The complete chloroplast genome of Tamarix ramosissima and comparative analysis of Tamaricaceae species

Tamarix ramosissima is a deciduous shrub that resides in arid and semi-arid regions. Although of ecological and medicinal values, some Tamarix species are considered invasive as they have dominated the riparian zones of dryland in some parts of the world. Here, the complete chloroplast (cp) genome of T. ramosissima was sequenced and analyzed, showing a size of 156 150 bp and a GC content of 36.5 %. The plastome displayed a typical quadripartite structure, consisting of a pair of inverted repeat (IR) regions of 26 554 bp, separated by a large single copy (LSC) region of 84 795 bp, and a small single copy (SSC) region of 18 247 bp. The cp genome encoded 130 genes, including 85 proteincoding genes, 37 tRNA genes, and 8 rRNA genes. A total of 32 repeat sequences and 64 simple sequence repeat (SSR) were identified in the plastome, and an obvious A/T bias was observed in the majority of the SSRs detected. By comparing the T. ramosissima cp genome with those of the other four Tamaricaceae species, a number of divergence hotspots were identified among these plastomes. Together with SSRs and long repeats identified, these divergence hotspots could be developed as potential molecular markers facilitating species discrimination and evolutionary studies. Using plastome sequences, we re-investigated the phylogenetic relationship among 19 species, and T. ramosissima was found to be a sister of Tamarix chinensis. Taken together, our study provides valuable genomic resources to deepen the understanding of plant photosynthetic mechanism and phylogenomics.