ibclogo XVI International Botanical Congess


Abstract Number: 3526
Poster No. = 2122


CYTOKININ PRODUCTION BY METHYLOBACTERIUM SPP. LEAF ISOLATES


Robbin Long, Roy Morris, Joseph Polacco, Dept. of Biochemistry, University of Missouri, Columbia, MO 65211 USA


Pink-pigmented facultative methylotrophic bacteria (PPFMs), Methylobacterium spp., are persistent colonizers of plant leaves. Using immunoaffinity and HPLC purification, we isolated 22-111 ng/L trans-zeatin from spent medium of four PPFM leaf isolates and a Methylobacterium extorquens type culture. We identified the isolated zeatin as the trans isomer by RIA with specific monoclonal antibodies and by chromatographic retention times. This was further confirmed by mass spectrometry. Variable amounts of trans-zeatin riboside were also recovered. Incorporation of [3H]adenine into trans-zeatin occurred early in batch culture, remaining relatively constant throughout. Hydrolyzed PPFM tRNA contained zeatin riboside, as did that from the plant symbiont Bradyrhizobium japonicum. No hydroxylated cytokinins were found in E. coli tRNA.


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