Biology subjects

Haraldsson, E. B.

Publications and source records attributed to Haraldsson, E. B..

7 recordsLinked to original sources

bioRxiv2026

Phylogeny, thermal seasonality, and life history shape trait variation in annual and perennial barley relatives

O_LIThere is growing interest in developing perennial cereal crops for sustainable production, yet key differences in trait syndromes between annual and perennial grasses and their influence on environmental adaptation remain poorly understood. C_LIO_LIWe measured 25 traits in 16 annual and perennial Hordeum species (45 accessions), including barley, grown over three seasons in a common garden. Using a phylogenetic framework and repeated transitions between annual and perennial forms, we (i) identified traits distinguishing these life strategies and (ii) tested how they relate to climate at the accessions origins. C_LIO_LIWild and cultivated barley are distinguished within the Hordeum clade by high growth rates and large organs, which may have predisposed wild barley to domestication. Annual and perennial accessions differed in resource allocation: annuals had higher harvest index and leaf and grain nitrogen, while perennials produced carbon-rich tissues and sustained vegetative growth. Seasonal temperature variation shaped trait syndromes: annual traits aligned with temperature in the driest quarter, reflecting selection under terminal stress, while perennial traits correlated with temperature in the wettest quarter, the main growth phase shaping long-term performance and survival. C_LIO_LIWe provide important information on traits and climate adaptations underlying perennial persistence and annual resource strategies, relevant for developing perennial cereal crops. C_LI

ecology↗

bioRxiv2025

FLOWERING LOCUS T1 is a pleiotropic regulator of reproductive development, plant longevity, and source-sink relations in barley

Source-sink interactions play a critical but mechanistically underexplored role in coordinating reproductive output and longevity in plants. Here, we investigated the role of FT1, the barley homolog of the florigen FLOWERING LOCUS T (FT), in regulating source (leaf) and sink (inflorescence) development and metabolism. Using ft1 knock-out mutants in the spring barley cultivar Golden Promise, which carries a mutated ppd-H1 allele, and in an introgression line with a wild-type Ppd-H1 allele, we show that Ppd-H1 primarily regulates the timing of inflorescence development and flowering through FT1, whereas variation in tiller number and leaf size is determined by the genetic background. ft1 mutants exhibited reduced determinacy of both leaf and inflorescence meristems, resulting in increased leaf and spikelet numbers and size, but severely reduced inflorescence fertility, altered senescence patterns, and significantly extended plant longevity. The ft1 mutants exhibited a strong transcriptional reprogramming of genes involved in both the light and dark reactions of photosynthesis in the leaf, alongside an upregulation of genes associated with carbon catabolism and stress responses in the leaf and inflorescence. Elevated soluble sugar and starch levels in ft1 inflorescences indicated that the impaired development and fertility of ft1 inflorescences were not caused by carbon limitation, but instead reflected a reduced sink strength. Our work reveals that FT1 coordinates the development of vegetative and reproductive meristems and organs with plant physiology and metabolism, thereby regulating source-sink relationships and balancing plant longevity with reproductive output.

plant biology↗

bioRxiv2025

Golden Promise-rapid, a fast-cycling barley genotype with high transformation efficiency

The spring barley cultivar Golden Promise (GP) is the major reference genotype for transformation due to its high transformability and availability of a reference genome. However, GP is characterized by a long generation cycle and stress susceptibility under non-optimal growth conditions because it carries a mutation at the floral inducer Photoperiod-H1 (Ppd-H1). Previously, we showed that a GP introgression line, Golden Promise-fast (GP-fast), generated by introducing the wild-type Ppd-H1 allele from the winter barley cultivar Igri, exhibits early flowering and improved stress resilience. In this study, we generated a fast-cycling genotype, Golden Promise-rapid (GP-rapid), isogenic to GP with high transformation efficiency. We conducted two backcrosses of GP-fast to reduce the residual Igri genome. The resulting genotype contains only a single introgression of approximately 0.6 Mbp at the Ppd-H1 locus on chromosome 2H. Under speed breeding conditions, its generation time was reduced to 63 days (25% shorter than GPs 84 days). Parallel transformation of GP, GP-fast, and GP-rapid using CRISPR/Cas9-mediated genome editing of Ppd-H1 revealed high regeneration and transformation efficiencies of GP-rapid, comparable to GP. Overall, we report on the development of a fast-cycling GP isogenic line as a research tool for efficient generation of transgenic and gene-edited barley plants. HighlightsA new fast-cycling barley genotype, GP-rapid, reduces generation time by 25% while retaining high transformation efficiency, advancing functional genomic studies in barley.

plant biology↗

bioRxiv2025

A chromosome-scale genome assembly of Hordeumerectifolium: genomic, transcriptomic and anatomicaladaptations to drought in a wild barley relative

O_LIWild crop relatives are valuable genetic resources for improving stress adaptation in cultivated species, but their effective use depends on high-quality reference genomes integrated with phenotypic and molecular datasets. Hordeum erectifolium, a wild relative of barley (H. vulgare), is adapted to intermittent and prolonged drought and saline soils, making it an excellent model for stress-adaptation research. C_LIO_LIWe assembled a chromosome-scale, annotated reference genome of H. erectifolium comprising 3.85 Gbp, and identified 71,475 genes supported by a tissue-specific gene expression atlas. Comparative morphological, physiological, and transcriptomic analyses under water limitation were conducted with cultivated and wild barley. C_LIO_LIH. erectifolium displayed a greater density of leaf veins and sclerenchyma cells, alongside rapid leaf rolling upon dehydration. Genomic comparisons revealed structural variations, independent transposon-driven evolution, and copy number expansions of desiccation-responsive gene families relative to barley. The transcriptional responses of H. erectifolium and barley to water limitation suggested contrasting drought-adaptation strategies: metabolic down-regulation and survival prioritization in H. erectifolium versus maintenance of metabolic activity and competitiveness in barley. C_LIO_LIOur data suggest that H. erectifolium is genetically primed for survival under drought through anatomical adaptations, gene family expansion, efficient shutdown of growth-related metabolism, and rapid recovery upon rehydration. C_LI

evolutionary biology↗

bioRxiv2025

Convergent life-history evolution in Hordeum: Phylogenomic insights into climatic niche variation and functional genetic differentiation among annual and perennial wild relatives of barley

Annual and perennial life-history strategies have evolved repeatedly across angiosperms, yet the genomic and environmental underpinnings of these transitions remain poorly understood, particularly in grasses. We generated de novo transcriptomes from 82 accessions representing 22 Hordeum species, including barley, and identified 257 single-copy orthologs present in all accessions to infer a robust phylogeny of the genus. By combining phylogenetic network inference with ABBA-BABA tests, we detected four cases of interspecific hybridization, three coinciding with major long-distance dispersal events across continents. Comparative climatic niche analysis indicated annual Hordeum species inhabit environments with higher temperatures, greater interannual variability, and increased human disturbance, compared to perennials, although no consistent precipitation differences were observed. Using our phylogeny as a framework, we analyzed selection and gene expression to uncover genomic changes associated with life-history strategy while accounting for phylogenetic non-independence. Additionally, we analysed gene copy number variations associated with life-history strategy. These analyses yielded 174 candidate genes across diverse biological functions, suggesting the genetic architecture underlying life-history evolution is more complex than assumed. Candidate genes grouped into six major functional categories, the most prominent being signal transduction and development, including regulators of flowering, dormancy, and meristem activity, metabolic and biosynthetic processes related to carbon allocation and storage, and stress response and defense, reflecting the resilience of perennials compared to the accelerated growth strategies of annuals. Our study reconstructs the evolutionary history and climatic niche differentiation of Hordeum species and demonstrates that convergent life-history evolution is driven by multifaceted, functionally diverse genetic mechanisms.

evolutionary biology↗

bioRxiv2024

From Flowering Time to High Temperature Resilience: PHOTOPERIOD 1 (PPD-H1) Controls Spike Fertility through Improving Stress Resistance and Energy Metabolism under High Ambient Temperatures

High ambient temperature (HT) impairs reproductive development and grain yield in temperate crops. To ensure reproductive success under HT, plants must maintain developmental stability. However, the mechanisms integrating plant development and temperature resilience are largely unknown. Here, we demonstrate that PHOTOPERIOD 1 (PPD-H1), homologous to PSEUDO RESPONSE REGULATOR genes of the Arabidopsis circadian clock, controls developmental stability in response to HT in barley. We analyzed HT responses in independent introgression lines with either the ancestral wild-type Ppd-H1 allele or the natural ppd-h1 variant, selected in spring varieties to delay flowering and enhance yield under favourable conditions. HT delayed inflorescence development and reduced grain number in ppd-h1 mutant lines, while the wild-type Ppd-H1 genotypes accelerated reproductive development and showed a stable grain set under HT. Using a CRISPR/Cas9-induced ppd-h1 mutant, we confirmed that the CCT domain of Ppd-H1 controls developmental stability, but not clock gene expression. Transcriptome and phytohormone analyses in developing leaves and inflorescences revealed increased stress gene expression and abscisic acid levels in the leaf and inflorescence of the natural and induced mutant ppd-h1 lines. Furthermore, the mutant ppd-h1 lines downregulated photosynthesis-and energy metabolism-related genes, and reduced auxin and cytokinin levels in the inflorescence, which impaired anther and pollen development. By contrast, in the wild-type Ppd-H1 plants, the transcriptome and phytohormone levels and anther and pollen development remained stable under HT. Our findings suggest that Ppd-H1 enhances stress resistance and energy metabolism, thereby stabilizing reproductive development, floret fertility and grain set under HT.

plant biology↗

bioRxiv2020

Ppd-H1 integrates drought stress signals to control spike development and flowering time in barley

Drought impairs growth and spike development and is therefore a major cause of yield losses in the temperate cereals barley and wheat. Here, we show that the photoperiod response gene PHOTOPERIOD-H1 (Ppd-H1) interacts with drought stress signals to modulate spike development. We tested the effects of a continuous mild and a transient severe drought stress on developmental timing and spike development in spring barley cultivars with a natural mutation in ppd-H1 and derived introgression lines carrying the wild-type Ppd-H1 allele from wild barley. Mild drought reduced the spikelet number and delayed floral development in spring cultivars but not the introgression lines with a wild-type Ppd-H1 allele. Similarly, drought-triggered reductions in plant height, tiller and spike number were more pronounced in the parental lines compared to the introgression lines. Transient severe stress halted growth and floral development, upon rewatering introgression lines, but not the spring cultivars, accelerated development so that control and stressed plants flowered almost simultaneously. These genetic differences in development were correlated with a differential downregulation of the flowering promotors FLOWERING LOCUS T1 and the BARLEY MADS-box genes BM3 and BM8. Our findings, therefore, demonstrate that Ppd-H1 affects developmental plasticity in response to drought in barley. HighlightWe show that Ppd-H1 integrates photoperiod and drought stress signals via FLOWERING LOCUS T 1 (FT1) and the downstream MADS-box genes BM3 and BM8 to modulate reproductive development, and shoot and spike morphology in barley.

plant biology↗