Analysis of a chimeric class-I patatin-GUS gene in transgenic potato plants: High-level expression in tubers and sucrose-inducible expression in cultured leaf and stem explants
AbstractFructans are polymers of fructose that are present as storage carbohydrates in various plants. Jerusalem artichoke (Helianthus tuberosus L.) contains a high amount of inulin. Two enzymes are involved in inulin biosynthesis. The sucrose:sucrose 1-fructosyltransferase (1-SST) enzyme mainly catalyzes the synthesis of 1-kestose from sucrose. In the next step, fructan:fructan 1-fructosyltransferase (1-FFT) catalyzes the synthesis of inulin from 1-kestose. In this study, the Ht1-SST and Ht1-FFT genes were isolated from Jerusalem artichoke and expressed in potato (Solanum tuberosum L.), either separately or together, via Agrobacterium-mediated transformation. Transgenic potato tubers overexpressing Ht1-SST accumulated 1-kestose to a high level (up to 3.36 mg/g), while tubers overexpressing both Ht1-SST and Ht1-FFT accumulated up to 3.14 mg/g short-chain inulin-type fructans, with the degree of polymerization (DP) ranging from 3 to 5, excluding high DP inulins. Transgenic potato plants accumulated fructo-oligosaccharides to a high level, following the fructan biosynthetic pathway of Jerusalem artichoke, and therefore present a high potential for the mass production of inulin through established potato breeding and cultivation methods.
Resistance to Potato mop-top virus (PMTV) was studied in Nicotiana benthamiana and potato (Solanum tuberosum cv.<br />Saturna) transformed with the coat protein (CP) gene of PMTV. In N. benthamiana plants mechanically inoculated with<br />PMTV, RNA2 was detected in leaves and roots in several plants in the absence of RNA3. When N. benthamiana was<br />grown in infested soil, viral RNA was detected in roots, but no systemic movement of PMTV to above-ground parts was<br />observed. The incidence of PMTV infections was reduced in the CP-transgenic potato plants grown in an infested field<br />in Sweden. However, in infected tubers, all three virus RNAs were detected.
Expression of Jerusalem artichoke (Helianthus tuberosus L.) fructosyltransferases, and high fructan accumulation in potato tubers