Mechanism of action of Rhizobium nod factors

• Research unit: EU RFP
• Project number: 97.0247

Key words (English)

Lateral root primordium; rice; expansin; flavonoids

Alternative project number (English)

EU project number: FMRXCT980243

Research programs (English)

EU-programme: 4. Frame Research Programme - 10.1 Stimulation of training and mobility

Short description (English)

See abstract

Partners and International Organizations (English)

Bisseling/Gadella, Wageningen (NL); Barker/Cullimore, Tolouse (F); Baue/Prome, Tolouse (F); Bowler, Napels (I); Downie, Norwich, (UK); Felle, Giessen (D); Hirt, Vienna (A); Holsters, Gent (B); Kondorosi, Gif (F); Marker/Oestergaard, Aarhus, (DK); Schmidt, Cologne (D); Spaink, Leiden (NL)

Abstract (English)

Within the network we try to develop a heterologous expression system in a cereal model plant. Initiation of cell division is a very basic element which nodulation and lateral root development have in common. In rice, lateral roots arise from pericycle cells located adjacent to a phloem pole. We characterise the initial stages of lateral root development in rice. A comparison between lateral root and nodule formation showes that similar patterns of GH3:gusA expression, chalcone synthase gene expression, and accumulation of a particular flavonoid compound occurred in the cortical cells involved in both processes. We examined the localization of flavonoids in the lateral root emerging zone of rice roots. Using the confocal laser scanning microscope the strong fluorescence was localized in the outer cell layer of growing primordia. In cells the fluorescence signals were detected in cytoplasm. It has been shown that local changes in flavonoid accumulation could regulate local auxin levels during nodule organogenesis. A similar mechanism could be involved in lateral root formation. The auxin treatment altered the distribution of fluorescence signal in lateral root primordia. The fluorescence was not localized in the outer cell layer of growing primordia. The flavonoids were present in cells but the fluorescence signal was restricted to vacuoles and not detectable in the cytoplasm similar to non-treated roots. Lateral root formation is accomplished by a combination of cell divisions and cell expansion. During organ formation, expansin may function both as a factor triggering organogenesis and as a factor sustaining growth of the organ The distribution pattern of expansins Os-EXP2 and Os-EXP3 mRNA in rice lateral root was analysed by in situ hybridization. Antisense riboprobes for both expansins Os-EXP2 and Os-EXP3 showed hybridization in cells of lateral root primordia and in growing young lateral roots.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0247