This plasmid is designed for expression of Nucleoplasm-targeted CoralHue® humanized-codon dimeric Keima-570 (NP-hdKeima570) in mammalian cells. CoralHue® hdKeima570, which was originally cloned from the stony coral whose Japanese name is “Komon-Sango.” CoralHue® hdKeima570 absorbs light maximally at 440 nm and emits orange-red light at 570 nm. Thus CoralHue® hdKeima570 exhibits an extremely large Stokes shift (130 nm). Targeting of hdKeima570 to the Nucleoplasm is achieved with the signal peptide fused to the C-terminus of hdKeima570.