Glycine Betaine Synthesis As Affected By High Light and salinity

Keywords: Glycine betaine, compatible solutes, salt stress, light intensity, durum wheat. Glycine betaine (GB) not only acts as an osmoregulator, but interacts with both hydrophilic and hydrophobic domains of macromolecules stabilizing their structures and activities and maintaining the integrity of membranes against the damaging effects of abiotic stresses. In many halophytes, GB and/or proline concentrations in leaves contribute to the osmotic pressure in the cell as a whole. In glycophytes their concentrations are much lower but, if partitioned exclusively to the cytoplasm, they could generate a significant osmotic pressure and function to balance vacuolar osmotic potential. In this study, we determined the effects of both salinity and high light on durum wheat seedlings, with a special emphasis on the potential role of GB in their protection. Very unexpectedly it appeared that high light treatments inhibit the synthesis of GB, even in the presence of salt stress. In order to understand the mechanisms underlying such result, we investigated the effects of different light intensities on the transcripts encoding enzymes involved in its synthesis. Moreover, additional solutes susceptible to compensate the decrease in GB were followed over this range of light treatments.