Defense responses elicited in pine cell suspension cultures

To understand mechanisms of disease resistance in pine trees, we took advantage of the fact that suspension cultured cells exhibit many of the defense responses that are characteristic of intact tissues. In this study, we measured constitutive and elicitor-induced levels of ethylene production, chitinase activity and glucanase activity in cells of loblolly pine (Pinus taeda L). Increased ethylene production was induced similarly by a Live fungus (Ophiostoma minus Hedge. H.P. Sydow) and chitosan, a general elicitor. Culture age, relative to the most recent transfer, affected the constitutive level of all defense responses. Culture age also had a pronounced effect on the ability of the cells to produce ethylene and cellular chitinase, but not on secreted chitinase, cellular glucanase, secreted glucanase, or lignification. In older cultures, elicitation induced a 4- to 10-fold increase in ethylene production and a 2-fold increase in cellular chitinase, secreted chitinase and cellular glucanase. Chitosan elicitation did not affect secreted glucanase. The overall regulation of the defense response in pine cells appears complex, but individual components of the response can be differentially induced in cell cultures under appropriate experimental conditions.