Multi-Omics analysis provides crucial insights into ecological adaptation to dryland of a dominant grass (Psammochloa villosa, Poaceae) in Northwest China

Desertification imposes significant selective pressures on plant evolution. Psammochloa villosa, a perennial forage grass found in arid grasslands of Northwest China, exhibits exceptional drought tolerance and serves as an ideal model for studying adaptive evolution to aridity. To gain insights into the mechanisms behind this adaptation, researchers have assembled a high-quality chromosome-scale genome of P. villosa, which spans approximately 1.55 Gb of sequence data.

This assembly boasts a super-scaffold N50 value of 66.79 Mb and contains 75.84% transposable elements.

Genomic resequencing of 42 populations across the grass' major distribution revealed that P. villosa and its closest relative, Neotrinia splendens, experienced a recent whole-genome duplication (WGD) event approximately 18-20 million years ago. Following this duplication, the two species diverged around 11.2 million years ago. By reconstructing an ancestral grass karyotype (AGK) and conducting synteny analysis, the study found that both P. villosa and N. splendens underwent similar chromosomal restructuring and lineage-specific retention of numerous gene copies after the WGD event.

Further investigation demonstrated that the expanded XTH family, responsible for enzymes involved in xyloglucan endotransglucosylation and hydrolysis and thus regulating xyloglucan remodeling, showed strong transcriptional responses under PEG-6000 treatment. This suggests that the retained gene copies in P. villosa may contribute to xerophytic adaptation to arid conditions.

Overall, these findings indicate that WGD-derived gene retention created a reservoir of genetic diversity that was later shaped by desertification and environmental changes on the Qinghai-Xizang Plateau. This contributed to the formation of climate-associated genomic islands and intraspecific differentiation within P. villosa.