Biological responses of suspension cultures of Taxus chinensis var. mairei to shear stresses in the short term.

The biological responses of Taxus chinensis var. mairei suspension cultures to a range of shear rates were investigated in a Couette-type shear reactor. It was found that the shear rate below 458 s-1 enhanced the primary metabolism, increasing mitochondrial activity and protein expression and inhibiting the activity of phenylalanine ammonia lyase (PAL), an enzyme relevant to the secondary metabolism. However, the shear rate over 719 s-1 damaged taxus cells to some extent, decreasing the mitochondrial activity, increasing the membrane permeability, and even causing cell hypersensitive responses. As a result, PAL and intracellular peroxidase, an enzyme in cells relevant to reactive oxygen species scavenging, were activated and extracellular phenolics were accumulated. Additionally, shear-induced accumulation of free radicals and alkalization of the culture medium were observed. The results might shed light on a better understanding of the mechanism of plant cells responses to shear stress through the signal transduction pathway.