Analysis of codon usage patterns in 48 Aconitum species.

BACKGROUND: The Aconitum genus is a crucial member of the Ranunculaceae family. There are 350 Aconitum species worldwide, with about 170 species found in China. These species are known for their various pharmacological effects and are commonly used to treat joint pain, cold abdominal pain, and other ailments. Codon usage bias (CUB) analysis contributes to evolutionary relationships and phylogeny. Based on protein-coding sequences (PCGs), we selected 48 species of Aconitum for CUB analysis. RESULTS: The results revealed that Aconitum species had less than 50% GC content. Furthermore, the distribution of GC content was irregular and followed a trend of GC1 > GC2 > GC3, indicating a bias towards A/T bases. The relative synonymous codon usage (RSCU) heat map revealed the presence of conservative codons with slight variations within the genus. The effective number of codons (ENC)-Plot and the parity rule 2 (PR2)-bias plot analysis indicate that natural selection is the primary factor influencing the variation in codon usage. As a result, we screened various optimal codons and found that A/T bases were preferred as the last codon. Furthermore, our Maximum Likelihood (ML) analysis based on PCGs among 48 Aconitum species yielded results consistent with those obtained from complete chloroplast (cp.) genome data. This suggests that analyzing mutation in PCGs is an efficient method for demonstrating the phylogeny of species at the genus level. CONCLUSIONS: The CUB analysis of 48 species of Aconitum was mainly influenced by natural selection. This study reveals the CUB pattern of Aconitum and lays the foundation for future genetic modification and phylogenetic analyses.

The chloroplast genomes of two medicinal species (Veronica anagallis-aquatica L. and Veronica undulata Wall.) and its comparative analysis with related Veronica species.

Veronica anagallis-aquatica L. and Veronica undulata Wall. are widely used ethnomedicinal plants in China. The two species have different clinical efficacies, while their extremely similar morphology and unclear interspecific relationship make it difficult to accurately identify them, leading to increased instances of mixed usage. This article reports on the complete chloroplast genomes sequence of these two species and their related Veronica species to conduct a comparative genomics analysis and phylogenetic construction. The results showed that the chloroplast (cp) genomes of Veronica exhibited typical circular quadripartite structures, with total lengths of 149,386 to 152,319 base pairs (bp), and GC content of 37.9 to 38.1%, and the number of genes was between 129-134. The total number of simple sequence repeats (SSRs) in V. anagallis-aquatica and V. undulata is 37 and 36, while V. arvensis had the highest total number of 56, predominantly characterized by A/T single bases. The vast majority of long repeat sequence types are forward repeats and palindromic repeats. Selective Ka/Ks values showed that three genes were under positive selection. Sequence differences often occur in the non-coding regions of the large single-copy region (LSC) and small single-copy region (SSC), with the lowest sequence variation in the inverted repeat regions (IR). Seven highly variable regions (trnT-GGU-psbD, rps8-rpl16, trnQ-UUG, trnN-GUU-ndhF, petL, ycf3, and ycf1) were detected, which may be potential molecular markers for identifying V. anagallis-aquatica and V. undulata. The phylogenetic tree indicates that there is a close genetic relationship between the genera Veronica and Neopicrorhiza, and V. anagallis-aquatica and V. undulata are sister groups. The molecular clock analysis results indicate that the divergence time of Veronica may occur at ∼ 9.09 Ma, and the divergence time of these two species occurs at ∼ 0.48 Ma. It is speculated that climate change may be the cause of Veronica species diversity and promote the radiation of the genus. The chloroplast genome data of nine Veronica specie provides important insights into the characteristics and evolution of the chloroplast genome of this genus, as well as the phylogenetic relationships of the genus Veronica.