A chromosome-scale genome assembly of the pioneer plant Stylosanthes angustifolia: insights into genome evolution and drought adaptation.

Abstract

Background: Drought is a major limiting factor for plant survival and crop productivity. Stylosanthes angustifolia, a pioneer plant, exhibits remarkable drought tolerance, yet the molecular mechanisms driving its drought resistance remain largely unexplored.

Results: We present a chromosome-scale reference genome of S. angustifolia, which provides insights into its genome evolution and drought tolerance mechanisms. The assembled genome is 645.88 Mb in size, containing 319.98 Mb of repetitive sequences and 36,857 protein-coding genes. The high quality of this genome assembly is demonstrated by the presence of 99.26% BUSCO and a 19.49 long terminal repeat assembly index. Evolutionary analyses revealed that S. angustifolia shares a whole-genome duplication (WGD) event with other legumes but lacks recent WGD. Additionally, S. angustifolia has undergone gene expansion through tandem duplication approximately 12.31 million years ago. Through integrative multiomics analyses, we identified 4 gene families-namely, xanthoxin dehydrogenase, 2-hydroxyisoflavanone dehydratase, patatin-related phospholipase A, and stachyose synthetase-that underwent tandem duplication and were significantly upregulated under drought stress. These gene families contribute to the biosynthesis of abscisic acid, genistein, daidzein, jasmonic acid, and stachyose, thereby enhancing drought tolerance.

Conclusions: The genome assembly of S. angustifolia represents a significant advancement in understanding the genetic mechanisms underlying drought tolerance in this pioneer plant species. This genomic resource provides critical insights into the evolution of drought resistance and offers valuable genetic information for breeding programs aimed at improving drought resistance in crops.