iBlueberry is a monomeric infra-red fluorescent protein with an excitation peak of 644nm and an emission peak of 667nm in vitro. It is an artificial derivative of a bacteriophytochrome gene, 'BrBphP', from a Bradyrhizobium species. iBlueberry was obtained by introducing the single mutation I251C into mIFP, which results in its excitation and emission spectra being blue-shifted by approximately 40 nm compared to mIFP. In order to fluoresce, iBlueberry requires a biliverdin cofactor to act as the chromophore. This can be supplied in a transgenic animal by including a transgenic construct that encodes a heme oxygenase (HO) (PMID:26549191).