Identification of a Benzyladenine Disaccharide Conjugate Produced during Shoot Organogenesis in Petunia Leaf Explants

Prior studies of benzyladenine (BA) metabolism in Petunia hybrida Vilm. leaf explants during shoot organogenesis revealed the presence of an abundant unidentified BA conjugate. The BA conjugate, compound C, made up to 39% of the total pool of BA conjugates in two Petunia lines and was associated with an increased shoot organogenic response when compared with a third Petunia line that did not produce any compound C. Structural analysis of compound C utilizing fast atom bombardment mass spectrometry, two methods of carbohydrate analysis, ultraviolet absorption spectra, and Fourier transform infrared spectra identified it as a new cytokinin conjugate, 6-benzylamino-9-[O-glucopyranosyl-(1-->3)-ribofuranosyl]-purine. Based on our prior biological studies and the similarity of this compound to related cytokinin conjugates, this disaccharide cytokinin conjugate may be part of the interconvertible pool of cytokinins active in Petunia shoot organogenesis.