Influence of mutation in pea (Pisum sativum L.) cdt (cadmium tolerance) gene on histological and ultrastructural nodule organization

Abstract

Background. A comparative analysis out of the structural organization of the symbiotic nodules of the pea initial line SGE and the mutant line SGECdt, characterized by increased tolerance to cadmium and increased its accumulation, was carried out.
 Materials and methods.Nodules of initial line SGE and mutant SGECdt were analyzed using light and transmission electron microscopy.
 Results. The non-treated nodules of SGE and SGECdt were characterized by a similar histological and ultrastructural organization. In the nodules of SGE exposed to 100 M CdCl2 in infected cells, the following abnormalities were observed: expansion of the peribacteroid space, destruction of the symbiosome membrane, fusion of symbiosomes and, as a result, the formation of symbiosomes containing several bacteroids. In the nodules of SGECdt, infected cells did not undergo pronounced changes. In the nodules of SGE exposed to 1 mM CdCl2, at the base of the nodule, senescent infected cells with completely destroyed cytoplasm and degrading bacteroids appeared. Also there were present cells in which the contents of symbiosomes were lysing, and only the ghosts of the bacteroids remained in them. In SGECdt, in some infected cells, abnormalities were manifested in an increase in the peribacteroid space, partial destruction of symbiosome membranes, fusion of symbiosomes, and release of bacteroids into the vacuole.
 Conclusions. The tolerance of pea nodules to cadmium can be significantly increased due to a single recessive cdt mutation.