The effects of Arabidopsis thaliana Sulfotransferase 2a (AtST2a) over-expression on tuber formation

This thesis describes the study of the effects of Arabidopsis thaliana Sulfotransferase 2a ( AtST2a ) over-expression in potato plants ( Solanum chacoense ). AtST2a encodes a sulfotransferase, that functions to reduce the endogenous levels of a hydroxylated product of jasmonic acid, 12-hydroxyjasmonate (12-OHJA) also known as tuberonic acid. Through phenotypic analysis of transgenic potato lines, AtST2a over-expression was shown to delay tuberization. In addition, tubers in the transgenic lines were smaller and more numerous than in the wild type control lines. Furthermore, regulation studies showed that 12-OHJA induces tuber-specific genes in planta , where, tuber induction previously was only demonstrated in vitro . Tuberonic acid sulfate, the product of the AtST2a sulfonation reaction was detected and quantified in potato leaf segments. This indicates the presence of a potato homologue of AtST2a . Six potential potato candidates were identified, of which two showed the greatest potential (TC77024 & TC87873), based on time course treatment assays. However, substrate specificity experiments showed that TC77024and TC87873 are not hydroxy-jasmonate sulfotransferases