TRANSFORMATION OF POTATO PLANTS WITH THE ISOPENTENYLTRANSFERASE GENE LEADS TO ENHANCED STOLON DEVELOPMENT AND PRECOCIOUS TUBER SPROUTING

Abstract

This study was conducted to show the effect of transformation of potato (Solanum tuberosum) plants with the isopentenyltransferase (ipt) gene on plant morphology and cytokinin levels in leaves and tubers. The ipt gene, which catalyzes the rate-limiting step of the cytokinin synthesis pathway, was placed under the control of a tuber-specific patatin promoter and introduced into potato plants (cv. Norchip) via Agrobacterium-mediated transformation. The presence of the ipt gene in transgenic potato plants was confirmed by Southern hybridization. Shoot morphology was normal in nearly all transgenic plants prior to and after tuberization. Transgenic plants had extensive stolon growth and an increased number of tubers. Premature sprouting of tubers and an increase in the number of sprouts were also observed in transgenic plants. Total fresh and dry weight of tubers was similar in control and transgenic plants. Expression of the ipt gene was tuber specific, as determined by northern hybridization and cytokinin analysis. The concentration of zeatin and zeatin riboside was increased in tubers of transformed plants, but the level in source leaves was similar in transformed and control plants. This study supports a role for cytokinin in tuber initiation and release of dormancy.