JXB Advance Access published online on March 14, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern030
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RESEARCH PAPER |
Elicitor-dependent expression of the ribosome-inactivating protein beetin is developmentally regulated*

1Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain
2Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Canto Blanco, E-28049 Madrid, Spain
To whom correspondence should be addressed. E-mail: girbes{at}bio.uva.es
BE27 and BE29 are two forms of beetin, a virus-inducible type 1 ribosome-inactivating protein isolated from leaves of Beta vulgaris L. Western blot analysis revealed the presence of beetin forms in adult plants but not in germ or young plants, indicating that the expression of these proteins is developmentally regulated. While beetins are expressed only in adult plants, their transcripts are present through all stages of development. In addition, the treatment of B. vulgaris leaves with mediators of plant-acquired resistance such as salicylic acid and hydrogen peroxide promoted the expression of beetin by induction of its transcript, but only in adult plants. The plant expresses three mRNAs which differ only in their 3' untranslated region. All these observations suggest a dual regulation of beetin expression, i.e. at the post-transcriptional and transcriptional levels. Additionally, total RNA isolated from leaves treated with hydrogen peroxide, which express high levels of active beetin, is not de-adenylated by endogenous beetin, nor in vitro by the addition of BE27, thus suggesting that sugar beet ribosomes are resistant to beetin.
Key words: Beetin, Beta vulgaris, hydrogen peroxide, ribosome-inactivating protein (RIP), salicylic acid, 3' UTR
* The authors dedicate this article to the beloved memory of Enrique Méndez who passed away on 23 July 2007.
Received 16 October 2007; Revised 17 January 2008 Accepted 21 January 2008