Iron and reactive oxygen responses in Pinus sylvestris root cortical cells infected with different species of Heterobasidion annosum sensu lato

摘要

Defence mechanisms in trees are not well understood. We assessed whether distribution of iron ions and their co-localisation with reactive oxygen species in Pinus sylvestris root cells reflect differential preferences of the pathogens Heterobasidion annosum sensu stricto,H. parviporum and H. abietinum to the host. Strains of H. annosum s. s. characterised by a greater preference for P. sylvestris induced accumulation of superoxide (O_2 -) in host cells 6 h after inoculation, whereas two peaks in accumulation of O_2 - (after 4 and 48 h) were observed after infection with strains of the pathogens H. parviporum and H. abietinum, which have a lower preference for P. sylvestris. Moreover, strains of H. annosum s. s. caused increased production of hydrogen peroxide (H_2O_2) in P. sylvestris cells, in contrast with strains of the other two species (H. parviporum and H. abietinum). Following inoculation with H. annosum s. s. strains, H_2O_2 was correlated negatively with O_2 - and correlated positively with ferrous iron (Fe~2+). Co-localisation of Fe~3+ with H_2O_2 may suggest that they are involved in inducing hypersensitive responses and eventually cell death in roots inoculated with H. annosum s. s. strains, in contrast with H. parviporum, in which other mechanisms operate when the host is parasitised