Dynamics of cytoskeletal proteins in developing pine ectomycorrhiza

Mycorrhizal short roots of Pinus contorta Dougl. ex Loud colonized by Suillus variegatus (Sow. ex Fr.) O. Kuntze or Paxillus involutus (Batsch) Fr. were collected 1->60 days after fungal contact. The proteins of the inoculated roots were extracted, electrophoretically separated, blotted and immunostained for alpha-tubulin and actin. The development of the mycorrhiza was also followed microscopically. The signal of plant alpha-tubulin was stronger than the signal of fungal alpha-tubulin during the first 5 days in S. variegatus mycorrhiza and was then exceeded by fungal alpha-tubulin. This correlated well with the increase of fungal mycelium in the mycorrhiza. A transient drop in both plant and fungal alpha-tubulin signals was observed 20 days after fungal contact, suggesting a change in the metabolism of the mycorrhiza. The signals for plant and fungal actins in the mycorrhiza increased steadily during early infection and then remained at a high level as the mycorrhiza matured. Similar trends were observed in P. contorta-P. involutus mycorrhiza. The data from P. contorta-S. variegatus mycorrhizas suggests that alpha-tubulin is a growth-related protein, subject to changes, while the amount of actin reflects the general metabolic activity of the mycorrhiza. In both mycorrhizal systems clear alpha-tubulin and actin signals were detected 60 days after colonization, which indicates that the mycorrhizas were metabolically active in spite of their withered appearance.