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Evolution of Rosaceae chloroplast genomes highlights unique Cerasus diversification and independent origins of fruit cherry

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Sep 10, 2020 version files 149.06 MB

Abstract

Rosaceae plants comprise numerous fruit crops with huge economic values. The lack of genomic characteristics has largely blocked our understanding about the Rosaceae gene and plastome evolution. Here, we analyzed 121 Rosaceae chloroplast (cp) genomes of 51 taxa from 19 genera, predominantly including the Cerasus plants and their relatives. To our knowledge, we generated the first comprehensive map of genomic variation across Rosaceae plastomes. Protein-coding genes of Rosaceae plastomes were characterized with high proportion (over 50%) of synonymous variants and InDels with multiple triplets. Four photosynthesis-related genes were under Darwin selection, which are unique in woody fruit trees of Rosaceae. We detected considerable variations in genome size among Rosaceae plastomes and observed trivial and obvious structural variation in the examined cp genomes of tribes Pyrodae and Amygdaleae. Phylogenomic analyses and molecular dating highlighted the independent evolution of true cherry, dwarf cherry and relatives. Our findings strongly support to taxonomically treat the monophyletic true cherry group as a separate genus excluding dwarf cherry. High levels of genomic differentiation and distinct phylogenetic relationships implied independent origins and domestication between fruit cherries, particularly between cultivated Cerasus psuedocerasus and Cerasus avium. We further proposed an evolutionary model to elucidate multiple genomic introgression events among true cherries occurring since ~15 Mya. Well-resolved maternal phylogeny suggested that the cultivated C. pseudocerasus might be originated from Longmenshan Fault zone, the eastern edge of Himalaya-Hengduan Mountains, where they have subjected to frequent genomic introgression between its presumed wild ancestors and other close relatives. In conclusion, comparative analyses of plastomes and chloroplast genes detected diverse evolutionary behaviors and divergent adaptive selection in Rosaceae. We provide robust evidences for the independent origins and domestication of fruit cherries.