups.ResultsGeCKO encompasses four distinct workflows, each designed for specific steps of genomic data processing: (i) read demultiplexing and trimming for data cleaning, (ii) read mapping to align sequences to a reference genome, (iii) variant calling to identify genetic variants, and (iv) variant filtering. Each workflow in GeCKO can be easily configured and is executable across diverse computational environments. The workflows generate comprehensive HTML reports including key summary statistics and illustrative graphs, ensuring traceable, reproducible results and facilitating straightforward quality assessment. A specific innovation within GeCKO is its 'targeted remapping' feature, specifically designed for efficient treatment of targeted enrichment capture data. This process consists of extracting reads mapped to the targeted regions, constructing a smaller sub-reference genome, and remapping the reads to this sub-reference, thereby enhancing the efficiency of subsequent steps.ConclusionsThe case study results showed the expected intra-group diversity and inter-group differentiation levels, confirming the method's effectiveness for genotyping and analyzing genetic diversity in species with complex genomes. GeCKO streamlined the data processing, significantly improving computational performance and efficiency. The targeted remapping enabled straightforward SNP calling in durum wheat, a task otherwise complicated by the species' large genome size. This illustrates its potential applications in various biological research contexts.

Transcriptome variations in hybrids of wild emmer wheat (Triticum turgidum ssp. dicoccoides)

BackgroundWild emmer wheat is a great candidate to revitalize domesticated wheat genetic diversity. Recent years have seen intensive investigation into the evolution and domestication of wild emmer wheat, including whole-genome DNA and transcriptome sequencing. However, the impact of intraspecific hybridization on the transcriptome of wild emmer wheat has been poorly studied. In this study, we assessed changes in methylation patterns and transcriptomic variations in two accessions of wild emmer wheat collected from two marginal populations, Mt. Hermon and Mt. Amasa, and in their stable F4 hybrid.ResultsMethylation-Sensitive Amplified Polymorphism (MSAP) detected significant cytosine demethylation in F4 hybrids vs. parental lines, suggesting potential transcriptome variation. After a detailed analysis, we examined nine RNA-Seq samples, which included three biological replicates from the F4 hybrid and its parental lines. RNA-Seq databases contained approximately 200 million reads, with each library consisting of 15 to 25 million reads. There are a total of 62,490 well-annotated genes in these databases, with 6,602 genes showing differential expression between F4 hybrid and parental lines Mt. Hermon and Mt. Amasa. The differentially expressed genes were classified into four main categories based on their expression patterns. Gene ontology (GO) analysis revealed that differentially expressed genes are associated with DNA/RNA metabolism, photosynthesis, stress response, phosphorylation and developmental processes.ConclusionThis study highlights the significant transcriptomic changes resulting from intraspecific hybridization within natural plant populations, which might aid the nascent hybrid in adapting to various environmental conditions.

Q negatively regulates wheat salt tolerance through directly repressing the expression of TaSOS1 and reactive oxygen species scavenging genes.

The Q transcription factor plays important roles in improving multiple wheat domestication traits such as spike architecture, threshability and rachis fragility. However, whether and how it regulates abiotic stress adaptation remain unclear. We found that the transcriptional expression of Q can be induced by NaCl and abscisic acid treatments. Using the q mutants generated by CRISPR/Cas9 and Q overexpression transgenic lines, we showed that the domesticated Q gene causes a penalty in wheat salt tolerance. Then, we demonstrated that Q directly represses the transcription of TaSOS1-3B and reactive oxygen species (ROS) scavenging genes to regulate Na+ and ROS homeostasis in wheat. Furthermore, we showed that wheat salt tolerance protein TaWD40 interacts with Q to competitively interfere with the interaction between Q and the transcriptional co-repressor TaTPL. Taken together, our findings reveal that Q directly represses the expression of TaSOS1 and some ROS scavenging genes, thus causing a harmful effect on wheat salt tolerance.

Map-based cloning and characterization reveal that an R2R3 MYB gene confers red glume in wheat

Pigment accumulation is an important trait related to wheat domestication, but there remains a limited understanding of its molecular mechanism. The genetic control of the red glume trait by a dominant allele, Rg-B1, on 1BS was reported in the last century, but the underlying gene and its molecular basis remained elusive. Here, we identified TraesTSP1B01G005700 (G57) encoding an R2R3-MYB transcription factor (TF) as the candidate Rg-B1 gene controlling red glume color by a combination of genome-wide association study (GWAS), bulked segregant RNA-sequencing (BSR-Seq), map-based cloning, and RNA-seq. TheRg-B1locus had zero to five duplicate copies only one of whichhadhightranscriptional activity. Genetic evidence suggested that promoter sequence variation in G57 in the glumes leads to high expression of G57, resulting in the red glume phenotype. G57 could bind to the promoters of anthocyanin synthesis genes TaCHS, TaF3ʹH, and TaUFGT, activating their expression and contributing to anthocyanin accumulation in wheat glume. G57 also played a pivotal role in up-regulating expression of genes TaDREB1C and TaFLO2 associated with increased grain weight, thereby causing increased grain weight. Our research offers a better understanding of the molecular basis of red glume in bread wheat.

Diversification of quantitative morphological traits in wheat.

The development and morphology of crop plants have been profoundly altered by evolution under cultivation, initially through unconscious selection, without deliberate foresight, and later by directed breeding. Wild wheats remain an important potential source of variation for modern breeders; however, the sequence and timing of morphological changes during domestication are not fully resolved. We grew and measured 142 wheat accessions representing different stages in wheat evolution, including three independent domestication events, and compared their morphological traits to define the morphospace of each group. The results show that wild and domesticated wheats have overlapping morphospaces, but each also occupies a distinct area of morphospace from one another. Polyploid formation in wheat increased leaf biomass and seed weight but had its largest effects on tiller loss. Domestication continued to increase the sizes of wheat leaves and seeds and made wheat grow taller, with more erect architecture. Associated changes to the biomass of domesticated wheats generated more grains and achieved higher yields. Landrace improvement subsequently decreased the numbers of tillers and spikes, to focus resource allocation to the main stem, accompanied by a thicker main stem and larger flag leaves. During the Green Revolution, wheat height was reduced to increase the harvest index and therefore yield. Modern wheats also have more erect leaves and larger flower biomass proportions than landraces. Quantitative trait history in wheat differs by trait. Some trait values show progressive changes in the same direction (e.g. leaf size, grain weight), whereas others change in a punctuated way at particular stages (e.g. canopy architecture), and other trait values switch directions during wheat evolution (e.g. plant height, flower biomass proportion). Agronomically valued domestication traits arose during different stages of wheat history, such that modern wheats are the product of >10 000 years of morphological evolution.

Domestication caused taxonomical and functional shifts in the wheat rhizosphere microbiota, and weakened the natural bacterial biocontrol against fungal pathogens

Modern crops might have lost some of their functional traits, required for interacting with beneficial microbes, as a result of the genotypic/phenotypic modifications that occurred during domestication. Here, we studied the bacterial and fungal microbiota in the rhizosphere of two cultivated wheat species (Triticum aestivum and T. durum) and their respective ancestors (Aegilops tauschii and T. dicoccoides), in three experimental fields, by using metabarcoding of 16S rRNA genes and ITS2, coupled with co-occurrence network analysis. Moreover, the abundance of bacterial genes involved in N- and P-cycles was estimated by quantitative PCR, and urease, alkaline phosphatase and phosphomonoesterase activities were assessed by enzymatic tests. The relationships between microbiota and environmental metadata were tested by correlation analysis. The assemblage of core microbiota was affected by both site and plant species. No significant differences in the abundance of potential fungal pathogens between wild and cultivated wheat species were found; however, co-occurrence analysis showed more bacterial–fungal negative correlations in the wild species. Concerning functions, the nitrogen denitrification nirS gene was consistently more abundant in the rhizosphere of A. tauschii than T. aestivum. Urease activity was higher in the rhizosphere of each wild wheat species in at least two of the research locations. Several microbiota members, including potentially beneficial taxa such as Lysobacter and new taxa such as Blastocatellaceae, were found to be strongly correlated to rhizospheric soil metadata. Our results showed that a functional microbiome shift occurred as a result of wheat domestication. Notably, these changes also included the reduction of the natural biocontrol potential of rhizosphere-associated bacteria against pathogenic fungi, suggesting that domestication disrupted the equilibrium of plant-microbe relationships that had been established during million years of co-evolution.

Wheat cultivar replacement drives soil microbiome and microbial cooccurrence patterns

While wheat domestication is reported to influence the soil microbial community, few studies have evaluated the influence of cultivar replacement in modern breeding on both bacterial and fungal communities. Especially, few studies reported the bacterial-fungal interkingdom association by analysis of taxa co-occurrence or co-exclusion between different wheat growth stages. In this study, we selected major wheat cultivars from different decades to investigate their genetic relatedness, plant traits, soil bacterial and fungal communities in the rhizosphere and proximal root zone, and the relationships between them. Our results indicated that host selection had the greatest impact on bacterial and fungal communities compared to growth stage and sampling location (P<0.001). At flowering, the soil microbial community in the genotype group consisting of the 1950 s (W50 s) and 1960 s (W60 s) cultivars could be clearly distinguished from those in later genotype groups. Plant traits explained the largest source of variation in microbial β-diversity (12.8–20.6%) (P=0.01), with plant height, aboveground dry matter, leaf area per plant and specific root length being associated with the divergence in microbial composition or quantity among cultivars. The cultivar from the 1970 s (W70 s) enriched a greater number of microbial taxa with the highest relative abundance, suggesting that old cultivar could be considered as a source of cultivar-microbe interaction. The cultivar from the 2000 s (W00 s) enriched taxa from the bacterial genus Nocardioides and increased the fungal phylum Glomeromycota in the rhizosphere. At three growth stages, W00 s root-zone exhibited the highest bacteria/fungi ratio (B/F) and contained more phosphorus cycle-related bacterial phoD-genes than W50 s and W60 s. The co-occurrence network revealed more operational taxonomic units (OTUs) from the bacterial order Rhizobiales in the largest module of W00 s. The increased B/F ratio and the aforementioned taxa are reported to be involved in soil nitrogen and phosphorus availability, suggesting that contemporary cultivar may recruit beneficial bacteria and fungi while weaken the association with other fungi. These findings contribute to the development of microbiome-based breeding strategies for sustainable wheat farming.

Phenotyping and identification of target traits for de novo domestication of wheat wild relatives

AbstractDe novo domestication—the modification of domestication genes in crop wild relatives via genome editing—is an approach for harnessing the beneficial genetic diversity of crop wild relatives. A prerequisite for de novo domestication is phenotyping to identify genetic materials suitable for cultivation in the respective environment. Taxa from the wheat genepool (Triticum aestivum, Triticum durum, Triticum monococcum) are a staple food; these taxa comprise wild relatives of different ploidy levels. The diploid Triticum boeoticum and Triticum urartu and the tetraploid Triticum dicoccoides and Triticum araraticum harbor desirable traits such as high grain quality and abiotic and biotic stress tolerance. Hence, they are candidates for de novo domestication. Here, we grew 111 wild wheats and 38 landraces originating predominantly from the Fertile Crescent and six modern wheat cultivars in a field in Giessen, Germany, to evaluate their environmental adaptability to the central European climate and to identify potential candidates and target traits for de novo domestication. We demonstrate that several wild taxa are suitable for cultivation in the central European environment and that they have distinct characteristics that need to be modified during de novo domestication. The normalized difference vegetation index and the thermal time to heading and flowering indicated excellent adaptability of some wheat wild relatives to central European conditions. The values of yield parameters such as grain weight per plant, number of tillers, and thousand kernel weight were lower in the wild wheats than in the landraces. Therefore, these traits should be targeted for improvement during the de novo domestication of wild wheats.

Reviving grain quality in wheat through non-destructive phenotyping techniques like hyperspectral imaging.

A long-term goal of breeders and researchers is to develop crop varieties that can resist environmental stressors and produce high yields. However, prioritising yield often compromises improvement of other key traits, including grain quality, which is tedious and time-consuming to measure because of the frequent involvement of destructive phenotyping methods. Recently, non-destructive methods such as hyperspectral imaging (HSI) have gained attention in the food industry for studying wheat grain quality. HSI can quantify variations in individual grains, helping to differentiate high-quality grains from those of low quality. In this review, we discuss the reduction of wheat genetic diversity underlying grain quality traits due to modern breeding, key traits for grain quality, traditional methods for studying grain quality and the application of HSI to study grain quality traits in wheat and its scope in breeding. Our critical review of literature on wheat domestication, grain quality traits and innovative technology introduces approaches that could help improve grain quality in wheat.

Einkorn genomics reveals ancient roots of domesticated wheat

Wheat is an important staple food crop that underwent complex genome duplications. During domestication, genetic changes occurred, improving modern wheat, but understanding its phylogenetic history has beenlacking. Mahmood and Mansoor discuss a recent publication demonstrating the evolutionary history of domesticated wheat (Triticum monococcum), providing opportunities for advancements in cereal improvement.

Comparative Analysis Reveals Different Evolutionary Fates and Biological Functions in Wheat Duplicated Genes (Triticum aestivum L.).

Wheat (Triticum aestivum L.) is a staple food crop that provides 20% of total human calorie consumption. Gene duplication has been considered to play an important role in evolution by providing new genetic resources. However, the evolutionary fates and biological functions of the duplicated genes in wheat remain to be elucidated. In this study, the resulting data showed that the duplicated genes evolved faster with shorter gene lengths, higher codon usage bias, lower expression levels, and higher tissue specificity when compared to non-duplicated genes. Our analysis further revealed functions of duplicated genes in various biological processes with significant enrichment to environmental stresses. In addition, duplicated genes derived from dispersed, proximal, tandem, transposed, and whole-genome duplication differed in abundance, evolutionary rate, gene compactness, expression pattern, and genetic diversity. Tandem and proximal duplicates experienced stronger selective pressure and showed a more compact gene structure with diverse expression profiles than other duplication modes. Moreover, genes derived from different duplication modes showed an asymmetrical evolutionary pattern for wheat A, B, and D subgenomes. Several candidate duplication hotspots associated with wheat domestication or polyploidization were characterized as potential targets for wheat molecular breeding. Our comprehensive analysis revealed the evolutionary trajectory of duplicated genes and laid the foundation for future functional studies on wheat.

Einkorn genomics sheds light on history of the oldest domesticated wheat

Einkorn (Triticum monococcum) was the first domesticated wheat species, and was central to the birth of agriculture and the Neolithic Revolution in the Fertile Crescent around 10,000 years ago1,2. Here we generate and analyse 5.2-Gb genome assemblies for wild and domesticated einkorn, including completely assembled centromeres. Einkorn centromeres are highly dynamic, showing evidence of ancient and recent centromere shifts caused by structural rearrangements. Whole-genome sequencing analysis of a diversity panel uncovered the population structure and evolutionary history of einkorn, revealing complex patterns of hybridizations and introgressions after the dispersal of domesticated einkorn from the Fertile Crescent. We also show that around 1% of the modern bread wheat (Triticum aestivum) A subgenome originates from einkorn. These resources and findings highlight the history of einkorn evolution and provide a basis to accelerate the genomics-assisted improvement of einkorn and bread wheat.

Genome-Wide Identification, Expression and Evolution Analysis of m6A Writers, Readers and Erasers in Aegilops_tauschii.

N6-methyladenosine modifications (m6A) is one of the most abundant and prevalent post-transcriptional RNA modifications in plants, playing the crucial role in plant growth and development and stress adaptation. However, the m6A regulatory machinery in Aegilops_tauschii, the D genome progenitor of common wheat, is not well understood at present. Here, we systematically identified the m6A-related genes in Aegilops with a genome-wide search approach. In total, 25 putative m6A genes composed of 5 writers, 13 readers and 7 erasers were obtained. A phylogenetic analysis clearly grouped them into three subfamilies with the same subfamily showing similar gene structures and conserved domains. These m6A genes were found to contain a large number of cis-acting elements associating with plant hormones, regulation of growth and development as well as stress response, suggesting their widespread regulation function. Furthermore, the expression profiling of them was investigated using RNA-seq data to obtain stress-responsive candidates, of which 5 were further validated with a qPCR analysis. Finally, the genetic variation of m6A-related genes was investigated between Aegilops and D subgenome of wheat based on re-sequencing data, and an obvious genetic bottleneck occurred on them during the wheat domestication process. The promising haplotype association with domestication and agronomic traits was also detected. This study provided some insights on the genomic organization and evolutionary features of m6A-related genes in Aegilops, which will facilitate the further functional study and also contribute to broaden the genetic basis for genetic improvement in wheat and other crops.

Plant domestication shapes rhizosphere microbiome assembly and metabolic functions

BackgroundThe rhizosphere microbiome, which is shaped by host genotypes, root exudates, and plant domestication, is crucial for sustaining agricultural plant growth. Despite its importance, how plant domestication builds up specific rhizosphere microbiomes and metabolic functions, as well as the importance of these affected rhizobiomes and relevant root exudates in maintaining plant growth, is not well understood. Here, we firstly investigated the rhizosphere bacterial and fungal communities of domestication and wild accessions of tetraploid wheat using amplicon sequencing (16S and ITS) after 9 years of domestication process at the main production sites in China. We then explored the ecological roles of root exudation in shaping rhizosphere microbiome functions by integrating metagenomics and metabolic genomics approaches. Furthermore, we established evident linkages between root morphology traits and keystone taxa based on microbial culture and plant inoculation experiments.ResultsOur results suggested that plant rhizosphere microbiomes were co-shaped by both host genotypes and domestication status. The wheat genomes contributed more variation in the microbial diversity and composition of rhizosphere bacterial communities than fungal communities, whereas plant domestication status exerted much stronger influences on the fungal communities. In terms of microbial interkingdom association networks, domestication destabilized microbial network and depleted the abundance of keystone fungal taxa. Moreover, we found that domestication shifted the rhizosphere microbiome from slow growing and fungi dominated to fast growing and bacteria dominated, thereby resulting in a shift from fungi-dominated membership with enrichment of carbon fixation genes to bacteria-dominated membership with enrichment of carbon degradation genes. Metagenomics analyses further indicated that wild cultivars of wheat possess higher microbial function diversity than domesticated cultivars. Notably, we found that wild cultivar is able to harness rhizosphere microorganism carrying N transformation (i.e., nitrification, denitrification) and P mineralization pathway, whereas rhizobiomes carrying inorganic N fixation, organic N ammonification, and inorganic P solubilization genes are recruited by the releasing of root exudates from domesticated wheat. More importantly, our metabolite-wide association study indicated that the contrasting functional roles of root exudates and the harnessed keystone microbial taxa with different nutrient acquisition strategies jointly determined the aboveground plant phenotypes. Furthermore, we observed that although domesticated and wild wheats recruited distinct microbial taxa and relevant functions, domestication-induced recruitment of keystone taxa led to a consistent growth regulation of root regardless of wheat domestication status.ConclusionsOur results indicate that plant domestication profoundly influences rhizosphere microbiome assembly and metabolic functions and provide evidence that host plants are able to harness a differentiated ecological role of root-associated keystone microbiomes through the release of root exudates to sustain belowground multi-nutrient cycles and plant growth. These findings provide valuable insights into the mechanisms underlying plant-microbiome interactions and how to harness the rhizosphere microbiome for crop improvement in sustainable agriculture.CBzZNC2FEDswGcHctbDosaVideo

Distinctive root system adaptation of ploidy wheats to water stress: A cue to yield enhancement

AbstractGiven the worldwide effort to improve crop drought resistance, it is crucial to understand the mechanisms of root system adaptation of ploidy wheat to water‐deficient environments. A meta‐analysis was performed to examine the changes in root system mechanisms under drought conditions. Data used in the analysis were drawn from 192 papers, taking into account wheat ploidy levels as well as pot and field studies. The results illustrated that water stress reduced grain yield and aboveground biomass to a greater extent in diploid and tetraploid compared with hexaploid genotypes. In contrast, drought reduced root biomass, root surface area and root volume more in hexaploid than in diploid and tetraploid wheat. Under water‐limited conditions, diploid and tetraploid genotypes exhibited greater root biomass and root length densities in the topsoil. Hexaploid genotypes greatly reduced root biomass and root length density in the topsoil and maintained higher root biomass and root length density in subsoil. These genotypes also showed smaller root diameter and xylem centre vessel diameter under drought conditions. The analysis revealed that grain yield was negatively correlated with topsoil root biomass and root length density, root volume, root diameter and xylem centre vessel, but positively correlated with subsoil root mass, root length density and root vigour. The study demonstrated that domestication and selection pressures of ploidy wheat have altered wheat root system traits while improving grain yield. Greater root mass and root length densities in the subsoil facilitate access to soil moisture from deep layers, contributing to high yields in drought environments.