Evidence suggesting protein tyrosine phosphorylation in plants depends on the developmental conditions

Protein tyrosine phosphorylation plays a central role in a variety of signa l transduction pathways regulating animal cell growth and differentiation, but its relevance and role in plants are controversial and still largely un known. We report here that a large number of proteins from all plant subcel lular fractions are recognized by recombinant, highly specific, anti-phosph otyrosine antibodies. Protein tyrosine phosphorylation patterns vary among different adult plant tissues or somatic embryo stages and somatic embryoge nesis is blocked in vivo by a cell-permeable tyrosyl-phosphorylation inhibi tor, demonstrating the involvement of protein tyrosine phosphorylation in c ontrol of specific steps in plant development. (C) 1999 Federation of Europ ean Biochemical Societies.