- Two different thymidylate kinase gene homologues, including one that has catalytic activity, are encoded in the onion yellows phytoplasma genome. Miyata, S., Oshima, K., Kakizawa, S., Nishigawa, H., Jung, H.Y., Kuboyama, T., Ugaki, M., Namba, S. Microbiology (Reading, Engl.) (2003)