Our previous study has shown that copper-containing amine oxidase
( CuAO) and aminoaldehyde dehydrogenase ( AMADH)
could regulate the accumulation of γ-aminobutyric acid (GABA) in tea
plants by participating in polyamine degradation pathway. However, the
involvement of these genes in drought tolerance has not been underlined.
In this study, CsCuAO1 associated with CsAMADH1 confers
drought tolerance, which modulates GABA levels in tea plants, was
conducted. The results showed that exogenous GABA spraying effectively
alleviated the drought induced physical damage. Overexpression
Arabidopsis lines of CsCuAO1 and CsAMADH1 exhibited
enhanced resistance to drought, which promoted the synthesis of GABA and
putrescine, by alerting reactive oxygen species scavenging capacity and
stomatal movement. However, suppression of CsCuAO1 or
CsAMADH1 in tea plants exhibited increased sensitivity during
drought treatment. Moreover, the co-overexpressed plants increased the
accumulation of GABA both in the Agrobacterium-mediated
Nicotiana benthamiana transient assay and transgenic
Arabidopsis plants. In addition, a GABA transporter,
CsGAT1, was identified, whose expression is strongly correlated
with GABA accumulation levels in different tissues under drought stress.
Taken together, CsCuAO1 and CsAMADH1 were involved in
response to drought stress through a dynamic balance between GABA and
putrescine. Our data will greatly contribute to the characterization of
GABA biological functions in response to environmental stresses in
plants.