Analysis of the Poplar Phloem Proteome and Its Response to Leaf Wounding

Phloem exudate collected from hybrid poplar (Populus trichocarpa × Populus deltoides) was estimated to have more than 100 proteins, of which 48 were identified using LC-MS/MS. Comparative two-dimensional gel electrophoresis demonstrated that two phloem exudate proteins were significantly (P < 0.05) upregulated 24 h after leaf wounding. These were identified as pop3/SP1 and a thaumatin-like protein. This is the first characterization of a phloem proteome from a tree species.