Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

POLYAMINE BIOSYNTHETIC GENE EXPRESSION IN ARABIDOPSIS THALIANA AND EFFECT OF DIFFERENT STRESSES

FORNALÈ S.*, RUIZ CARRASCO K.B.*, TASSONI A.L.*, FRANCESCHETTI M.**, BAGNI N.*

* Dipartimento di Biologia Ev. Sper. e Centro Interdipartimentale per le Biotecnologie, Università di Bologna, Via Irnerio 42, 40126 Bologna, Italy

** Division of Food Safety Science, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK

Arabidopsis thaliana, polyamines, stress

The aliphatic polyamines putrescine, spermidine and spermine are involved in several plant processes such as cell division, floral buds development, fruit ripening and stress responses. Nevertheless the mechanism underlying their action has still to be unravelled. Plants synthesise putrescine by means of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), while spermidine is produced through the addition of an aminopropylic moiety to putrescine, reaction that requires the enzyme spermidine synthase (Spd Synt) and S-adenosyl decarboxylase (SAMDC). Spermine is synthesised by the addition of a further aminopropylic moiety to spermidine, step that requires the action of SAMDC and spermine synthase (Spm Synt). All these enzymes seem to be regulated at various levels. An antizyme seems to regulate post-translationally the activity of ODC, although a post-transcriptional control can not be excluded. Even in the case of ADC there are evidences in favour of a regulation mechanism acting at multiple levels. Recently two overlapping small ORF have been identified in transcripts encoding SAMDC (Franceschetti et al., 2001) which are likely to be involved in its post translational regulation. Furthermore, some of these enzymes are encoded by two or more genes, and the different isoforms are thought to be differentially localised or at least to have different functions. Aim of our research is to understand the physiological role of these gene families using the model plant Arabidopsis thaliana. This plant has already been used to study polyamine metabolism (Tassoni et al., 2000) and two cDNA coding for ADC, six for SAMDC (only two of which are functional) and two for Spm Synt have been sequenced (Franceschetti et al., 2001). A gene encoding a Spm Synth (ACAULIS5) have been isolated, while all the efforts to isolate an ODC gene have been unsuccessful. Our attempt is to test the effect of different stresses such as osmotic (mannitol), salt (NaCl) and thermal stress on gene expression. Specific primers have been designed in order to discriminate between the different transcript of ADC 1 and 2, SAMDC 1 and 2 and Spd Synth 1 and 2. These will be used to perform a differential analysis by means of semi-quantitative RT-PCR to be confirmed by Northern Blot analysis. At the same time polyamine content and enzyme activities will be determined in control and treated plants.

References:

Franceschetti M., Hanfrey C., Scaramagli S., Torrigiani P., Bagni N., Burtin D. and Michael A.J. (2001), Biochem J 353: 403-405.

Tassoni A., van Buuren M.L., Franceschetti M., Fornalè S., and Bagni N. (2000), Plant Physiol. Biochem. 38: 383-393.