Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2004
Publication Date: 1/1/2005
Citation: Aroca, R., Amodeo, G., Fernandez-Illescas, S., Herman, E.M., Chaumont, F., Chrispells, M.J. 2005. The role of aquaporins and membrane damage in chilling and hydrogen peroxide induced changes in the hydraulic conductance of maize roots. Plant Physiology. 137:341-353.
Interpretive Summary: One of the major physiological functions of plant tissues is to mediate the movement of water from one part of the plant to another. The shifting of water distribution through the plant is a key feature of normal growth as well as in stresses, in particular drought and freezing stress. The movement of water through a plant is facilitated by specific channels in the plant cell's membranes termed aquaporins. The aquaporins are a large gene family with various members independently regulated by development and stress. In the present paper the role of aquaporins were examined in chilling stress in a cold-sensitive plant, maize. By comparing a chilling sensitive and a chilling sensitive cultivar we were able to show that the aquaporins have a necessary but not the sole role in the response to cold and avoiding injury. The results presented in this paper are primarily useful to academic investigators concerned with the response of plants to chilling injury, however, the identification of specific necessary genes may be of use to breeders as markers in the objective is to improve stress tolerance.
Technical Abstract: When chilling-sensitive plants are chilled, root hydraulic conductance (Lo) declines precipitously; Lo also declines in chilling-tolerant plants, but it subsequently recovers, whereas in chilling-sensitive plants it does not. As a result, the chilling-sensitive plants dry out and may die. Using a chilling-sensitive and a chilling-tolerant maize genotype, we investigated the effect of chilling on Lo and its relationship to osmotic water permeability of isolated root cortex protoplasts, aquaporin gene expression, aquaporin abundance and aquaporin phosphorylation, H2O2 accumulation in the roots, and electrolyte leakage from the roots. Because chilling can cause H2O2 accumulation we also determined the effects of a short H2O2 treatment of the roots and examined the same parameters. We conclude from these studies that the recovery of Lo during chilling in the chilling-tolerant genotype is made possible by avoiding or repairing membrane damage and by a greater abundance and/or activity of aquaporins. The same changes in aquaporins take place in the chilling-sensitive genotype, but we postulate that membrane damage prevents the Lo recovery. It appears that the aquaporin response is necesssary but not sufficient to respond to chilling injury. The plant must also be able to avoid the oxidative damage that accompanies chilling.