Chen C, Xia X, Peng J, Wang D. Comparative Analyses of Six Complete Chloroplast Genomes from the Genus Cupressus and Juniperus (Cupressaceae).
Gene 2022;
837:146696. [PMID:
35738448 DOI:
10.1016/j.gene.2022.146696]
[Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 06/05/2022] [Accepted: 06/17/2022] [Indexed: 11/26/2022]
Abstract
Cupressaceae is a conifer family distributed around the world. Cupressus and Juniperus are the main genera of the Cupressaceae family and have important medicinal value. This leads to confusion between Cupressus and Juniperus due to similar morphologies. Here, the complete cp genomes of two Cupressus (C. duclouxiana and C. funebri) and four Juniperus (J. chinensis, J. gaussenii J. pingii and J. procumbens) were sequenced. The results revealed that the length of the cp genomes ranged from 126,996 bp to 129,959 bp, with 119 genes comprising 82 protein-coding genes, 33 transfer RNAs and 4 ribosomal RNAs. All chloroplast genomes of Cupressus and Juniperus lost whole IR regions, which is consistent with gymnosperm cp genome studies. In addition, the number of SSRs per species ranged from 54 to 73 and was dominated by mononucleotide repeats. In the six cp genomes of Cupressus and Juniperus, five highly divergent regions, including accD, accD-rpl2, ycf1, ycf2 and rrn23-rrn4.5, can be used as DNA barcodes of interspecific relationships and potential genetic markers. We compared the gene selection pressures (C. chengiana as reference species), and 6 genes underwent positive selection, the majority of which were related to photosynthesis. Phylogenetic results showed that the monophyly of Cupressus and Juniperus supported most bootstrap support. Cupressus funebris and J. chinensis were resolved to be early diverging species within Cupressus and Juniperus, and the two genera were sister groups to each other. This research revealed a new understanding of the structural pluralism and phylogenetic relationships of Cupressaceae cp genomes. These results will facilitate comprehension of the complexity and diversity of conifer cp genomes. SIGNIFICANCE:: Phylogenetic relationships among Cupressus, Juniperus, and their closest relatives are controversial, and generic delimitations have been in flux for the past decade. To address relationships and attempt to produce a more robust classification, we sequenced 6 new plastid genomes (plastomes) from the two variously described genera in this complex (Cupressus and Juniperus) and compared them with additional plastomes from diverse members of Cupressaceae. Our study corroborated the accD of Cupressophytes have a tendency to expand in size and strongly supported a sister relationship between Cupressus and Juniperus. The disparity in these results could be traced to the facts that the chloroplast genome is uniparentally inherited, also the usage of the whole chloroplast genome for this research is of a better advantage compared to usage of selected genes or portion of the plastome. The complete CP genomic data will provide useful information for studying genetic diversity and species identification, which is important for the overarching goal of biodiversity conservation.
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