Affiliation:
1. Shanghai Chenshan Botanical Garden
2. Zhejiang A&F University
Abstract
Abstract
Background: Cycle-cup oaks (Quercus section Cyclobalanopsis) are one of the principal components of forests in the tropical and subtropical climates of East and Southeast Asia. They have experienced relatively recent increases in the diversification rate, driven by changing climates and the Himalayan orogeny. However, the course, tempo, and mode of genome evolution in cycle-cup oaks remain largely unknown; in particular, how plant plastome genes and genomes evolve during rapid speciation. To address this question, we analyzed the complete plastomes of 50 species of Quercus section Cyclobalanopsis, 36 newly sequenced and 14 published species.
Results: Based on a series of analyses, including genome structure, genome annotation, GC content, repeat sequences, SSR components, codon usage bias, and comparative genomics, we found that Quercus section Cyclobalanopsishad a conserved plastome structure. Highly divergent regions, such as the ndhFand ycf1 gene regions and the petN—psbM and rpoB—trnC-GCA gene spacer regions, provided potential molecular markers for subsequent analysis. The maximum likelihood phylogenetic tree based on complete chloroplast genomes, coding DNA sequences, and highly divergent regions produced a poorly resolved genetic relationship of the plastid lineages of section Cyclobalanopsis. We identified nine protein-coding genes containing sites for positive selection: ndhA, ndhD, ndhF, ndhH, rbcL, rpl32, accD, ycf1, and ycf2.
Conclusions: We compared and analyzed the chloroplast genomes of 50 species of Quercus section Cyclobalanopsis to explore their diversity structure, phylogenetic relationships, and ecological adaptative evolution. These chloroplast genome data provide valuable information for deep insights into phylogenetic relationships and intraspecific diversity in Quercus.
Publisher
Research Square Platform LLC
Reference111 articles.
1. The oaks of western Eurasia: Traditional classifications and evidence from two nuclear markers;Denk T;Taxon,2010
2. Denk T, Grimm GW, Manos PS, Deng M, Hipp AL et al. An updated infrageneric classification of the Oaks: review of previous taxonomic schemes and synthesis of evolutionary patterns. In: Gil-Pelegrín E, editors. Oaks physiological ecology. Exploring the Functional Diversity of Genus Quercus L. 2017. p. 13–38.
3. Huang CJ, Zhang YT, Hu YC, Jen HW. Fagaceae. In: Chun WY, Huang CJ, editors. Flora of China. 1999. p. 314–400.
4. Camus A. Les Chênes. Monographie du genre Quercus. Tome I. Genre Quercus, sous-genre Cyclobalanopsis, sous-genre Euquercus (sections Cerris et Mesobalanus). Texte; 1936–1938.
5. Phytogeography of Quercus subg. Cyclobalanopsis. (In Chinese;Luo Y;Chin Acta Bot Yunnaica,2001