Osmotically-stressed poplar cell cultures: anthocyanin accumulation, deaminase activity, and solute composition

Abstract

Anthocyanin accumulated in mannitol-stressed cell suspensions of poplar [Populus deltoides (Marsh) Bartr, var. occidentalis (Rydb.)] in culture. Both phenylalanine ammonia lyase (PAL, EC 4.3.1.5) and tyrosine ammonia lyase (TAL, EC 4.3.1) activities increased in the stressed cells, but PAL activity was up to 9 times higher than that of TAL. Two separate enzymes were found, and the increased PAL activity of the osmotically-stressed cells was correlated with increased levels of PAL protein. Greater contents of organic solutes accumulated in the stressed cells compared to control cells. Of the amino acids, higher contents of alanine, glutamine, glutamate, asparagine, and serine were present in the stressed cells. Although the organic acid content of the cells declined in culture, stressed cells contained higher concentrations. The soluble carbohydrate content of the stressed cells was higher, not only due to the uptake of mannitol, but also due to sucrose, and inositol to a lesser extent. All of these organic compounds could act colligatively in osmotic-stress adjustment, and some of them could influence the activity of the deaminating enzymes.