Trehalose and trehalase in Arabidopsis

Trehalase is ubiquitous in higher plants. So far, indications concerning it s function are scarce, although it has been implicated in the detoxificatio n of exogenous trehalose. A putative trehalase gene, T19F6.15, has been ide ntified in the genome sequencing effort in Arabidopsis. Here we show that t his gene encodes a functional trehalase when its cDNA is expressed in yeast , and that it is expressed in various plant organs. Furthermore, we present results on the distribution and activity of trehalase in Arabidopsis and w e describe how inhibition of trehalase by validamycin A affects the plants response to exogenous trehalose (alpha -D-glucopyranosyl-[1, 1]-alpha -D-gl ucopyranoside). Trehalase activity was highest in floral organs, particular ly in the anthers (approximately 700 nkat g(-1) protein) and maturing siliq ues (approximately 250 nkat g(-1) protein) and much lower in leaves, stems, and roots (less than 50 nkat g(-1) protein). Inhibition of trehalase in vi vo by validamycin A led to the accumulation of an endogenous substance that had all the properties of trehalose, and to a strong reduction in sucrose and starch contents in flowers, leaves, and stems. Thus, trehalose appears to be an endogenous substance in Arabidopsis, and trehalose and trehalase m ay play a role in regulating the carbohydrate allocation in plants.