Characterization of maize endosperm-derived suspension cells throughout the culture cycle and enhancement of tissue friability

Abstract

Batch suspension cultures derived from developing maize (Zea mays L.) endosperm were examined throughout the culture cycle to determine the interaction between the tissue and the medium in relation to sugar transport and the effect of subculturing procedures on growth and friability. The growth rate and friability were improved by increasing the frequency of subculture or by physical screening during transfer. An increase in the conductivity of the medium preceded a decrease in fresh weight associated with tissue senescence. Sucrose in the medium was rapidly hydrolysed, and fructose was depleted more rapidly than glucose. Tissue sucrose concentration expressed on a dry weight basis was higher during the middle of the growth cycle, but hexose, starch, zein, lipid, and soluble protein levels changed very little. The medium pH declined from 5.2 to about 4.5 within one day of subculture. Medium pH changed to 4.5 within one day regardless of initial pH (3.0 to 7.0), indicating regulation of external pH rather than passive acidification. Results are consistent with studies of sugar uptake by these cultures, and indicate that cell clump size can be manipulated without exogenous auxin. The characterization of this tissue line establishes its suitability as a model system for studies of sugar transport and other biochemical events in developing maize endosperm.