The effects of mutations in nolL and nodZ genes of Bradyrhizobium sp. WM9 [Lupinus] upon root nodule ultrastructure in Lupinus luteus L.

In Lupinus luteus L. - Bradyrhizobium sp. WM9 (Lupinus) symbiosis, mutations in nolL and nodZ genes (no fucose or no acetyl group at the fucose) did not hinder nodule morphogenesis significantly. The effects of both mutations, as observed in nodule anatomy and ultrastructure, were the same. The mutations affected the early stage of symbiosome population formation and thus the differentiation of bacteroid tissue. In mutant-inoculated plants, the bacteroid tissue developed more cell-wall-associated bacterial enclaves. Also, the disappearance of vesicles accumulating cell- wall-like material was delayed. The symptoms of mutations were transient and the plants recovered from the initial nitrogen starvation.