Canis familiaris tissues are characterized by different profiles of cytokinins typical of the tRNA degradation pathway.

Cytokinins (CKs) are a group of phytohormones essential to plant growth and development. The presence of these N-modified adenine derivatives has also been documented in other groups of organisms, including bacteria, fungi, and insects. Thus far, however, only a single CK, N-(Δ-isopentenyl) adenine-9-riboside (iPR), has been identified in mammals. In plants, the nucleotide form of isopentenyladenine [iPR (either mono-, di-, or tri-) phosphate (iPRP)] is the first form of CK synthesized, and it is further modified to produce other CK types. To determine if a similar biosynthesis pathway exists in mammals, we tested for the presence of 27 CKs in a wide selection of canine organs using HPLC electrospray ionization-tandem mass spectrometry. Seven forms of CK were detected in the majority of the analyzed samples, including iPR, iPRP, cis-zeatin-9-riboside, cis-zeatin-9-riboside-5' (either mono-, di-, or triphosphate), 2-methylthio-N-isopentenyladenine, 2-methylthio-N-isopentenyladenosine, and 2-methylthio-zeatin. Total CK concentrations ranged from 1.96 pmol/g fresh weight (adrenal glands) to 1.40 × 10 pmol/g fresh weight (thyroid). The results of this study provide evidence that mammalian cells, like plant cells, can synthesize and process a diverse set of CKs including cis- and methylthiol-type CKs.-Seegobin, M., Kisiala, A., Noble, A., Kaplan, D., Brunetti, C., Emery, R. J. N. Canis familiaris tissues are characterized by different profiles of cytokinins typical of tRNA degradation pathway.