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Enriched grain minerals in Aegilops tauschii-derived common wheat population under heat-stress environments.

In wheat (Triticum aestivum L.), an important source of dietary minerals, heat stress during the grain filling stage negatively affects grain yield and quality. Wheat grain mineral content has been primarily evaluated under optimum conditions; little information is available on the genetic variations and loci involved in mineral accumulation under heat stress. Therefore, this study aimed to assess the variation in 13-grain mineral concentrations and thousand kernel weight of 145 wheat multiple synthetic derivatives (MSD) genotypes harboring genes from the wild relative Aegilops tauschii Coss., evaluated under heat-stress field conditions in Sudan for two seasons, and to dissect the genomic regions associated with these mineral contents using GWAS. Our results showed sufficient variations in mineral concentrations among the MSD lines. Some MSD lines had 30-50% more minerals than the recurrent parent Norin 61. We detected 188 significant marker-trait associations (MTAs), 44 MTAs in season 2018/19, one in season 2019/20, and 143 based on BLUE. The highly significant, stable, and promising MTAs were related to Mg, Mn, P, and Ba. We identified putative candidate genes potentially involved in mineral movement (TraesCS5D03G0728800) and response to heat stress (TraesCS5D03G0723300). The findings in this study help to enhance mineral concentration and resilience in wheat under heat.

Triticum

Genome-Wide Characterization of Calmodulin-Binding Transcription Activators Genes in Aegilops tauschii.

Calcium signaling plays a central role in plant adaptation to abiotic stresses and is primarily mediated by calmodulin and its associated transcription factors. Calmodulin-binding transcription activators (CAMTAs) regulate stress-responsive gene expression, but their characteristics and functions remain largely unexplored in Aegilops tauschii Coss., the D-genome progenitor of bread wheat. In this study, a genome-wide identification and characterization of the CAMTA gene family was performed, followed by phylogenetic, structural, conserved domain, promoter cis-element, and expression analyses under drought stress. Five AetCAMTA genes were identified and classified into three phylogenetic groups. All proteins contained conserved CG-1 DNA-binding, ankyrin repeat (ANK), and IQ calmodulin-binding domains and exhibited similar exon-intron organization. Promoter analysis revealed abundant hormone- and stress-responsive cis-elements, particularly abscisic acid-responsive element (ABRE) and drought-responsive MYB-binding site (MBS) motifs, suggesting their involvement in drought-responsive signaling. Quantitative RT-PCR showed genotype- and stress-dependent expression patterns, with the drought-tolerant ecotype (TN-01-1747) exhibiting higher expression of AetCAMTA1, AetCAMTA2, and AetCAMTA3 than the drought-sensitive ecotype (TN-01-1559) under moderate drought stress. These findings provide new insights into the evolutionary and functional characteristics of AetCAMTA genes and identify promising candidates for improving drought tolerance in wheat through molecular breeding and biotechnological approaches.

Gene Expression Regulation, Plant

Properties of common wheat ferredoxin, and a comparison with ferredoxins from related species of triticum and aegilops.

Wheat ferredoxin was purified from the leaves of common wheat (Triticum aestivum). The absorption spectrum showed maxima at 465, 425, 332, and 278 nm. The absorbance ratio, A425 nm/A278 nm was 0.49, and the millimolar extinction coefficient at 425 nm was 10.8 mM-1. cm-1. The amino acid composition was determined to be Lys5, His2, Arg1, Asp11, Thr5, Ser7, Glu18, Pro5, Gly6, Ala7, Cys5, Val7, Met1, Ile4, Leu7, Tyr4, Phe1, and Trp1. The total number of amino acid residues was 97. The molecular weight was calculated from the amino acid composition to be 10,829, including iron and sulfur atoms. This value was confirmed by other methods, which were based on the contents of non-heme iron and of terminal amino acid. The N-terminal amino acid was alanine, and the C-terminal amino acid sequence was -Glu-Leu-Thr-AlaCOOH. Comparative studies were performed between T. aestivum ferredoxin and ferredoxins isolated from closely related species; these were T. aegilopoides, T. durum, Ae. squarrosa, and Ae. ovata. No significant differences in the properties of these ferredoxins were detected. It was also shown that these ferredoxins are immunologically homologous. It is, therefore, likely that one molecular species of ferredoxin is distributed through two genera of Triticum and Aegilops.

Amino Acids

Genomic introgressions from wild relatives in the wheat genome alter meiotic dynamics in inter-varietal hybrids.

The use of wild relatives to introduce original diversity in the genome of bread wheat (Triticum aestivum L.) is an interesting approach to face the challenges of sustainable agriculture and the impact of climate change on wheat production. However, the influence of these wild-species introgressions on meiosis in inter-varietal wheat hybrids remains poorly understood. We analyzed the French wheat variety Renan (Re) carrying Aegilops ventricosa (Aev)-derived 2AS/2NS and 7DL/7DvL introgressions, the reference cultivar Chinese Spring (CS), which lacks these introgressions, and their inter-varietal hybrid Chinese Spring × Renan (CSRe). This analysis combined cytogenetic approaches with the assessment of reproductive performance. Furthermore, we generated a cytological atlas of meiosis in wild tetraploid Aev, quantifying bivalent configurations and chiasma frequency. We observed a reduced pollen viability and a slight decrease in floret fertility in the hybrid CSRe. Exploration of the meiotic behavior showed that CSRe exhibited increased numbers of rod bivalents and univalents, leading to a reduced average chiasma number and frequent chromosome bridges and fragmentations, whereas the parental lines maintained stable chromosome pairing. These rearrangements indicate that homologous chromosome pairing and recombination are affected in CSRe. We applied introgression-specific oligo-Fluorescent In Situ Hybridization to localize alien segments in CSRe, providing a novel strategy to investigate the meiotic behavior of introgressed regions. The 2AS/2NS introgressed segments in CSRe were frequently located on rod bivalents or univalents, while 7DL/7DvL segments consistently formed ring bivalents. Our results provide a foundation for guiding alien gene introgression and for understanding the behavior of chromosomes with introgressions in the wheat genome.

Meiosis

Phylogeny, chromosomal mapping and expression analyses of wheat CLAVATA pathway components suggest differential selection on receptor-like kinases, CLEs and T3 WOXes.

Ensuring continuous global food security is a major challenge of the 21st century. Wheat contributes approximately 20% of the total calories consumed by humans, and an estimated 60% increase in production will be required by 2050 to meet forecast global demand. In cereals like wheat, inflorescence (ear) size and branching patterns determine the number of flowers (florets) and grains produced, and these aspects of plant architecture are regulated by the activity of stem cells in the growing shoot tips. CLAVATA peptide and receptor-like kinase signalling regulates angiosperm stem cell activity, and as changes in CLAVATA function can improve crop yields, CLAVATA is a key target for reverse engineering. Here, we identify components of the wheat CLAVATA pathway using genome searches against Triticum aestivum and its wild relatives Triticum turgidum ssp. durum, Triticum turgidum ssp. dicoccoides, Triticum urartu and Aegilops tauschii. Using phylogenetic and synteny analysis, we determine the relationship between homoeologues and infer patterns of gene family evolution. Whilst CLAVATA1, BARELY ANY MERISTEM, RECEPTOR-LIKE PROTEIN KINASE 2, CORYNE and CLAVATA2 receptor-like kinase homologues are mainly present as single genome copies as in other grasses, CLAVATA3-like but not TRACHEARY ELEMENT DIFFERENTIATION FACTOR (TDIF)-like peptide encoding genes and WUSCHEL-LIKE HOMEOBOX (WOX) genes have expanded copy numbers with many gene gains and losses during evolution. Our results highlight wheat CLAVATA pathway components for reverse genetic analysis and indicate potential differential selection on wheat receptor-like kinases, their peptide ligands and WOXes.

Triticum

Distinct evolutionary trajectories of subgenomic centromeres in polyploid wheat.

BACKGROUND: Centromeres are crucial for precise chromosome segregation and maintaining genome stability during cell division. However, their evolutionary dynamics, particularly in polyploid organisms with complex genomic architectures, remain largely enigmatic. Allopolyploid wheat, with its well-defined hierarchical ploidy series and recent polyploidization history, serves as an excellent model to explore centromere evolution. RESULTS: In this study, we perform a systematic comparative analysis of centromeres in common wheat and its corresponding ancestral species, utilizing the latest comprehensive reference genome assembly available. Our findings reveal that wheat centromeres predominantly consist of five types of centromeric-specific retrotransposon elements (CRWs), with CRW1 and CRW2 being the most prevalent. We identify distinct evolutionary trajectories in the functional centromeres of each subgenome, characterized by variations in copy number, insertion age, and CRW composition. By utilizing CENH3-ChIP data across various ploidy levels, we uncover a series of CRW invasion events that have shaped the evolution of AA subgenome centromeres. Conversely, the evolutionary process of the DD subgenome centromeres involves their expansion from diploid to hexaploid wheat, facilitating adaptation to a larger genomic context. Integration of complete einkorn centromere assemblies and Aegilops tauschii pan-genomes further revealed subgenome-specific centromere evolutionary trajectories. By inclusion of synthetic hexaploid from S2-S3 generations, alongside 2x/6 × natural accessions, we demonstrate that DD subgenome centromere expansion represents a gradual evolutionary process rather than an immediate response to polyploidization. CONCLUSIONS: Our study provides a comprehensive landscape of centromere adaptation, evolution, and maturation, along with insights into how retrotransposon invasions drive centromere evolution in polyploid wheat.

Centromere

[Identification of albumin 0.19 in wheat and other cereal proteins].

It was found that albumin 0.19, being an inhibitor of alpha-amylases from human and insect saliva, is not specific for T. aestivum and is also revealed immunochemically by means of antiserum in the proteins of T. durum. Using rocket immunoelectrophoresis, it was shown that the albumin component specific for T. aestivum is not identical to albumin 0.19. The levels of albumin 0.19 in the proteins of wheat, aegilops. secale, agropyron and barley grains were studied.

Albumins