The utilization of plant gamma-aminobutyric acid (GABA) is essential for the pathogenicity of the bacterial plant pathogen Ralstonia solanacearum. A knockout mutant in the GABA transaminase-encoding gene gabT is unable to utilize GABA as a nutrient and its ability to cause disease in plants is strongly compromised. However, the proximity of the gabD gene (encoding a succinate semialdehyde dehydrogenase) in the same operon raises the question of whether an impact on the gabD gene underlies or contributes to the virulence attenuation of the ΔgabT mutant. In this work, we use genetic complementation to show that the expression of the gabT gene is able to rescue the impaired virulence of the ΔgabT knockout mutant in tomato plants, confirming that the gabT-encoded GABA transaminase is indeed required for full virulence of R. solanacearum in a natural host plant.
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