Chitinase accumulates systemically in wounded poplar trees

Young leaves of poplar (Populus spp.) trees accumulate novel messenger RNAs shortly after the mature leaves have been mechanically wounded. These systemically wound-induced (win) mRNAs are thought to encode proteins involved in plant defense. In the present paper, transgenic tobacco plants that ectopically expressed a win6 cDNA contained a novel chitinase activity that was not present in normal tobacco. This demonstrated Win6 was a chitinase. Win6 and a related protein Win8 accumulated in wounded poplars. Win6 and Win8 had low isoelectric points (ca 4) as predicted from their nucleotide sequence. The wound-inducible increase in Win6 and Win8 was correlated with an increase in chitinase (EC 3.2.1.14) activity in poplar leaf extracts. We conclude that mechanical wounding induces chitinase in popular trees, and speculate that the induced chitinase activity could act to increase the tolerance of poplars to opportunistic wound pathogens.