Class I patatin genes from potato (Solanum tuberosum L.) cultivars: molecular cloning, sequence comparison, prediction of diverse cis-regulatory motifs, and assessment of the promoter activities under field and in vitro conditions

Abstract

Patatin, the most abundant glycoprotein (∼40 kDa) in potato (Solanum tuberosum L.) tuber is encoded by a large multigene family comprising of two classes. Class I patatin gene promoters are attractive molecular tools for studying multiple facets of transcriptional regulation. Only a few members of this class are relatively well understood at the molecular level. Here, we report the isolation of two new partial class I patatin genes with corresponding 5′-flanking regions, designated as StPN02 and StPK01, from two commercially important Indian potato cultivars, ‘Kufri Jyoti’ and ‘Kufri Chipsona-1’, respectively. Their 5′-flanking regions were found to vary significantly because of insertions/deletions in addition to point mutations. A major 487-bp insertion in the 5′-flanking region of StPN02 was a distinctive from other family members. Many of the diverse cis-regulatory sequence motifs predicted in this study have not been previously documented. The 1,215 and 2,225 bp 5′-flanking regions of StPN03 (derived from StPN02) and StPK01, respectively, were used in generating patatin promoter–GUS gene fusions for assessment of promoter activities in potato. Under field conditions, both StPK01 and StPN03 promoters showed tuber-specificity. The former was significantly stronger than the latter as examined by histochemical and fluorometric β-glucuronidase assays. Under in vitro conditions, these promoters were highly inducible by sucrose in stems and leaves. Apart from the applied aspects of this research, this study may help in unraveling the molecular mechanisms involved in the regulation of patatin gene expression.