A novel chitinase isozyme in tobacco BY-2 cells induced by the autoclaved Alternaria alternata culture medium

BY-2 cells form a linear linkage of several cells. Such a unique configuration is thought to be suitable for the cell-to-cell communication analysis in vivo that is the basis of the elucidation of the systemic acquired resistance in plants. Since chitinase is one of the typical stress response proteins in plants, BY-2 cells were treated with various biotic and abiotic stresses to investigate if chitinase could be induced in BY-2 cells. Among 33 stresses, the autoclaved Alternaria alternata culture medium could induce at least three chitinase isozymes. The amount of each isozyme was very small but the most abundant one, TBC-1, could be successfully isolated at the yield of 2μg from 2.4kg wet matter of BY-2 cells. The N-terminal amino acid sequence of TBC-1 was analyzed, and 24 residues were determined. The sequence was homologous to those of class IV or II chitinases of other plants, but not homologous to those of already known tobacco chitinases. Therefore, TBC-1 was a novel isozyme of tobacco chitinase and the first chitinase found in a BY-2 cell line.