Label-Free Quantitative Proteomic Analysis of Abscisic Acid Effect in Early-Stage Soybean under Flooding

Flooding
is a serious problem for soybean cultivation because it markedly reduces
growth. To investigate the role of phytohormones in soybean under
flooding stress, gel-free proteomic technique was used. When 2-day-old
soybeans were flooded, the content of abscisic acid (ABA) did not
decrease in the root, though its content decreased in untreated plant.
When ABA was added during flooding treatment, survival ratio was improved
compared with that of soybeans flooded without ABA. When 2-day-old
soybeans were flooded with ABA, the abundance of proteins related
to cell organization, vesicle transport and glycolysis decreased compared
with those in root of soybeans flooded without ABA. Furthermore, the
nuclear proteins were analyzed to identify the transcriptional regulation.
The abundance of 34 nuclear proteins such as histone deacetylase and
U2 small nuclear ribonucleoprotein increased by ABA supplementation
under flooding; however, 35 nuclear proteins such as importin alpha,
chromatin remodeling factor, zinc finger protein, transducin, and
cell division 5 protein decreased. Of them, the mRNA expression levels
of cell division cycle 5 protein, C2H2 zinc finger protein
SERRATE, CCCH type zinc finger family protein, and transducin were
significantly down-regulated under the ABA treatment. These results
suggest that ABA might be involved in the enhancement of flooding
tolerance of soybean through the control of energy conservation via
glycolytic system and the regulation on zinc finger proteins, cell
division cycle 5 protein and transducin.