| Summary: | Phytoene synthase (PSY) is a key limiting enzyme in the carotenoid biosynthesis pathway for regulating phytoene synthesis. In this study, <i>ZjPSY</i> was isolated and identified from <i>Zoysia japonica</i>, an important lawn grass species. <i>ZjPSY</i> cDNA was 1230 bp in length, corresponding to 409 amino acids. <i>ZjPSY</i> showed higher expression in young leaves and was downregulated after GA<sub>3</sub>, ABA, SA, and MeJA treatments, exhibiting a sensitivity to plant hormones. Regulatory elements of light and plant hormone were found in the upstream of <i>ZjPSY</i> CDS. Expression of <i>ZjPSY</i> in <i>Arabidopsis thaliana</i> protein led to carotenoid accumulation and altered expression of genes involved in the carotenoid pathway. Under no-treatment condition, salt treatment, and drought treatment, transgenic plants exhibited yellowing, dwarfing phenotypes. The carotenoid content of transgenic plants was significantly higher than that of wild-type under salt stress and no-treatment condition. Yeast two-hybrid screening identified a novel interacting partner <i>ZjJ2</i> (<i>DNAJ homologue 2</i>), which encodes heat-shock protein 40 (HSP40). Taken together, this study suggested that ZjPSY may affect plant height and play an important role in carotenoid synthesis. These results broadened the understanding of carotenoid synthesis pathways and laid a foundation for the exploration and utilization of the <i>PSY</i> gene.
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