The tow classes of genes for the major potato tuber protein, patatin, are differentially expressed in tubers and roots

Abstract

The major potato tuber protein, patatin, is a family of 40kd glycoproteins that constitutes forty per cent of the soluble protein in tubers but is generally undetectable in other tissues. Fused rocket immunoelectro-phoresis was used to detect in roots patatin that is immunologically different from tuber patatin. Western blots of SDS-polyacrylamide gels show root patatin to have a different molecular weight distribution than tuber patatin isoforms, but immunoprecipitation of in vitro translation products shows the patatin precursors to be of similar molecular weight in both tissues. This suggests that post-translational processing may differ in tubers and roots. Northern blots show that tuber and root patatin mRNAs are of similar size, but tuber transcripts are about 100-fold more abundant. 5' S1 nuclease and primer extension mapping suggests the class of patatin transcripts expressed in roots (class II transcripts) to be a subset of patatin transcripts expressed in tubers (classes I and II). Class II patatin mRNAs differ from class I transcripts by the presence of a 22 nucleotide insertion just upstream of the initiation codon. These data demonstrate that expression of the patatin multigene family is differentially regulated in tubers and roots.

Structural Diversity and Differential Transcription of the Patatin Multicopy Gene Family During Potato Tuber Development

“…b Class I and class II patatins are defined by the absence or presence of a 22-bp insertion in the 59-UTR (Pikaard et al 1987).…”

“…Pikaard et al (1987) found that two classes of patatin genes, distinguished by the presence or absence of 22 nucleotides in the 59-untranslated region (UTR), are differentially expressed Sequence data from this article have been deposited with the EMBL/ GenBank data libraries under the following accession nos. : BAC 14K07, accession no.…”

Gene expression during tuber development in potato plants

“…Based on sequence comparison of the 5'-untranslated regions of the clones, the genes can be separated into two types, which differ by the presence (class II) or absence (class I) of a 22 nucleotide insertion just upstream of the initiation codon. Class I transcripts are tuber specific, wherease class II genes are expressed in both tubers and roots, albeit at a much lower level than class I ones [26].…”

“…In addition, patatin is also expressed in roots, albeit at a IO@fold lower level [26]. Although tuberization is always accompanied by patatin synthesis, there are several instances where its expression is observed in non-tuberizing tissues.…”

Identification of mutants in metabolically regulated gene expression

“…Patatin, as the major storage protein of potato tubers, is encoded by a gene family that can be subdivided into two classes according to structural features and expression profiles (Pikaard et al, 1987). Using a transgenic approach, it could be shown that class I genes were responsible for the high levels of patatin in developing tubers and were inducible in leaves by sucrose, whereas class II gene expression was constitutive and restricted to certain cell types of tubers and roots (K6ster-T6pfer et al, 1989;RochaSosa et al, 1989).…”