Inositol(1,4,5)trisphosphate production in plant cells: an early response to salinity and hyperosmotic stress.

Salinity and hyperosmotic stress are environmental factors that severely affect the growth and development of plants. Adaptation to these stresses is known to be a complex multistep process, but a rise in cytoplasmic Ca(2+) and increased polyphosphoinositide turnover have now been identified as being amongst the early events leading to the development of tolerance. To determine whether a causal link exists between these two events we have investigated the effects of several salts and osmotic agents on levels of inositol(1, 4,5)trisphosphate (Ins(1,4,5)P(3)) in plant cells. Our data show that salts as well as osmotic agents induce a rapid and up to 15-fold increase in cellular Ins(1,4,5)P(3) levels. The increase in Ins(1,4,5)P(3) occurs in a dose-dependent manner and levels remain elevated for at least 10 min. These data indicate that increased Ins(1,4,5)P(3) production is a common response to salt and hyperosmotic stresses in plants and that it may play an important role in the processes leading to stress tolerance.