Negative regulation in the expression of a sugar-inducible gene in Arabidopsis thaliana. A recessive mutation causing enhanced expression of a gene for beta-amylase.
Expression of a beta-amylase gene of Arabidopsis thaliana (AT beta-Amy) is regulated by sugars. We identified a mutant, hba1, in which the level of expression of AT beta-Amy in leaves of plants that had been grown in a medium with 2% sucrose was significantly higher than that in wild-type plants. Higher that wild-type levels of beta-amylase in hba1 plants depended on the presence of 1 to 2% sucrose or 1% glucose in the medium, whereas leaves of mutant plants grown with higher levels of sugars had beta-amylase activities similar to those in leaves of wild-type plants. The hba1 phenotype was recessive and did not affect levels of sugars and starch in leaves. It is proposed that expression of AT beta-Amy is regulated by a combination of both positive and negative factors, dependent on the level of sugars, and that HBA1 might function to maintain low-level expression of AT beta-Amy until the level of sugars reaches some high level. Results of crosses of hba1 plants with transgenic plants that harbored an AT beta-Amy:GUS transgene with 1587 bp of the 5'-upstream region suggested that HBA1 affects expressions of AT beta-Amy in trans. The hba1 plants also had growth defects and elevated levels of anthocyanin in their petioles. However, sugar-related changes in levels of several mRNAs other than beta-amylase mRNA were unaffected in hba1 plants, suggesting that only a subset of sugar-regulated genes is under the control HBA1.
Mita
S
S
Laboratory of Biochemistry, School of Agricultural Sciences, Nagoya University, Japan.
Hirano
H
H
Nakamura
K
K
D000872:Anthocyanins / Q000032:analysis; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics*; D002241:Carbohydrates / Q000032:analysis; D003433:Crosses, Genetic; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005808:Genes, Recessive; D016296:Mutagenesis; D018515:Plant Leaves / Q000187:drug effects; D030821:Plants, Genetically Modified; D013213:Starch / Q000032:analysis; D013395:Sucrose / Q000494:pharmacology*; D001614:beta-Amylase / Q000096:biosynthesis*
D000872:Anthocyanins; D002241:Carbohydrates; D003470:Culture Media; D013395:Sucrose; D013213:Starch; D001614:beta-Amylase