Transgenic Root Nodules ofVicia hirsuta:A Fast and Efficient System for the Study of Gene Expression in Indeterminate-Type Nodules

The Agrobacterium rhizogenes-mediated transformation of Vicia hirsuta resulted in the induction of transgenic 'hairy roots' on wounded epicotyls of young seedlings. As soon as the 'hairy roots' had developed enough, the original wild-type roots were excised and composite plants were thus established that consisted of transgenic roots on untransformed shoots. The proportion of roots that proved by their beta-glucuronidase (GUS) expression to be transgenic reached 88%. The inoculation of composite plants with Rhizobium leguminosarum bv. viciae led to the induction of transgenic indeterminate-type root nodules in less than 20 days after the V. hirsuta seedlings had been infected with A. rhizogenes. The structure and the function of the transgenic nodules were comparable to that of wildtype nodules. To illustrate the applicability of the system, the spatial and temporal expression pattern of an intron-containing p35S-gusA-int gene fusion was monitored during root and nodule development.