Activation of the cell cycle machinery and the isoflavonoid biosynthesis pathway by active Rhizobium meliloti Nod signal molecules in Medicago microcallus suspensions

• Published in: The EMBO journal Vol. 13; no. 5; pp. 1093 - 1102
• Main Authors: Savouré, A., Magyar, Z., Pierre, M., Brown, S., Schultze, M., Dudits, D., Kondorosi, A., Kondorosi, E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.03.1994
• Subjects: Biological and medical sciences; CDC2 Protein Kinase - metabolism; Cell Cycle; Cells, Cultured; Cyclins - biosynthesis; Cyclins - metabolism; Fundamental and applied biological sciences. Psychology; Genes, Plant; Genetic Markers; Histones - genetics; In Situ Hybridization; Isoflavones - metabolism; Medicago; Medicago sativa - genetics; Membrane Proteins; Oxidoreductases - biosynthesis; Oxidoreductases - genetics; Oxidoreductases Acting on CH-CH Group Donors; Parasitism and symbiosis; Plant Cells; Plant physiology and development; Plant Proteins - biosynthesis; Plants - genetics; Plants - metabolism; Rhizobium meliloti; Sinorhizobium meliloti - physiology; Symbiosis; Thymidine - metabolism; Callus; Symbiotic relation; Rhizobium meliloti; Medicago sativa; Nodulation; Vegetal microorganism relation; Biosynthesis; Flavonoid; Glycolipid; Signal transduction; Suspension culture; Leguminosae; Dicotyledones; Angiospermae; Cell cycle; Bacteria; Spermatophyta; Rhizobiaceae
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1994.tb06358.x

We have shown that treatment of Medicago microcallus suspensions with the cognate Rhizobium meliloti Nod signal molecule NodRm‐IV(C16:2,S) can modify gene expression both qualitatively and quantitatively. At concentrations of 10(‐6) ‐ 10(‐9) M, this host specific plant morphogen but not the inactive non‐sulfated molecule stimulated cell cycle progression as indicated by the significantly enhanced thymidine incorporation, elevated number of S phase cells, increase in kinase activity of the p34cdc2‐related complexes and enhancement of the level of expression of several cell cycle marker genes, the histone H3‐1, the cdc2Ms and the cyclin cycMs2. The presented data suggest that at least part of the physiological role of the Nod factor may be linked to molecular events involved in the control of the plant cell division cycle. In situ hybridization experiments with antisense H3‐1 RNA probe indicated that only certain cells of the calli were able to respond to the Nod factor. High (10(‐6) M) but not low (10(‐9) M) concentrations of the active Nod factors induced the expression of the isoflavone reductase gene (IFR), a marker gene of the isoflavonoid biosynthesis pathway in most callus cells. Our results indicate that Medicago cell responses to the Nod signal molecules can be investigated in suspension cultures.