EFFECTS OF REDUCING COMPOUNDS ON AGROBACTERIUM-MEDIATED TRANSFORMATION OF SWEET POTATO

Abstract

Reducing compounds have so far been used for improvement of Agrobacterium-mediated transformation of crop plants with a strong ability to give rise to tissue browning, but not for that of sweet potato. Therefore, we examined the effects of commercially available five reducing compounds (L-ascorbic acid, L-cysteine, dithiothreitol, 2-mercaptoethanol, and reduced glutathione) on parameters associated with Agrobacterium system prior to applying them to sweet potato transformation. The parameters chosen in this study are enzymatic browning caused by sweet potato leaves, callus formation from the leaves and vir gene expression in Agrobacterium. All five reducing compounds restrained acute browning at concentrations of 20-60 mM, of the buffer in which the wound leaves were incubated. However, the reducing compounds except reduced glutathione arrested callus formation from the healthy leaves at 10 mM or less. Thus, we tested whether reducing compounds at these low concentration ranges can suppress tissue browning of sweet potato leaves which is slowly occurred under hygromycin B, and found that all of them failed. Furthermore, the compounds except 2-mercaptoethanol repressed vir gene expression at concentrations of 1-10 mM, which is essential to transfer T-DNA molecules from the bacteria to plant cells. Based on the results, we discuss usage of the reducing compounds on sweet potato transformation.