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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

Mita, S., Hirano, H., Nakamura, K.
Plant physiology 1997 v.114 no.2 pp. 575-582
Arabidopsis thaliana, anthocyanins, messenger RNA, dose response, chemical constituents of plants, glucose, sucrose, transgenic plants, starch, gene expression, cultured cells, genes, mutants, petioles, genetic variation, enzyme activity, 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 than 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 expression of AT beta-Amy in trans. The hba1 plants also had growth defects and elevated levels of anthocyanin in their petioles. However, sugar-regulated 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 of HBA1.