Transgenic apple plants overexpressing the chalcone 3-hydroxylase gene of Cosmos sulphureus show increased levels of 3-hydroxyphloridzin and reduced susceptibility to apple scab and fire blight

Main conclusionOverexpression of chalcone-3-hydroxylase provokes increased accumulation of 3-hydroxyphloridzin inMalus. Decreased flavonoid concentrations but unchanged flavonoid class composition were observed. The increased 3-hydroxyphlorizin contents correlate well with reduced susceptibility to fire blight and scab.The involvement of dihydrochalcones in the apple defence mechanism against pathogens is discussed but unknown biosynthetic steps in their formation hamper studies on their physiological relevance. The formation of 3-hydroxyphloretin is one of the gaps in the pathway. Polyphenol oxidases and cytochrome P450 dependent enzymes could be involved. Hydroxylation of phloretin in position 3 has high similarity to the B-ring hydroxylation of flavonoids catalysed by the well-known flavonoid 3′-hydroxylase (F3′H). Using recombinant F3′H and chalcone 3-hydroxylase (CH3H) from Cosmos sulphureus we show that F3′H and CH3H accept phloretin to some extent but higher conversion rates are obtained with CH3H. To test whether CH3H catalyzes the hydroxylation of dihydrochalcones in planta and if this could be of physiological relevance, we created transgenic apple trees harbouring CH3H from C. sulphureus. The three transgenic lines obtained showed lower polyphenol concentrations but no shift between the main polyphenol classes dihydrochalcones, flavonols, hydroxycinnamic acids and flavan 3-ols. Increase of 3-hydroxyphloridzin within the dihydrochalcones and of epicatechin/catechin within soluble flavan 3-ols were observed. Decreased activity of dihydroflavonol 4-reductase and chalcone synthase/chalcone isomerase could partially explain the lower polyphenol concentrations. In comparison to the parent line, the transgenic CH3H-lines showed a lower disease susceptibility to fire blight and apple scab that correlated with the increased 3-hydroxyphlorizin contents.Austrian Sci-ence Fund (FWF

Kulturlandschaften zwischen Schutz und Nutzung Planungsmodelle einer nachhaltigen Freiraum- und Landschaftsentwicklung

'Das Heft enthaelt den Abschlussbericht des von Mitte 1996 bis Ende 1998 am IRS bearbeiteten Forschungsprojektes 'Modellhafte Planungsansaetze einer nachhaltigen Freiraum- und Landschaftsentwicklung'. Dabei geht es um die Frage, wie die vom Menschen in langen Zeitlaeufen geformte Kulturlandschaft als integraler Bestandteil der menschlichen Umwelt erhalten und weiterentwickelt werden kann - und dies fokussiert auf die Frage 'Schutz oder Nutzung' bzw. die von den Verfassern vertretene Haltung 'Schutz durch Nutzung'. Expliziert wird diese Frage an drei spezifisch angelegten Fallstudien im Land Brandenburg. Am Beispiel von zwei Regionalparks am Stadtrand von Berlin (Teltow-Park und Mueggel-Spree-Park), dem Biosphaerenreservat Schorfheide-Chorin in der peripheren laendlichen Region der Uckermark und dem Seeufer- und Wochenendhauskonzept der Stadt Neuruppin werden jeweils die Chancen und Restriktionen der planerischen Umsetzung einer nachhaltigen Freiraum- und Landschaftsentwicklung empirisch analysiert. Dabei gilt das besondere Augenmerk dem Einsatz kooperativer Planungselemente, dem Umgang mit Konflikten im Planungsprozess, der Akzeptanz durch die Adressaten der Planung sowie den Erfolgen und Defiziten im Prozess der Umsetzung.' (irs)SIGLEAvailable from UuStB Koeln(38)-990106390 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Degradation of glutathione S-conjugates by a carboxypeptidase in the plant vacuole

Wolf AE, Dietz K-J, Schröder P. Degradation of glutathione S-conjugates by a carboxypeptidase in the plant vacuole. FEBS Letters. 1996;384(1):31-34.For plants, glutathione conjugation is a major pathway to detoxify organic xenobiotic. Glutathione S-conjugates (SG-conjugates) are formed in the cytosol, the in vitro transport over the tonoplast has been described and a final storage in the vacuole has been postulated. We show here that alachlor rapidly accumulates as GS-conjugates in the plant vacuole and that the first step of its degradation, the formation of the respective gamma-glutamylcysteinyl-S-conjugate, is catalyzed by a vacuolar carboxypeptidase, These results suggest the glutathione conjugate as a transport form but not a storage form of xenobiotic molecules