S263Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S255–S266

our present study was to explore whether nitric oxide couldcontribute to Cd toxicity in A. thaliana. Under Cd challenge, asignificant NO synthesis was detected both in roots and leaves.Cd-induced NO synthesis was reduced by the mammalian nitricoxide synthase (NOS) inhibitors L-NAME and PBITU but wasstill observed in the Atnos1mutant, suggesting the occurrence ofa NOS-like enzyme distinct from AtNOS1. A phenotypeanalysis of Cd-treated plants grown in presence of L-NAMEhighlights a role for NO in mediating toxicity of the metal.Accordingly, using inductively coupled plasma-atomic emissionspectrometry (ICP), we provided evidences that NO is requiredfor Cd assimilation in roots. To investigate the molecularmechanisms underlying this effect, a micro-array approach wasperformed. Several gene candidates whose products mightcontribute to Cd root absorption through a NO-dependentprocesses were identified. These genes include nicotianaminesynthase, a gene previously related to Cd hyper-accumulation.Other genes might be related to NO ability to promote Cdtoxicity.

doi:10.1016/j.cbpa.2007.01.665

P5.26Unusual expression patterns of SODs in rice

N. Tsakirpaloglou, A. Kohli, A. Gatehouse, (University ofNewcastle)

Rice genome sequencing and annotation render this crop asuitable model for other cereals. Reactive oxygen species(ROS) are by-products of specific metabolic reactions inplants. Although ROS are known to impair cellular biomole-cules, they are also necessary for signal transduction duringdevelopment and stress response. The differential constitutiveand induced expression of superoxide dismutases (SODs) playsa critical role in scavenging the superoxide radical. In addition,SOD plays a critical role in plant growth, flowering andfruiting, senescence and stress response. A total of 8 SODgenes have been annotated in the sequenced rice genome todate, encoding manganese (MnSOD), iron (FeSOD) andcopper-zinc (Cu-ZnSOD). To understand differential expres-sion of the annotated SOD isogenes, we sought to characterisetheir upstream cis-regulatory elements. In pilot studies weobserved 10–15 independent bands for SOD activity in ricethrough native polyacrylamide gel electrophoresis. The numberof bands and/or their intensity varied depending on a) the planttissue; b) the developmental stage; c) nutrient stress; d)application of 5-azacytidine. However, in each case more thanthe predicted 8 bands were observed. These additional bandscan be generated by a) different categories of alternativesplicing; b) different denominations of multimers; c) post-translational protein modifications; d) novel SOD isogenes.Characterisation of these additional bands is an important stepto understanding whether they represent novel isoforms ofknown proteins or novel proteins per se. Furthermore, the

present study will provide the basis for functioning of redoxgenes in rice.

doi:10.1016/j.cbpa.2007.01.666

P5.27Secondary metabolites: Tools for stress protection in plants

V. Velikova, A. Edreva, T. Tsonev, E. Gesheva, (Institute ofPlant Physiology-Sofia); S. Dagnon, (Tobacco and TobaccoProducts Institute-Plovdiv); F. Loreto, (CNR-Roma); A. Gürel,(Aegean University); H. Jones, (University of Dundee)

The protective role of secondary metabolites against environ-mental constraints is substantiated by studying various plant-abiotic stress stimuli systems. It was shown that phenylamides,conjugates of hydroxycinnamic acids and polyamines, areinduced in tobacco and bean leaves, subjected to water excessand heat shock, respectively. Reactive oxygen species (ROS)-scavenging ability of phenylamides was evidenced. Anthocya-nins were found to dramatically accumulate in cotton leaves dueto Na/K unbalance; shifts from mono- to orthodihydroxysubstitution in the B-ring of anthocyanin aglycone wasestablished, with this conferring a higher ROS-scavengingcapacity of the molecule. The protective effect of a gaseoussecondary metabolite, isoprene (2-methylbutadiene), emitted byPhragmites australis plants against ozone fumigation and heatshock was shown. The ROS-scavenging ability of isoprene wasdemonstrated. Altogether, the data provide evidence thatsecondary metabolites, irrespective of their chemical type andplant origin, can be involved in non-enzymatic plant defensestrategy by their antioxidant and antiradical properties.

doi:10.1016/j.cbpa.2007.01.667

P5.28Isoprene-induced protection in tobacco plants exposed toelevated ozone concentration

C. Cojocariu, N. Hewitt, (Lancaster University); C. Vickers, P.Mullineaux, (University of Essex); V. Velikova, (BulagarianAcademy of Sciences)

Isoprene (C5H8) is synthesised and emitted by many plantspecies in high amounts but the reason for this apparent carbonloss has yet to be clarified. It has been proposed that isoprenemight be involved in plant protection against oxidative damage.In this work, we tested if isoprene synthesis and emission fromplants provide protection against oxidative stress induced byozone. For this, transgenic tobacco plants over-expressing apoplar isoprene synthase gene under the control of the CaMV35S promoter were generated. Several of these lines emittedisoprene at levels equivalent to that observed in poplar. These