|Hincha, Dirk - MAX-PLANCK INSTUTUTE|
|Heyer, Arnd - STUTTGART UNIVERSITY|
Submitted to: Cellular and Molecular Life Sciences
Publication Type: Review Article
Publication Acceptance Date: December 12, 2008
Publication Date: February 19, 2009
Citation: Livingston, D.P., Hincha, D.K., Heyer, A.G. 2009. The relationship of fructan to abiotic stress tolerance in plants. Cellular and Molecular Life Sciences. 66:2007-2023. Interpretive Summary: Fructan is a plant carbohydrate similar to starch that is composed of fructose molecules hooked together in a chain. It has been studies in various capacities for at least 200 years. Some of its' unique properties have made it a candidate for research investigating mechanisms of resistance to freezing, drought and salt stress. The purpose of this article is to bring the reader up to date with regard to some of the newer findings in fructan research and how these findings impact our knowledge of freezing and drought stress. While one proposed mechanism of fructan being involved in lowering the freezing point to water in plants has never been proven false, recent research has indicated that fructan has the capacity to protect membranes by becoming embedded within the matrix of the membrane which strengthens it against rupture. In addition, plants that normally do not accumulate fructan were induced to do so by transferring genes from plants that do accumulate fructan. The drought and freezing tolerance of these transformed plants increased as a result of their new ability to accumulate fructan. These studies all support the importance of fructan in helping plants resist abiotic stress.
Technical Abstract: Fructan is a crucial component of drought and freeze protection in plants. Numerous studies have published that attempted to correlate fructan concentrations with freezing and drought tolerance. As model membrane systems became available, investigations to study the effect of fructan on liposomes were initiated. These studies indicated that a direct interaction between membranes and fructan was possible. This new area of research began to move fructan and its' association with stress beyond mere correlation by confirming that fructan has the capacity to stabilize membranes during drying by inserting at least part of the polysaccharide into the lipid headgroup of the membrane. This helps prevent leakage when water is removed from the system either during freezing or drought. In addition to evidence from studies with model membranes, when plants were transformed with the ability to synthesize fructan, a concomitant increase in drought and or freezing tolerance was confirmed. While exact mechanisms are still open for consideration it has become clear that besides an indirect effect of supplying tissues with hexose sugars when the need arises, fructan has a direct protective effect that can be demonstrated by both model systems and genetic transformation. These studies will help breeders as they attempt to combine favorable genes into agronomically acceptable cultivars and extend their cultivation into regions where they currently cannot be grown.