Regulation of metabolomics in Atriplex halimus growth under salt and drought stress

Forty-day-old Atriplex halimus seedlings were treated with either NaCl (50, 300 and 550 mM) for the subsequent 30 days or PEG for the following 3, 6 and 10 days. Shoot fresh and dry weights were significantly increased by 50 mM NaCl; nevertheless, the other concentrations had no effect. However, the growth was reduced by drought only after 10 days. Meanwhile, Na+ was accumulated in treated plants; the magnitude of accumulation was highest with high NaCl concentration or PEG for 10 days. The metabolite profiles showed discrimination particularly up-regulation of the amino acids proline, valine, isoleucine, and methionine. Moreover, the macro analysis revealed that NaCl- and PEG-treated plants shared 10 % of the metabolites in the positive mode, however, 87 % were unique to NaCl and 46 % were unique to PEG whereas in the negative mode, 8 % were in share while 90 or 53 % were restricted to NaCl or PEG, respectively. Additionally, sucrose in particular was significantly increased up to threefold and fivefold by 300 and 550 mM NaCl, respectively and up to 2.5-fold by drought for 10 days, nevertheless, the other sugar fractions remained largely unchanged. Also, proline was significantly increased by only the high NaCl concentrations and the long-term drought, nonetheless, the other treatments led, if any, to decreases. These results conclude that NaCl affects the metabolite profiles more than PEG and these metabolites might contribute to osmotic adjustments to act as osmoprotectants rather than osmolytes. These changes of metabolomics might function in many resistance and stress responses.