菜心叶绿体基因组特征及系统发育分析OA

[Objective]This study aims to assemble,annotate,and analyze the chloroplast genome of flowering Chinese cabbage(Brassica rapa var.parachinensis),and to elucidate its phylogenetic relationships with other Brassicaceae crops.[Method]The complete chloroplast genome of flowering Chinese cabbage was sequenced using the Illumina NovaSeq 6000 platform.Bioinformatics approaches were employed to analyze its genome structure,repetitive sequences,nucleotide diversity,codon usage bias,and phylogenetic relationships by constructing phylogenetic trees with chloroplast genome sequences of other 25 Brassicaceae species.[Result]The chloroplast genome of flowering Chinese cabbage is 153 482 bp in length with a GC content of 36.36%,e xhibiting a typical quadripartite structure.In total,132 functional genes had been identified and annotated,comprising 86 protein-coding genes,37 tRNA genes,8 rRNA genes,and 1 pseudogene.Codon usage bias analysis revealed that leucine(Leu)is the most frequently used amino acid,with 31 codons showing a relative synonymous codon usage(RSCU)value greater than 1,predominantly ending with A or U.Repetitive sequence analysis detected 37 dispersed repeats and 315 simple sequence repeats(SSRs),with mononucleotide repeats predominating(72.70%of total SSRs).The nucleotide diversity of small single copy region(SSC)is the highest,while that of inverted repeat region(IR)is the lowest.Phylogenetic analysis revealed that flowering Chinese cabbage exhibits the closest genetic relationship with leafy Chinese cabbage varieties.[Conclusion]The chloroplast genome of flowering Chinese cabbage exhibits a conserved quadripartite structure and demonstrates close phylogenetic relationships with B.rapa var.chinensis,B.rapa var.purpuraria,and B.rapa subsp.pekinensis.[Ch,5 fig.3 tab.39 ref.]