No abstract

199LBetaines and free amino acids in salt stressed vitroplants and winter resting buds of Populus trichocarpa x de/ (oWra, Organic solutes, in particular glycine betaine and proline, have been detected as osmoprotective compounds in many microorganisms and herbaceous species. However, for woody plants, very little information is available on mechanisms of adaptation to salt stress. In the present study, effects of NaCI treatment on betaine and free amino acid contents in a clone of Populus trichocarpa x deltoides micropropagated vitroplants were analyzed using HPLC and silicate plate chromatography. The application during 12 days of 50 to 200' mM NaCl to vitroplants cultured on Murashige and Skoog medium (Murashige and Skoog 1962, Physioi, Plant. 15: 473-497) led to a progressive decrease of growth, leaf senescence, abscission, and apical necrosis, Populus trichocarpa x dehoides was characterized by the absence of glycine betaine and/oT proline accumulation. However, trigonelline was found to increase in vitroplants subjected lo 100 mM NaCI. Trigonelline was also' present in dormant buds harvested in natural conditions and missing in active buds. In vitroplants, the content of some amino acids was strongly modified by salt stress, A progressive accumulation of alanine and 7-amino butyrale was particularly significant in roots, whereas the relative concentration of glutamine was strongly enhanced in leaves. Leaf content of glutamate and ornithine attained maximum in the presence of 100 and 150 mM NaCl concentrations, and then deereased. Arginine and serine pools were not significantly modified by salt treatment. The variations in vitroplants were of small amplitude connpared to those obser\'ed in mature poplars where winter rest was associated with a very high arginine level and with a disappearance of nearly all other free amino acids. The results are discussed in relation to previous data obtained with herbaceous species and in relation to some metabolic pathways in poplars where trigoneiline could be considered as a sensitive stress indicator.

Background: G protein-coupled receptor functions are regulated by phosphorylation. Results: Mass spectrometry was used to map the phosphorylation sites of the NPFF 2 neuropeptide FF receptor, and site-directed mutagenesis permitted the identification of their role in receptor regulation. Conclusion: Sites involved in desensitization and internalization do not fully overlap. Significance: This is the first mapping of NPFF 2 receptor phosphorylation.