Development of transgenic cucumber expressing TPSP gene and morphological alterations

To develop transgenic cucumber tolerant to abiotic stress, a cotyledonary-node explants were co-cultivated with Agrobacterium tumefaciens (EHA101) carrying TPSP gene (pHC30-TPSP). After transfer to fresh medium every two week for eight weeks, putative transgenic plants were selected when shoots grown a length greater than 3 cm from the cotyledonary-node explants on selection medium supplemented with $5\;mgl^{-1}$ phospinotricin as selectable agent. The confirmation of transgenic cucumber was based on the Northern blot analysis. Thirty four shoots (5.2%) with resistance to phospinotricin were obtained from 660 explants inoculated. Of them, transformants were only confirmed from 11 plants (1.7%). Transgenic cucumber expressing TPSP gene was more synthesized at 3.8 times amounts of trehalose (0.014 mg g fresh $wt^{-1}$) than non-transformants (0.0037 mg g fresh $wt^{-1}$). However, all of transgenic plants showed abnormal morphology, including stunted growth (< height 15 cm), shrunken leaves, and sterility as compared with non-transgenic plants (> height 150 cm) under the same growth environment. These results lead us to speculate that the overproduction of trehalose was toxic for cucumber, even though that had known for rice as non-toxic.