S217Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S215–S223

duction pathway responsible for the recognition of both Nodfactor and Myc factor. Repetitive oscillations in cytosoliccalcium in root hair cells are one of the earliest plant responsesto Nod factor and Myc factor, however the structure of thecalcium response differs for these two signals. These calciumresponses are embedded in the conserved symbiosis signallingpathway with a calcium/calmodulin dependent kinase(CCaMK) being apparently responsible for decoding bothMyc factor and Nod factor induced calcium oscillations. Gain offunction mutations in CCaMK activate nodulation without theneed for Nod factor or rhizobial elicitation. This gain of functionrequires the activity of NSP1, NSP2 and ERN, all transcrip-tional activators. NSP1, NSP2 and ERN have specific functionsin Nod factor signalling and represent a nodulation specificbranch downstream of CCaMK. We propose that Nod factorinduced calcium oscillations that occur in both the cytosol andthe nucleus regulate the DMI3 kinase through a combination ofcalcium and calmodulin binding. DMI3 activates downstreamcomponents, including the transcriptional regulators NSP1,NSP2 and ERN. CCaMK must be able to discriminate betweenthe Nod factor and Myc factor induced calcium oscillations andwe presume that equivalent mycorrhizal specific componentsare induced under the appropriate conditions.

doi:10.1016/j.cbpa.2007.01.471

P1.8Polyketides and Pks genes in lichen-forming fungi: Theimpact of algal transfer metabolites (polyols and glucose)on the production of “lichen substances”

E. Stocker-Wörgötter, (University of Salzburg, Austria)

Lichen-forming, ascomycetous fungi produce a broad spectrumof unique (only found in lichens!) and also common polyketides(pigments, occurring in several classes of fungi and also inhigher plants). In summary, more than 1000 different lichenmetabolites have been chemically identified. The majority ofthem are aromatic and aliphatic polyketides (including a fewlarge ring compounds — macrolides). Lichen metabolites havebeen screened by TLC and HPLC analyses; for a considerablenumber of them a strong biological activity has been recognised.One major objective of our research is to localise Pks genes bystudying under which conditions a particular class of polyketides(e.g., depsides, depsidones, dibenzofurans, anthraquinones, etc.)is expressed in aposymbiotically cultured mycobionts. Inextensive test series, it was shown that the compositions of thenutrient media (contents of algal transfer carbohydrates, “sym-biosis products”) influence and promote the expression ofparticular polyketides (e.g., depsides, depsidones, xanthones) inculturedmycobionts, compounds hitherto known only from intactlichens. It was repeatedly found that stable culture conditions ledto the biosynthesis of fatty acids in form of fat droplets depositedon the surface of the mycelia, whereas “environmental stress”caused a switch from fatty acid to polymalonate pathway and

production of typical polyketides. The impact of the photobiontsand their transfer metabolites on the production of polyketideswill be discussed by comparing several “symbiotic systems”, di-partite, tri-partite and multiple partnerships among lichens andtheir in vitro resynthesis products.For one anthraquinone-producing lichen a gene bank for pkswas successfully established.Progress in understanding the function of fungal type I Pksesand their control by Pks genes may revolutionise the use oflichens/cultured mycobionts in future biotechnologicalapproaches, including heterologous expression of lichen pksgenes in fast growing hosts and also the design of novelbiological active molecules for pharmaceutical applications.

doi:10.1016/j.cbpa.2007.01.472

P1.9Interactions between insects and their symbioticmicroorganisms

A. Douglas, (York University, Canada)

Obligate microbial symbionts are widespread or universal inseveral insect orders and include major agricultural or medicalpests, e.g. blood-feeding lice, bedbugs and tsetse-fly, and plantsap-feeding aphids, planthoppers and whitefly. Our excellentunderstanding of the nutritional and protective roles ofsymbiotic microorganisms in insects has obtained from studiesof the impact of antibiotic treatments (which eliminate thesymbionts) on insect performance and physiology. Theincreasing availability of genome sequence data for themicrobial symbionts and their insect insects provides newopportunities to address symbiotic interactions at the molecularlevel. I will explore the routes by which physiology andgenomics are being integrated to obtain an understanding ofinsect interactions with their beneficial microorganisms, and toidentify novel strategies in insect pest management.

doi:10.1016/j.cbpa.2007.01.473

P1.10Signalling of gene expression in rhizosphere bacteria —Iron in the soil and sulphur in the seas

A. Johnston, J. Todd, R. Rogers, N. Nikolaidou-Katsaridou,S. Li, A. Curson, (University of East Anglia, Norwich, UnitedKingdom)

Nitrogen fixing legume root nodules are full of iron— the plant-encoded leghaemoglobin and the bacterial nitrogenase andancillary electron donors are all iron-containing proteins.Although we do not know the major sources of Fe for rhizobiain nodules, Fe acquisition by free-living rhizobia, in the soil andin the rhizosphere, has some unusual features. They have a wider