Regulation of the compatible osmolyte inositol in gills of tilapia during salinity stress

DIETMAR KÜLTZ, DIEGO FIOL, ROMINA SACCHI, ALISON GARDELL

Barcelona

Congreso; 9th International Congress on the Biology of Fish; 2010

American Fisheries Society

Myo-inositol is a compatible osmolyte utilized by most organisms for maintaining intracellular ion homeostasis during extreme fluctuations of environmental salinity. We have recently identified myo-inositol-phosphate synthase (MIPS) - the key enzyme myo-inositol synthesis - as an immediate early osmotic stress response gene in gills of euryhaline tilapia (Oreochromis mossambicus). The tilapia MIPS gene is structurally highly conserved but lacks a short region that encodes an external loop in other MIPS orthologes. Tilapia MIPS is rapidly transcriptionally induced in response to hyperosmotic stress and shows a biphasic mode of upregulation in tilapia gills. The initial induction peaks between 2 – 6 h and is transient and the second, long-term induction is permament and proportional to the degree of salinity change. In contrast to fish using MIPS for myo-insoitol synthesis during hyperosmotic stress, mammalian cells primarily accumulate inositol via uptake using Sodium-myo-inositol co-transporter (SMIT). Evolutionary implications of these different strategies will be discussed.