The chromosome-scale genome of black wolfberry (Lycium ruthenicum) provides useful genomic resources for identifying genes related to anthocyanin biosynthesis and disease resistance.

Abstract

The black wolfberry (L ycium ruthenicum; 2n = 2x = 24) is an important medicinal plant with ecological and economic value. Its fruits have numerous beneficial pharmacological activities, especially those of anthocyanins, polysaccharides, and alkaloids, and have high nutritional value. However, the lack of available genomic resources for this species has hindered research on its medicinal and evolutionary mechanisms. In this study, we developed the telomere-to-telomere (T2T) nearly gapless genome of L. ruthenicum (2.26 Gb) by integrating PacBio HiFi, Nanopore Ultra-Long, and Hi-C technologies. The assembled genome comprised 12 chromosomes with 37,149 protein-coding genes functionally annotated. Approximately 80% of the repetitive sequences were identified, of which long terminal repeats (LTRs) were the most abundant, accounting for 73.01%. The abundance of LTRs might be the main reason for the larger genome of this species compared to that of other Lycium species. The species-specific genes of L. ruthenicum were related to defense mechanisms, salt tolerance, drought resistance, and oxidative stress, further demonstrating their superior adaptability to arid environments. Based on the assembled genome and fruit transcriptome data, we further constructed an anthocyanin biosynthesis pathway and identified 19 candidate structural genes and seven transcription factors that regulate anthocyanin biosynthesis in the fruit developmental stage of L. ruthenicum, most of which were highly expressed at a later stage in fruit development. Furthermore, 154 potential disease resistance-related nucleotide-binding genes have been identified in the L. ruthenicum genome. The whole-genome and proximal, dispersed, and tandem duplication genes in the L. ruthenicum genome enriched the number of genes involved in anthocyanin synthesis and resistance-related pathways. These results provide an important genetic basis for understanding genome evolution and biosynthesis of pharmacologically active components in the Lycium genus.