Enhanced Desiccation Survival by Engineering Osmolyte Biosynthesis in Plants

ET PALVA; KO HOLMSTRÖM; E MÄNTYLÄ; B WELIN

Physical stresses in plants

Springer

Lugar: Berlin; Año: 1996; p. 187 - 198

Plant growth, productivity and distribution are severely limited by environmental stress factors such as drought, salinity and freezing temperatures, all of which disturb the water balance of the cell. Plants as well as other organisms have evolved different strategies to alleviate the adverse effects of these stresses. A common adaptive response to stresses that results in water deficit is the accumulation of osmolytes or osmoprotectants that help cells to maintain their water balance and, in addition, protect macromolecules in stressed cells. The simplicity of the metabolic pathways leading to osmolyte biosynthesis makes them amenable to genetic engineering. We will discuss engineering the biosynthetic pathways of two different types of osmoprotectants, the quaternary ammonium compound glycine betaine, and the nonreducing disaccharide trehalose. Biosynthesis of both compounds is a two-step process in prokaryotes as well as in eukaryotes. For biosynthesis of glycine betaine we employed the bacterial genes betA and betB encoding choline dehydrogenase and betaine aldehyde dehydrogenase, respectively. These genes have been expressed in transgenic tobacco and were shown to result in biosynthesis of glycine betaine. For biosynthesis of trehalose we used the TPS1 gene from yeast encoding the first enzyme of the pathway, trehalose-6-phosphate synthase. Transgenic tobacco plants expressing TPS1 were shown to produce active TPS1 and accumulate trehalose in the leaves. Production of trehalose was associated with enhanced desiccation survival both in primary transformants and TPS1- positive progeny. The results suggest that engineering osmolyte biosynthesis may provide an efficient strategy to generate crop plants with enhanced tolerance to water deficit as well as improved post harvest storage properties.