Abstract

The relatively short life cycle and small size of Arabidopsis thaliana makes this plant a suitable model organism for biochemical and molecular biology studies. In our laboratory, we undertook the characterization of the 18 sulfotransferase-coding genes of this small flowering plant. This thesis describes the results of the biochemical and functional characterization of AtST10, one of these genes.

Probably the most interesting features of AtST10 are its expression (restricted to the siliques, the plant’s fruit) and the possibility of a miRNA regulating its expression in an indirect manner. We also demonstrate that the overexpression of AtSt10 leads to a reduction in seed production to altered size compared with wild type plants suggesting that the AtST10 substrate or product plays a role in seed development. Alternatively, AtST10 might participate in the metabolism of another jasmonate which is involved in seed development. Using a combination of different purification methods and mass spectrometry we identified the putative reaction product of the AtST10-catalyzed reaction. This molecule has a m/z of 307 Da in positive mode [M+H] and generates fragments similar to the ones observed with 12- hydroxyjasmonate. Based on these results, we propose that the product of the reaction is the reduced form of 12-hydroxyjasmonate sulfate. This is the first report of the natural occurrence of this molecule in plants. Further experiments will be required to define the role of this metabolite or of its sulfonated product in seed development.