Biochemical and genetic analysis of different patatin isoforms expressed in various organs of potato ( Solanum tuberosum)

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Patatin, a group of glycoproteins in potato ( Solanum tuberosum), is encoded by a multigene family. The protein is found in mass amounts in potato tubers and considered to represent the main storage protein. However, unlike other storage proteins patatin displays enzymatic activity and furthermore, related proteins are found in lower amounts in organs of potato plants which do not serve as storage organs, i.e. stolons, roots and flowers. Evidence is presented showing differences in the enzymatic activities of patatin purified from these organs. The possible implications of these results are discussed. In a genetical approach two single isoforms derived from a class I resp. a class II patatin gene were expressed in transgenic tobacco plants under control of heterologous promoters in order to reduce the complexity of the gene family. The enzymatic activity of these single isoforms was compared to that of patatin of different organs. A class I specific isoform showed exactly the same activity profile as tuber derived patatin. A class II specific isoform showed a pattern different from both tuber and root patatin.