Comprehensive analysis of complete chloroplast genome sequence of Plantago asiatica L. (Plantaginaceae)

Chloroplast genome of Justicia procumbens: genomic features, comparative analysis, and phylogenetic relationships among Justicieae species

Justicia procumbens L. is a traditional medicinal plant that is widely distributed in China. However, little is known about the genetic diversity and evolution of this genus, and no genomic studies have been carried out on J. procumbens previously. In this study, we aimed to assemble and annotate the first complete chloroplast genome (cpDNA) of J. procumbens and compare it with all previously published cpDNAs within the tribe Justicieae. Genome structure and comparative and phylogenetic analyses were performed. The 150,454 bp-long J. procumbens cpDNA has a circular and quadripartite structure consisting of a large single copy, a small single copy, and two inverted repeat regions. It contains 133 genes, of which 88 are protein-coding genes, 37 are tRNA genes, and eight are rRNA genes. Twenty-four simple sequence repeats (SSRs) and 81 repeat sequences were identified. Comparative analyses with other Justicieae species revealed that the non-coding regions of J. procumbens cpDNA showed greater variation than did the coding regions. Moreover, phylogenetic analysis based on 14 cpDNA sequences from Justicieae species showed that J. procumbens and J. flava were most closely related. This study provides valuable genetic information to support further research on the genetic diversity and evolutionary development of the tribe Justicieae.

Comprehensive Analysis of the Complete Chloroplast Genome of Cinnamomum daphnoides (Lauraceae), An Endangered Island Endemic Plant

Cinnamomum daphnoides (Siebold & Zucc 1846) is a rare and endangered island species with a unique Sino-Japanese distribution pattern. However, inormation regarding the species' chloroplast (cp) genome, structural features, and the phylogenetic relationship is still lacking. We utilized high-throughput sequencing technology to assemble and annotate the first cp genome of C. daphnoides (GenBank OR654104), followed by genomic characterization and phylogenetic analysis to fill the gaps in this species' cp genome. Our analysis showed that the cp genome has a quadripartite structure spanning 152,765 bp with a GC content of 39.15%. The genome encodes 126 genes, which include 36 tRNA genes, 8 rRNA genes, and 82 mRNA genes. Specifically, 44 genes are related to photosynthesis, 59 are associated with self-replication, six are other genes, and four have unknown functionality. The Codon usage bias in the genome exhibits a preference for A/U bases. We identified 29 interspaced repeat sequences that belonging to three types of repeat sequences. A total of 217 cpSSR loci were detected with single nucleotide repeats (59.91%) being the most frequent loci, mainly composed of A/T repeats. Our selection pressure analysis revealed that the ycf2 gene experienced strong positive selection (Ka/Ks = 1.81, P > 0.844). Further, we identified three highly variable fragments (psbM, psbT, and ycf1) that can be utilized as specific DNA barcoding markers for species definition and population genetic studies. We conducted boundary analysis, which showed that the structure and gene sequence of the two species were highly conserved. Finally, our phylogenetic analysis supports that C. daphnoides is close to C. cassia in the Cinnamomum genes, indicating that the two species share a common ancestry. Overall, providing genomic information on C. daphnoides will be beneficial for the conservation and utilization of endangered plant genetic resources. It will also serve as a reference for the identification of species and the phylogenetic analysis of Cinnamomum. This information will be useful in future research.