Nodule formation kinetics exhibited by the nodPQ mutant harboring plasmid-borne nodPQ. Sterile L. japonicus seedlings were cultured on B&D agar slants containing 40 nM AVG. Plants were inoculated 48 h after transfer to B&D agar slants with either wild-type M. loti, wild-type M. loti harboring either empty vector (GTO015) or pGTO101 (GTO016), the nodPQ mutant or the nodPQ mutant harboring either empty vector (GTO108) or pGTO101 (GTO101), or sterile 10 mM MgSO4. (A) At various intervals following inoculation the plants were analyzed and the number of nodules was counted as described in Materials and Methods for wild-type M. loti (wt), GTO015, GTO016, the nodPQ mutant, GTO108, GTO101, or sterile 10 mM MgSO4. (B) Plants were harvested at 120 days postinoculation, and their dry weight was measured. Lane 1, wild-type M. loti; lane 2, GTO015; lane 3, GTO016; lane 4, nodPQ; lane 5, GTO108; lane 6, GTO101; lane 7, sterile 10 mM MgSO4.