The Chloroplast Phylogenomics And Systematics Of Zoysia (Poaceae)

The genus Zoysia Willd. (Chloridoideae) is widely distributed from the temperate regions of Northeast Asia-including China, Japan, and Korea-to the tropical regions of Southeast Asia. Among these, four species-Zoysia japonica Steud., Zoysia sinica Hance, Zoysia tenuifolia Thiele, and Zoysia macrostachya Franch. & Sav.-are naturally distributed in the Korean Peninsula. In this study, we report the complete plastome sequences of these Korean Zoysia species (NCBI acc. nos. MF953592, MF967579 similar to MF967581). The length of Zoysia plastomes ranges from 135,854 to 135,904 bp, and the plastomes have a typical quadripartite structure, which consists of a pair of inverted repeat regions (20,962 similar to 20,966 bp) separated by a large (81,348 similar to 81,392 bp) and a small (12,582 similar to 12,586 bp) single-copy region. In terms of gene order and structure, Zoysia plastomes are similar to the typical plastomes of Poaceae. The plastomes encode 110 genes, of which 76 are protein-coding genes, 30 are tRNA genes, and four are rRNA genes. Fourteen genes contain single introns and one gene has two introns. Three evolutionary hotspot spacer regions-atpB similar to rbcL, rps16 similar to rps3, and rpl32 similar to trnL-UAG-were recognized among six analyzed Zoysia species. The high divergences in the atpB similar to rbcL spacer and rpl16 similar to rpl3 region are primarily due to the differences in base substitutions and indels. In contrast, the high divergence between rpl32 similar to trnL-UAG spacers is due to a small inversion with a pair of 22 bp stem and an 11 bp loop. Simple sequence repeats (SSRs) were identified in 59 different locations in Z. japonica, 63 in Z. sinica, 62 in Z. macrostachya, and 63 in Z. tenuifolia plastomes. Phylogenetic analysis showed that the Zoysia (Zoysiinae) forms a monophyletic group, which is sister to Sporobolus (Sporobolinae), with 100% bootstrap support. Within the Zoysia clade, the relationship of (Z. sinica, Z japonica), (Z. tenuifolia, Z. matrella), (Z. macrostachya, Z. macrantha) was suggested.