金缕梅科植物叶绿体基因组序列比较分析OA

To determine the fundamental features of the chloroplast genome sequences and the evolutionary relationships of Hamamelidaceous plants,the complete chloroplast genome sequences of 20 species of 17 genera in the Hamamelidaceae family were analyzed by the comparative genome approach,mainly focusing on the structural features of the genomes,sequence differences,and evolutionary relationships.The results showed that the chloroplast genomes of the 20 species of Hamamelidaceae were typical tetrameric struc-tures,all of which were composed of LSC,SSC,IRA and IRB,with the full length of 158 076-160 744 bp,the GC content of 37.8%-37.9%,and the AT contents of all of them were 62.1%-62.2%,with obvious AT bias.The greatest polymorphism of petA-psbJ was found in the LSC region(0.082 88),whereas all of the sequences in the IRs region exhibited significant conservation with Pi values below 0.055.In the cyclic chloroplast genome,the four border regions are relatively conserved,but there are still some differences among species in the non-coding regions.In the chloroplast genomes of 20 plant species,a total of 1 162 SSRs(simple sequence repeats)were detected,among which mononucleotide repeats were the most abun-dant,with 882 occurrences,accounting for 75.9%of the total SSRs.In the phylogenetic tree of chloroplast whole genome sequences Distylium and the Shaniodendron clustered into a single unit to be the first to di-verge with a recent common ancestor.This study demonstrated stable adaptive evolution in the Hamameli-daceae family and established the phylogenetic relationships among its species.