STARCH SYNTHESIS, AND TUBER STORAGE PROTEIN GENES ARE DIFFERENTLY EXPRESSED IN SOLANUM-TUBEROSUM AND IN SOLANUM-BREVIDENS

Studying in vitro stem cuttings of Solanum tuberosum induced for tuber ization and those of a non-tuberizing Solanum species, differences bot h in morphology and in gene expression were detected. Stolen formation essentially depended on light while tuberization was triggered by the elevated level of sucrose in the medium. Genes involved in starch syn thesis were induced by sucrose in both species, however, starch granul es were detected only in potato, A new tuber specific cDNA clone, GM7, encoding a putative metallocarboxypeptidase inhibitor and the cDNA of a proline rich cell mall protein with S. brevidens specific expressio n were isolated by differential screening. Sucrose mediated transcript ion of the tuber storage proteins like patatin and proteinase inhibito rs (Kunitz-type, winI, GM7) failed in S. brevidens.