Sugar-Inducible Expression of a Gene for [beta]-Amylase in Arabidopsis thaliana

Abstract

The levels of [beta]-amylase activity and of the mRNA for [beta]-amylase in rosette leaves of Arabidopsis thaliana (L.) Heynh. increased significantly, with the concomitant accumulation of starch, when whole plants or excised mature leaves were supplied with sucrose. A supply of glucose or fructose, but not of mannitol or sorbitol, to plants also induced the expression of the gene for [beta]-amylase, and the induction occurred not only in rosette leaves but also in roots, stems, and bracts. These results suggest that the gene for [beta]-amylase of Arabidopsis is subject to regulation by a carbohydrate metabolic signal, and expression of the gene in various tissues may be regulated by the carbon partitioning and sink-source interactions in the whole plant. The sugar-inducible expression of the gene in Arabidopsis was severely repressed in the absence of light. The sugar-inducible expression in the light was not inhibited by 3(3,4-dichlorophenyl)-1,1-dimethylurea or by chloramphenicol, but it was inhibited by cycloheximide. These results suggest that a light-induced signal and de novo synthesis of proteins in the cytoplasm are involved in the regulation. A fusion gene composed of the 5[prime] up-stream region of the gene for [beta]-amylase from Arabidopsis and the coding sequence of [beta]-glucuronidase showed the sugar-inducible expression in a light-dependent manner in rosette leaves of transgenic Arabidopsis.