Dynamics of cytoskeletal proteins in developing pine ectomycorrhiza

Abstract:
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.