Abstract
Transgenic tobacco (Nicotiana tabacum var. SR1) plants overexpressing GDP-mannose pyrophosphorylase (GMPH) or GDP-mannose-3',5'-epimerase (GME) were obtained using cDNA sequences from peach fruit. Overexpression of the RNA from the transgene was confirmed, whereas corresponding protein content was increased only by up to 30 % to the nontransformed plants. Asc content in leaves were similar level to the control. Enzyme activity measurement revealed about 2-fold increase of GMPH activity was observed by feeding [14C]-labeled GDP-mannose. On the other hand, due to a difficulty in separating GME reaction product, gaining of GME activity in GME-transformed plants could not be confirmed. To investigate further, transgenic tobacco plants harboring one copy of GMPH or GME transgene was selected and crossed. T1 plants having both GMPH- and GME-transgene were selected and are growing in a green house. Overexpression of both transgenes were confirmed by Northan blot analyses, although transgene silencing was observed in some combinations. Asc content in these double overexpressing lines as well as Western blot analysis of the plants will be presented.
