Mutants of Arabidopsis thaliana with pleiotropic effects on the expression of the gene for β‐amylase and on the accumulation of anthocyanin that are inducible by sugars

We identified a mutant of Arabidopsis thaliana ecotype Col-0 in which significantly reduced levels of expression of the gene for β-amylase (ATβ-Amy) were detected in leaves in response to high concentrations of sucrose, glucose or fructose. Genetic studies, including a cross with transgenic plants that harbored the ATβ-Amy:GUS transgene with the promoter of ATβ-Amy, indicated that this phenotype was caused by a recessive mutation, Iba1, that affected expression of ATβ-Amy in trans. We also found a reduced level of sugar-induced expression of ATβ-Amy in the Landsberg erecta (Ler) ecotype compared with other ecotypes. This phenotype seemed to be due to a recessive trait, provisionally designated Iba2, that was linked to neither erecta nor Iba1. The Iba2 mutation also affected expression of ATβ-Amy:GUS transgene. Accumulation of starch and sugars after treatment of leaves with sucrose was not affected in the Iba1 mutant and Ler plants. However, both Iba1 mutant and Ler plants accumulated low levels of anthocyanin in response to sucrose, results that suggested the existence of some genetic linkage between regulation of the expression of ATβ-Amy and regulation of the accumulation of anthocyanin. Although the Iba1 and Iba2 mutations did not affect sugar-inducible gene expression in general, the expression of sugar-regulated genes other than the gene for β-amylase was differentially affected in the Iba1 mutant and Ler plants. These results suggest that the sugar-regulated expression of many genes in plants might be mediated by multiple signal-transduction pathways.