Transcriptional profiling of genes encoding GABA-transaminases in Brassica napus reveals their regulation by water deficit

Abstract

In plants, GABA (γ-aminobutyric acid) accumulates in response to a wide range of environmental stresses. The metabolism of this non-protein amino acid occurs in two distinct cellular compartments: it is synthesized in the cytosol and degraded in mitochondria. Although many studies have reported its involvement in development, the role of stress-induced GABA accumulation remains unclear. The effects of GABA accumulation have been examined in plants defective in GABA catabolism. In Arabidopsis mutants deficient for GABA transaminase (GABA-T), the first step in GABA degradation, it was shown to be involved in salt stress tolerance. Here, we investigated GABA-T genes in the Brassicaceae crop species Brassica napus at the molecular structure and transcriptional levels. We show that several copies of GABA-T are ubiquitously expressed in many organs of oilseed rape. Analysis of BnaGABA-T promoters using the GUS reporter gene found no difference in localization between GABA-T family members. Additionally, we show that their expression profiles are modified during development and in response to water stress depending on leaf rank. The role of GABA-T regulation in water stressed B. napus plants is discussed.