Composite Actinorhizal Plants with Transgenic Roots for the Study of Symbiotic Associations with Frankia
Figure 1
β-glucuronidase expression in hairy roots of AUX1-GUS C. glauca plants silenced with a RNAi-CgSymRK construct. AUX1-GUS plants were obtained after genetic transformation with the strain of A. tumefaciens C58C1 as described in [50], and transgenic shoots were then inoculated with a strain of A. rhizogenes A4RS containing either an empty vector (a) or a vector with a 35S-CgSymRK-hairpin construct to downregulate the expression of the receptor-like kinase gene SymRK from C. glauca (b, c) [51]. Composite plants were screened for GFP expression, inoculated with Frankia, and β-glucuronidase gene expression was studied in 50 μm three-week-old nodule sections. (a) In nonsilenced nodules, AUX1-GUS expression was observed in the nodule vascular system, the nodule apical zone at the basis of the nodular root, in the Frankia infected cells, and in the phellogen. (b, c) In the RNAi-CgSymRK nodules from two different composite plants, AUX1-GUS expression was found to be strongly affected; a strong alteration of the nodule size correlated with a low residual activity of the reporter gene (c). Bars: a = 1 mm, b = 500 μm, and c = 250 μm.
