Poster: Hormones
Abs #
574: A trans-zeatin riboside and other compounds in root xylem sap negatively regulates adventitious root formation on cucumber hypocotyls
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Presenter: |
Kuroha, Takeshi , tkuroha@sakura.cc.tsukuba.ac.jp |
Authors | Kuroha, Takeshi (A) Kato, Hisashi (B) Asami, Tadao (B) Yoshida, Shigeo (B) Kamada, Hiroshi (A) Satoh, Shinobu (A) | | Affiliations: |
(A): University of Tsukuba, Institute of Biological Sciences
(B): RIKEN (The Institute of Physical and Chemical Research)
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For the elucidation of the physiological functions of the substances in xylem sap, we investigated the biological activities of xylem sap substances using a shoot culture of cucumber. When the hypocotyl of cucumber seedling was cultured in the fractions of xylem sap collected from squash roots, inhibition of the formation of adventitious roots from the hypocotyl was observed. The formation of adventitious roots on the stems and hypocotyls is thought to be controlled negatively by the inhibitors produced by roots in addition to the promotion by auxins produced by shoots. Therefore, we attempted to identify the inhibitors for the formation of adventitious roots using double-solvent extraction, normal and reverse phase chromatography and liquid chromatography / tandem mass spectrometry (LC/MS/MS).
As a result, we identified trans-zeatin riboside (ZR) as an active substance in the inhibitory fraction of xylem sap. The concentration of ZR in xylem sap is estimated to be 2 x 10-8 M. Application of ZR at concentrations from 3.16 x 10-9 M inhibited the adventitious root formation. Another predominant inhibitory activity seems to be due to trans-zeatin (Z) in xylem sap. However, the concentration of Z in the xylem sap was insufficient to inhibit the formation of adventitious roots. These results suggest that ZR plays a role as an endogenous suppressor in the formation of adventitious roots in plant. Because weaker inhibitory activities were also observed in the other fraction obtained from HPLC experiment, it is possible to speculate that substances other than ZR have auxiliary roles in the negative regulation of adventitious root formation; these remain unidentified.
