Complete Chloroplast Genome Sequence Structure and Phylogenetic Analysis of Kohlrabi (Brassica oleracea var. gongylodes L.)

Abstract

Kohlrabi is an important swollen-stem cabbage variety belonging to the Brassicaceae family. However, few complete chloroplast genome sequences of this genus have been reported. Here, a complete chloroplast genome with a quadripartite cycle of 153,364 bp was obtained. A total of 132 genes were identified, including 87 protein-coding genes, 37 transfer RNA genes and eight ribosomal RNA genes. The base composition analysis showed that the overall GC content was 36.36% of the complete chloroplast genome sequence. Relative synonymous codon usage frequency (RSCU) analysis showed that most codons with values greater than 1 ended with A or U, while most codons with values less than 1 ended with C or G. Thirty-five scattered repeats were identified and most of them were distributed in the large single-copy (LSC) region. A total of 290 simple sequence repeats (SSRs) were found and 188 of them were distributed in the LSC region. Phylogenetic relationship analysis showed that five Brassica oleracea subspecies were clustered into one group and the kohlrabi chloroplast genome was closely related to that of B. oleracea var. botrytis. Our results provide a basis for understanding chloroplast-dependent metabolic studies and provide new insight for understanding the polyploidization of Brassicaceae species.