Phase- and age-related differences in protein tyrosine phosphorylation in Sequoia sempervirens

Apical and basal halves of 3 cm long apical segments of in vitro cultured juvenile, adult and rejuvenated Sequoia sempervirens shoots were analyzed for total and tyrosine phosphorylated proteins. The latter was detected by a phosphotyrosine specific antibody. Younger tissues, or the apical halves of shoot terminals, showed larger amounts of 36, 44, 46 kDa proteins and lesser amounts of 29 kDa proteins. These are proposed as age-related changes. Phase-related proteins were also evident. Adult tissues contained more of the 34 and 36 kDa proteins than juvenile and rejuvenated shoots. Western blotting with a phosphotyrosine specific antibody revealed more of 25, 39, and 54 kDa protein in the younger tissues. In addition, tyrosine phosphorylated proteins of 25 and 34 kDa were higher in the adult, than in juvenile or rejuvenated tissues. Our findings showed that protein tyrosine phosphorylation, or the signal transduction pathway, is involved in phase- and age-related processes.