Insights into the multi-chromosomal mitochondrial genome structure of the Xero- halophytic plant Haloxylon ammodendron (C.A.Mey.) Bunge ex Fenzl

Abstract

Abstract Background Haloxylon ammodendron is an important ecological plant due to its adaptation ability in desert conditions, halophytic environments, and the fixation of sand. It is a promising plant with the ecological value that could help carbon sequestration and a valuable C4 plant model for elucidating the genetic basis of extreme drought tolerance. Although plastid and nuclear genomes were made available, the lack of a mitochondrial genome hampered comprehensive insights into its mitogenome structure organization and phylogenetic implications. Results In the present study, the mitochondrial genome of H. ammodendron was assembled and annotated, resulting in a multi-chromosomal configuration with two circular chromosomes. The mitogenome was 210,149 bp in length and contained 31 protein-coding genes, 18 tRNA, and three rRNA. A total of 66 simple sequence repeats (SSRs) were identified. Besides, 27 tandem repeats, 312 forward repeats, and 303 palindromic repeats were found. A set of 17 sequence fragments were found homologous between the mitochondrial and chloroplast genomes, spanning 5,233 bp, accounting for 2.49% of the total mitogenome size. In total, 337 RNA editing sites were predicted, all C-to-U conversion types. Phylogenetic inference confidently placed H. ammodendron in the Amaranthacea family and its close relative, Suaeda glacum. Conclusions H. ammodendron mitogenome showed a multi-chromosome structure with two fully circularized molecules. The present mitogenome represents a valuable resource for understanding the basis of mitogenome structure variation within Caryophyllales and evolution in land plants, their identification, and classification.