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The complete chloroplast genome of Zoysia macrostachya Franch. & Sav. isolated in Korea is 135,902 bp long (GC ratio is 38.4%) and has four subregions; 81,546 bp of large single-copy (36.3%) and 12,586 bp of small single-copy (32.7%) regions are separated by 20,885 bp of inverted repeat (44.1%) regions, including 130 genes (83 protein-coding genes, eight rRNAs, and 39 tRNAs). Thirty-nine single nucleotide polymorphisms and 11 insertions and deletion (INDEL) regions were identified from two Z. macrostachya chloroplast genomes, the smallest among other Zoysia species. Phylogenetic trees show that two Z. macrostachya chloroplast genomes are clustered into a single clade. However, we found some incongruency with regard to the phylogenetic position of the Z. macrostachya clade. Our chloroplast genome provides insights into intraspecific variations and species delimitation issues pertaining to the Zoysia species.

Zoysia macrostachya Franch. et Sav. is a halophyte with very strong tolerance to salinity, which can serve as an alternative turfgrass for landscaping in saline-alkali land and provide the salt-tolerance genes for turfgrass breeding. To further illustrate the salt-tolerance mechanisms in this species at molecular level, the roots transcriptome of Z. macrostachya was investigated under salt stress using the Illumina sequencing platform. Altogether 47,325 unigenes were assembled, among which, 32,542 (68.76%) were annotated, and 87.61% clean reads were mapped to the unigenes. Specifically, 14,558 unigenes were shown to be the differentially expressed genes (DEGs) following exposure to 710 mM NaCl stress compared with control, including 7972 up-regulated and 6586 down-regulated DEGs. Among these DEGs, 24 were associated with the reactive oxygen species (ROS) scavenging system, 61 were found to be related to K+ and Na+ transportation, and 16 were related to the metabolism of osmotic adjustment substances. Additionally, 2327 DEGs that encoded the transcription factors (TFs) were also identified. The expression profiles for 10 DEGs examined through quantitative real-time PCR conformed to the individual alterations of transcript abundance verified through RNA-Seq. Taken together, results of transcriptome analysis in this study provided useful insights for salt-tolerance molecular mechanisms of Z. macrostachya. Furthermore, these DEGs under salt stress provided important clues for future salt-tolerance genes cloning of Z. macrostachya. © 2021 Friends Science Publishers

As one of the most severe environmental stresses, salt stress can cause a series of changes in plants. In salt tolerant plant Zoysia macrostachya, germination, physiology, and genetic variation under salinity have been studied previously, and the morphology and distribution of salt glands have been clarified. However, no study has investigated the transcriptome of such species under salt stress. In the present study, we compared transcriptome of Z. macrostachya under normal conditions and salt stress (300 mmol/L NaCl, 24 h) aimed to identify transcriptome responses and molecular mechanisms under salt stress in Z. macrostachya. A total of 8703 differently expressed genes (DEGs) were identified, including 4903 up-regulated and 3800 down-regulated ones. Moreover, a series of molecular processes were identified by Gene Ontology (GO) analysis, and these processes were suggested to be closely related to salt tolerance in Z. macrostachya. The identified DEGs concentrated on regulating plant growth via plant hormone signal transduction, maintaining ion homeostasis via salt secretion and osmoregulatory substance accumulation and preventing oxidative damage via increasing the activity of ROS (reactive oxygen species) scavenging system. These changes may be the most important responses of Z. macrostachya under salt stress. Some key genes related to salt stress were identified meanwhile. Collectively, our findings provided valuable insights into the molecular mechanisms and genetic underpinnings of salt tolerance in Z. macrostachya.