Sesame (Sesamum indicum L.) is an important oilseed crop that produces abundant seed oil and has a pleasant flavor and high nutritional value. To date, several Illumina-based genome assemblies corresponding to different sesame genotypes have been published and widely used in genetic and genomic studies of sesame. However, these assemblies consistently showed low continuity with numerous gaps. Here, we reported a high-quality, reference-level sesame genome assembly by integrating PacBio high-fidelity sequencing and Hi-C technology. Our updated sesame assembly was 309.35 Mb in size with a high chromosome anchoring rate (97.54%) and contig N50 size (13.48 Mb), which were better than previously published genomes. We identified 163.38 Mb repetitive elements and 24,345 high-confidence protein-coding genes in the updated sesame assembly. Comparative genomic analysis showed that sesame shared an ancient whole-genome duplication event with two Lamiales species. A total of 2,782 genes were tandemly duplicated. We also identified several genes that were likely involved in fatty acid and triacylglycerol biosynthesis. Our improved sesame assembly and annotation will facilitate future genetic studies and genomics-assisted breeding of sesame.

Dichrocephala benthamii C. B. Clarke has long been used as traditional Chinese medicine. However, the chloroplast (cp) genome of D. benthamii is poorly understood so far. In this study, we have sequenced and analyzed the cp genome of D. benthamii. The results show that the cp genome is 152,350 bp in length, with a pair of inverted repeat regions (IRa and IRb, each 24,982 bp), a large single-copy (LSC) region comprising 84,136 bp, and a small single-copy (SSC) region comprising 18,250 bp. The GC content of the cp genome was 37.3%. A total of 134 genes were identified, including 87 protein-coding genes (CDS), 38 tRNA genes, 8 rRNA genes, and 1 pseudogene (ycf1). The plastome includes 87 simple repeats and 48 long repeats. The phylogenetic analysis reveals D. benthamii is the basal group of Astereae. Therefore, we confirm that the taxa of Astereae emerges from southern Africa and dispersed to other big continents. The results of this study are a significant contribution to the field of genetics and species identification related to D. benthamii.

The genus of Parasenecio (Senecioneae) comprises about 70 species of high medicinal value. In this study, the plastomes of Parasenecio palmatisectus and P. latipes were newly sequenced using high-throughput sequencing technology and compared with those of eight other species in Senecioneae. The complete chloroplast (cp) genomes were 151,185 bp in P. latipes with 37.5% GC and 151,263 bp in P. palmatisectus with 37.5% GC. We predicted 133 genes, including 37 tRNA genes, 86 protein-coding genes, 8 rRNA genes, and 2 pseudogenes (ycf1 and rps19). A comparative genomic analysis showed that the complete cp genome sequences of Parasenecio species and their related species were relatively conserved. A total of 49 to 61 simple sequence repeats (SSRs) and 34 to 46 interspersed repeat sequences were identified in the 10 Senecioneae species of plastomes. Within the tribe Senecioneae, single-copy regions were more variable than inverted repeats regions, and the intergenic regions were more variable than the coding regions. Two genic regions (ycf1 and ccsA) and four intergenic regions (trnC-GCA-petN, ycf1-trnN-GUU, psaI-ycf4, and rpl32-trnL-UAG) were identified as highly valuable plastid markers. A phylogenetic analysis under maximum likelihood revealed that the two Parasenecio species are sister to the genera of Ligularia and Sinosenecio in the tribe Senecioneae. This study also contributes to the super-barcode, phylogenetic, and evolutionary studies of Parasenecio plants.