Symbiosis‐related polypeptides associated with the early stages of ectomycorrhiza organogenesis in birch (Betula pendula Roth)

SUMMARY As a preliminary step towards elucidation of the molecular basis of ectomycorrhiza differentiation, polypeptide changes at different stages of mycorrhiza development were analyzed in birch (Betula pendula Roth). Time‐sequencing of the stages in the infection process of clonal plants inoculated with a compatible isolate of Paxillus involutus Batsch revealed that by 8 d mature ectomycorrhizas were obtained. Total phenol‐extracted proteins of roots during the ‘mycorrhiza formation stage’ (2–8 d post‐inoculation) were separated by two‐dimensional polyacrylamide gel electrophoresis and the resulting patterns compared with non‐mycorrhizal roots and mycelium. Alteration in the concentration of polypeptides from the host plant roots was limited even after 8 d of contact between the symbionts. However, seven novel polypeptides were detected 4 d after inoculation, three of them being already present in 2‐d‐old ectomycorrhizas. These findings demonstrate that symbiosis‐related polypeptides accumulate in ectomycorrhizal roots prior to any of the morphological changes characterizing the symbiotic state.