Department of Biological and Environmental Sciences, and Institute of Biotechnology, P.O.Box 56 (Viikinkaari 5), 00014 University of Helsinki, Finland. liisa.holm@helsinki.fi|Department of Biological and Environmental Sciences, and Institute of Biotechnology, P.O.Box 56 (Viikinkaari 5), 00014 University of Helsinki, Finland. liisa.holm@helsinki.fi|Department of Biological and Environmental Sciences, and Institute of Biotechnology, P.O.Box 56 (Viikinkaari 5), 00014 University of Helsinki, Finland. liisa.holm@helsinki.fi|Department of Biological and Environmental Sciences, and Institute of Biotechnology, P.O.Box 56 (Viikinkaari 5), 00014 University of Helsinki, Finland. liisa.holm@helsinki.fi