Membrane stabilization by abscisic acid under cold aids proline in alleviating chilling injury in maize (Zea mays L.) cultured cells

Abstract

Previous studies of maize suspension-cultured cells showed that abscisic acid (ABA) treatment at warm temperatures improved the tolerance of cells to subsequent chilling. In the present study, it is shown that both ABA-treated and untreated maize cells accumulated proline in response to chilling. However, ABA-treated cells displayed less lipid peroxidatian during chilling, and thus, unlike untreated cells, were able to retain the accumulated proline intracellularly. Proline application experiments indicate that an intracellular proline level higher than 2 μmole (g FW)-1 prior to chilling was needed to meaningfully reduce chilling-enhanced lipid peroxidation and significantly improve chilling tolerance. The results suggest that total proline accumulation in ABA-treated as well as untreated cells during chilling was enough to potentially improve chilling tolerance, but proline leakage rendered the control cells unable to benefit from the endogenous synthesis of proline in relation to the alleviation of chilling injury. Proline participated in chilling tolerance improvement in ABA-treated maize cells, as evidenced by: (1) the inhibition of proline accumulation by L-methionine-D, L-sulphoximine (MSO), an inhibitor of glutamine synthetase, reduced ABA-improved chilling tolerance, and (2) the addition of glutamine into the medium prevented the MSO-induced reduction in chilling tolerance. The revised relationship between proline accumulation and membrane stability at cold is discussed in the light of these current findings.