Genome and Single-Cell Transcriptome Reveal the Evolution of Holoparasitic Plants: A Case Study of Cistanche...

The Orobanchaceae family, the largest group of parasitic plants, spans a complete spectrum from autotrophic to holoparasitic species. As a typical endangered holoparasitic species within this family, Cistanche deserticola is a parasitic plant that is widely harvested for traditional medicine in desertic regions, and of growing importance as a cash crop. However, the evolution of C. deserticola at the molecular and cellular level is poorly understood. Here, we constructed the first chromosome-level genome map of C. deserticola. Comparative genomic analyses demonstrated that the C. deserticola genome exhibited a substantial loss of genes related to photosynthesis and immunity (21.58% of the total genes) and contained 115 horizontally transferred genes. This suggested that the genomic evolution of holoparasitic plants was driven by the interplay between the acquisition of functional genes and the loss of genes specific to plant tissues or functions. Additionally, parasitism-related cells were identified using a high-resolution single-cell transcriptomic atlas, revealing stage-specific differentiation during the parasitic process. Early cells (cluster 11) highly expressed dopamine/tyrosine metabolism pathways genes (e.g., polyphenol oxidase), driving phenylethanoid glycoside biosynthesis. By contrast, mature cells (cluster 10) show high levels of gene expression relating to carbohydrate metabolism in association with nutrient acquisition. Connecting these insights, we developed a comprehensive C. deserticola database to integrate multi-omics and ecological data (http://60.30.67.246:7006/Home). This builds a robust molecular foundation for exploring pathways to parasitism in plants more broadly.