EXPRESSION OF THE TRIOSE PHOSPHATE TRANSLOCATOR GENE FROM POTATO IS LIGHT-DEPENDENT AND RESTRICTED TO GREEN TISSUES

The export of primary photosynthesis products from chloroplasts into t he cytoplasm is mediated by the triose phosphate translocator. The tra nsporter is an integral membrane protein localized at the inner envelo pe of chloroplasts. In order to study the expression of the major chlo roplast envelope protein gene E29, which is assumed to function as the translocator, we have isolated corresponding cDNA clones from potato. A full-length clone was sequenced and shown to be highly homologous t o the E29 gene from spinach. Expression on the RNA level is restricted to green tissues, is light dependent and cannot be induced by sucrose in darkness. The presence of a single-copy gene argues for the existe nce of different translocator systems responsible for import and expor t of carbohydrates in chloroplasts and amyloplasts.