A chromosome-scale genome assembly of Hordeum erectifolium: genomic, transcriptomic and anatomical adaptations to drought in a wild barley relative

Abstract

Wild crop relatives are valuable genetic resources for improving stress adaptation in culti vated 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 species for stress-adaptation research. Weassembled a chromosome-scale, annotated reference genome of H. erectifolium com prising 3.85 Gbp, and identified 71 475 genes supported by a tissue-specific gene expression atlas. Comparative morphological, physiological and transcriptomic analyses under water lim itation were conducted with H. erectifolium, and cultivated and wild barley. Hordeum erectifolium displayed a greater density of leaf veins and sclerenchyma cells, alongside rapid leaf rolling upon dehydration. Genomic comparisons revealed structural varia tions, 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 stra tegies: metabolic downregulation and survival prioritization in H. erectifolium vs maintenance of metabolic activity and competitiveness in barley. Our data suggest that H. erectifolium is genetically primed for survival under drought through anatomical adaptations, gene family expansion,