Article

Plant Growth Regulation

, Volume 15, Issue 3, pp 271-279

Gibberellin-photoaffinity labeling of wild oat (Avena fatua L.) aleurone protoplasts

  • Robert P. WalkerAffiliated withDepartment of Agricultural Sciences, University of Bristol, 1 ACR Long Ashton, Long Ashton Research Station
  • , Wanda M. WaterworthAffiliated withDepartment of Agricultural Sciences, University of Bristol, 1 ACR Long Ashton, Long Ashton Research Station
  • , Michael H. BealeAffiliated withDepartment of Agricultural Sciences, University of Bristol, 1 ACR Long Ashton, Long Ashton Research Station
  • , Richard HooleyAffiliated withDepartment of Agricultural Sciences, University of Bristol, 1 ACR Long Ashton, Long Ashton Research Station

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Abstract

Aleurone protoplasts of wild oat (Avena fatua L.), and subcellular fractions isolated from them, were photoaffinity labeled using the synthetic gibberellin (GA) derivative GA4-17-yl-1′-(1′-thia)propan-3′-ol-4-azido-5-[125I]iodosalicylate. Labeled polypeptides were identified by electrophoresis under denaturing conditions followed by autoradiography. GA-photoaffinity labeling of both intact protoplasts and isolated subcellular fractions led to the covalent attachment of the reagent to many polypeptides. A 50 kD polypeptide in the soluble fraction of homogenates of aleurone protoplasts GA-photoaffinity labeled in vivo showed specific binding. The biologically active GA1, GA4 and GA4-17-yl-1′(1′-thia)propan-3′-ol-4-azidosalicylate completed for binding whereas the biologically inactive GA8 and GA34 did not. The GA-photoaffinity labeling characteristics of this polypeptide suggested that it might interact specifically with biologically active GAs in vivo. Attempts to detect specific GA-binding in in vitro GA-photoaffinity labeling experiments met with only limited success perhaps indicating the labile nature of specific binding observed in vivo. The potential of GA-photoaffinity labeling for identifying GA-binding proteins in aleurone and other GA-responsive tissues is discussed.

Key words

α-amylase Avena fatua gibberellin-binding proteins gibberellins Gramineae photoaffinity wild oat