Chloroplast genome sequence of triploid Toxicodendron vernicifluum and comparative analyses with other lacquer chloroplast genomes

Abstract

Background: Toxicodendron vernicifluum, belonging to the family Anacardiaceae, is an important commercial arbor species, which can provide us with the raw lacquer, an excellent adhesive and painting material used to make lacquer ware. Compared with diploid, triploid lacquer tree has a higher yield of raw lacquer and stronger resistance to stress. Triploid T. vernicifluum was a newly discovered natural triploid lacquer tree. However, the taxonomy of triploid T. vernicifluum has remained uncertain. Here, we sequenced and analyzed the complete chloroplast (cp) genome of triploid T. vernicifluum and compared with T. vernicifluum cv. Dahongpao, T. vernicifluum cv. Hongpigaobachi, T. vernicifluum and T. succedaneum based on chloroplast genome and SSR markers. Results: The plastome of triploid T. vernicifluum is 158,221 bp in length, including a pair of inverted repeats (IRs) of 26,462 bp, separated by a large single-copy region of 86,951 bp and a small single-copy region of 18,346 bp. In total, 116 unique genes including 82 protein-coding genes, 30 tRNA genes and 4 rRNA genes were identified in the triploid T. vernicifluum. After nucleotide substitutions, small inversions were analyzed in the chloroplast genomes, five hotspot regions were found, which could be useful molecular genetic markers for future population genetics. Phylogenetic analyses showed that triploid T. vernicifluum was a sister to T. vernicifluum cv. Dahongpao and T. vernicifluum cv. Hongpigaobachi.Moreover, phylogenetic clustering based on the SSR markers showed that all the individuals of triploid T. vernicifluum, T. vernicifluum cv. Dahongpao and T. vernicifluum cv. Hongpigaobachi in one group, while the individuals of T. vernicifluum and T. succedaneumin another group. Conclusions: The current genomic datasets provide pivotal genetic resources to determine the phylogenetic relationships, variety identification, breeding and resource exploitation, and future genetic diversity-related studies of T. vernicifluum.