Epigenetics: possible applications in climate-smart crop breeding

To better adapt transiently or lastingly to stimuli from the surrounding environment, the chromatin states in plant cells vary to allow the cells to fine-tune their transcriptional profiles. Modifications of chromatin states involve a wide range of post-transcriptional histone modifications, histone variants, DNA methylation, and activity of non-coding RNAs, which can epigenetically determine specific transcriptional outputs. Recent advances in the area of '-omics' of major crops have facilitated identification of epigenetic marks and their effect on plant response to environmental stresses. As most epigenetic mechanisms are known from studies in model plants, we summarize in this review recent epigenetic studies that may be important for improvement of crop adaptation and resilience to environmental changes, ultimately leading to the generation of stable climate-smart crops. This has paved the way for exploitation of epigenetic variation in crop breeding

Ancestral QTL Alleles from Wild Emmer Wheat Enhance Root Development under Drought in Modern Wheat

A near-isogenic line (NIL-7A-B-2), introgressed with a quantitative trait locus (QTL) on chromosome 7AS from wild emmer wheat (Triticum turgidum ssp. dicoccoides) into the background of bread wheat (T. aestivum L.) cv. BarNir, was recently developed and studied in our lab. NIL-7A-B-2 exhibited better productivity and photosynthetic capacity than its recurrent parent across a range of environments. Here we tested the hypothesis that root-system modifications play a major role in NIL-7A-B-2’s agronomical superiority. Root-system architecture (dry matter and projected surface area) and shoot parameters of NIL-7A-B-2 and ‘BarNir’ were evaluated at 40, 62, and 82 days after planting (DAP) in a sand-tube experiment, and root tip number was assessed in a ‘cigar-roll’ seedling experiment, both under well-watered and water-limited (WL) treatments. At 82 DAP, under WL treatment, NIL-7A-B-2 presented greater investment in deep roots (depth 40–100 cm) than ‘BarNir,’ with the most pronounced effect recorded in the 60–80 cm soil depth (60 and 40% increase for root dry matter and surface area, respectively). NIL-7A-B-2 had significantly higher root-tip numbers (∼48%) per plant than ‘BarNir’ under both treatments. These results suggest that the introgression of 7AS QTL from wild emmer wheat induced a deeper root system under progressive water stress, which may enhance abiotic stress resistance and productivity of domesticated wheat

Mapping of the eibi1 gene responsible for the drought hypersensitive cuticle in wild barley (Hordeum spontaneum)

Segregation analysis showed that eibi1, a drought hypersensitive Cuticle wild barley mutant, was monogenic and recessive, and mapped in two F, Populations, one made from a cross between the mutant and a Cultivated barley (cv. Morex), and the other between the mutant and another wild barley. A microsatellite marker screen showed that the gene was located oil barley chromosome 3H, and a set of markers already assigned to this chromosome, including both microsatellites and ESTs, was used to construct a genetic map. eibi1 co-segregated with barley EST AV918546, and was located to bin 6. The synteny between barley and rice ill this region is incomplete, with a large discrepancy in map distances, and the presence Of Multiple inversions

Exploitation of epigenetic variation of crop wild relatives for crop improvement and agrobiodiversity preservation

Crop wild relatives (CWRs) are recognized as the best potential source of traits for crop improvement. However, successful crop improvement using CWR relies on identifying variation in genes controlling desired traits in plant germplasms and subsequently incorporating them into cultivars. Epigenetic diversity may provide an additional layer of variation within CWR and can contribute novel epialleles for key traits for crop improvement. There is emerging evidence that epigenetic variants of functional and/or agronomic importance exist in CWR gene pools. This provides a rationale for the conservation of epigenotypes of interest, thus contributing to agrobiodiversity preservation through conservation and (epi)genetic monitoring. Concepts and techniques of classical and modern breeding should consider integrating recent progress in epigenetics, initially by identifying their association with phenotypic variations and then by assessing their heritability and stability in subsequent generations. New tools available for epigenomic analysis ofer the opportunity to capture epigenetic variation and integrate it into advanced (epi)breeding programmes. Advances in -omics have provided new insights into the sources and inheritance of epigenetic variation and enabled the efcient introduction of epi-traits from CWR into crops using epigenetic molecular markers, such as epiQTLs

Chromatin dynamics during interphase and cell division:similarities and differences between model and crop plants

Genetic information in the cell nucleus controls organismal development, responses to the environment and finally ensures own transmission to the next generations. To achieve so many different tasks, the genetic information is associated with structural and regulatory proteins, which orchestrate nuclear functions in time and space. Furthermore, plant life strategies require chromatin plasticity to allow a rapid adaptation to abiotic and biotic stresses. Here, we summarize current knowledge on the organisation of plant chromatin and dynamics of chromosomes during interphase and mitotic and meiotic cell divisions for model and crop plants differing as to the genome size, ploidy and amount of genomic resources available. The existing data indicate that chromatin changes accompany most (if not all) cellular processes and that there are both shared and unique themes in the chromatin structure and global chromosome dynamics among species. Ongoing efforts to understand the molecular mechanisms involved in chromatin organisation and remodeling have, together with the latest genome editing tools, potential to unlock crop genomes for innovative breeding strategies and improvements of various traits

Distribution and haplotype diversity of WKS resistance genes in wild emmer wheat natural populations.

Key messageThe wheat stripe rust resistance gene Yr36 ( WKS1 ) with a unique kinase-START domain architecture is highly conserved in wild emmer wheat natural populations. Wild emmer wheat (Triticum dicoccoides) populations have developed various resistance strategies against the stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst). The wild emmer gene, Yr36 (WKS1), which confers partial resistance to a broad spectrum of Pst races, is composed of a kinase and a START lipid-binding domain, a unique gene architecture found only in the Triticeae tribe. The analysis of 435 wild emmer accessions from a broad range of natural habitats revealed that WKS1 and its paralogue WKS2 are present only in the southern distribution range of wild emmer in the Fertile Crescent, supporting the idea that wheat domestication occurred in the northern populations. An analysis of full-length WKS1 sequence from 54 accessions identified 15 different haplotypes and very low-nucleotide diversity (π = 0.00019). The high level of WKS1 sequence conservation among wild emmer populations is in contrast to the high level of diversity previously observed in NB-LRR genes (e.g., Lr10 and Pm3). This phenomenon may reflect the different resistance mechanisms and different evolutionary pathways that shaped these genes, and may shed light on the evolution of genes that confer partial resistance to stripe rust. Only five WKS1 coding sequence haplotypes were revealed among all tested accessions, encoding four different putative WKS1 proteins (designated P0, P1, P2, and P3). Infection tests showed that P0, P1, and P3 haplotypes display a resistance response, while P2 displayed a susceptible response. These results show that the WKS1 proteins (P0, P1, and P3) can be useful to improve wheat resistance to stripe rust

Transcriptome profiling of wheat glumes in wild emmer, hulled landraces and modern cultivars

Background: Wheat domestication is considered as one of the most important events in the development of human civilization. Wheat spikelets have undergone significant changes during evolution under domestication, resulting in soft glumes and larger kernels that are released easily upon threshing. Our main goal was to explore changes in transcriptome expression in glumes that accompanied wheat evolution under domestication. Methods A total of six tetraploid wheat accessions were selected for transcriptome profiling based on their rachis brittleness and glumes toughness. RNA pools from glumes of the central spikelet at heading time were used to construct cDNA libraries for sequencing. The trimmed reads from each library were separately aligned to the reference sub-genomes A and B, which were extracted from wheat survey sequence. Differentially expression analysis and functional annotation were performed between wild and domesticated wheat, to identity candidate genes associated with evolution under domestication. Selected candidate genes were validated using real time PCR. Results Transcriptome profiles of wild emmer wheat, wheat landraces, and wheat cultivars were compared using next generation sequencing (RNA-seq). We have found a total of 194,893 transcripts, of which 73,150 were shared between wild, landraces, and cultivars. From 781 differentially expressed genes (DEGs), 336 were down-regulated and 445 were up-regulated in the domesticated compared to wild wheat genotypes. Gene Ontology (GO) annotation assigned 293 DEGs (37.5 %) to GO term groups, of which 134 (17.1 %) were down-regulated and 159 (20.4 %) up-regulated in the domesticated wheat. Some of the down-regulated DEGs in domesticated wheat are related to the biosynthetic pathways that eventually define the mechanical strength of the glumes, such as cell wall, lignin, pectin and wax biosynthesis. The reduction in gene expression of such genes, may explain the softness of the glumes in the domesticated forms. In addition, we have identified genes involved in nutrient remobilization that may affect grain size and other agronomic traits evolved under domestication. Conclusions The comparison of RNA-seq profiles between glumes of wheat groups differing in glumes toughness and rachis brittleness revealed a few DEGs that may be involved in glumes toughness and nutrient remobilization. These genes may be involved in processes of wheat improvement under domestication.Science, Faculty ofNon UBCBotany, Department ofReviewedFacult

Variation in phosphorus and sulfur content shapes the genetic architecture and phenotypic associations within the wheat grain ionome

Dissection of the genetic basis of wheat ionome is crucial for understanding the physiological and biochemical processes underlying mineral accumulation in seeds, as well as for efficient crop breeding. Most of the elements essential for plants are metals stored in seeds as chelate complexes with phytic acid or sulfur-containing compounds. We assume that the involvement of phosphorus and sulfur in metal chelation is the reason for strong phenotypic correlations within ionome. Adjustment of element concentrations for the effect of variation in phosphorus and sulfur seed content resulted in drastic change of phenotypic correlations between the elements. The genetic architecture of wheat grain ionome was characterized by quantitative trait loci (QTL) analysis using a cross between durum and wild emmer wheat. QTL analysis of the adjusted traits and two-trait analysis of the initial traits paired with either P or S considerably improved QTL detection power and accuracy, resulting in the identification of 105 QTLs and 617 QTL effects for 11 elements. Candidate gene search revealed some potential functional associations between QTLs and corresponding genes within their intervals. Thus, we have shown that accounting for variation in P and S is crucial for understanding of the physiological and genetic regulation of mineral composition of wheat grain ionome and can be implemented for other plants