Analysis of GDP-D-mannose pyrophosphorylase gene promoter from acerola (Malpighia glabra) and increase in ascorbate content of transgenic tobacco expressing the acerola gene.

GDP-D-mannose pyrophosphorylase (GMP) is an important enzyme in the Smirnoff-Wheeler's pathway for the biosynthesis of ascorbic acid (AsA) in plants. We have reported recently that the expression of the acerola (Malpighia glabra) GMP gene, designated MgGMP, correlates with the AsA content of the plant. The acerola plant has very high levels of AsA relative to better studied model plants such as Arabidopsis. Here we found that the GMP mRNA levels in acerola are higher than those from Arabidopsis and tomato. Also, the transient expression of the uidA reporter gene in the protoplasts of Nicotiana tabacum cultures showed the MgGMP gene promoter to have higher activity than the cauliflower mosaic virus 35S and Arabidopsis GMP promoters. The AsA content of transgenic tobacco plants expressing the MgGMP gene including its promoter was about 2-fold higher than that of the wild type.