TITLE:
Transgenic Poplar Plants for the Investigation of ABA-Dependent Salt and Drought Stress Adaptation in Trees
AUTHORS:
Domenica Hamisch, David Kaufholdt, Jennifer-Christin Kuchernig, Florian Bittner, Ralf R. Mendel, Robert Hänsch, Jennifer Popko
KEYWORDS:
ABA Biosynthesis, Drought Stress, Populus × canescens, Transgenic Poplar, Salt Stress
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.9,
July
18,
2016
ABSTRACT: Important functions of the plant hormone abscisic acid (ABA) in stress
reactions, growth and photosynthetic processes are extensively studied in the
model plant Arabidopsis thaliana.
This paper investigates the importance of Moco-sulphurase ABA3 and aldehyde
oxidase (AO) on ABA-biosynthesis in Populus × canescens. ABA3 is essential for
activation of the molybdenum enzymes AO and xanthine dehydrogenase (XDH). AO
itself catalyzes the last step in ABA-biosynthesis. Generation of transgenic
poplar plants altered in ABA3 and AO-activity using RNAi knock down and
overexpression was performed. Whereas RNAi-AO plants show a specific loss of AO
activity, the RNAi-ABA3 plants has a strongly reduced activity of both
molybdenum enzymes: AO and XDH. Constructs of AO and ABA3-promoters fused to β-glucuronidase provide the basis to
investigate transcriptional regulation of ABA-biosynthetic processes under
stress conditions. Application of high salt concentrations and different
drought stress intensities does change the endogenous AO or XDH neither on the
side of transcription nor on protein activity. On phytohormone level however,
water loss leads to increased ABA-amounts regardless of whether transgenic or
wildtype plants are studied. Salt application resulted in higher ABA-levels in
all analyzed plant lines. The down regulation of AO in the two different
RNAi-plant lines strongly prevented a wildtype-like increase of ABA-levels.
Whereas the WT plants accumulated up to 6000 ng ABA g-1 FW-1 after 16 h of salt stress exposure, plants
of the RNAi lines revealed a markedly lower increase of only up to 2000 ng ABA
g-1 FW-1. Opposing to these observations, ABA-levels
increased during drought without any influence by the RNAi-effect. These
results revealed that although stresses did not result in a visible increased
AO-activity, ABA-production was influenced by AO and ABA3 at least under salinity.