ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
THE SIGNALING CASCADES OF WATER LOSS TO ABSCISIC ACID ACCUMULATION IN APPLE ROOTS |
| Authors: | Y. Hong-Qiang, J. Yu-Ling, J. Wen-Suo, Z. Da-Peng |
| Keywords: | Malus hupenensis, Ca2+, H2O2, lipoxygenase, protein kinase, root, signaling, water loss, ABA |
| Abstract:
The early-response of roots to water loss and the signal transduction of water loss to abscisic acid (ABA) biosynthesis were studied by polyethylene glycol (PEG 6000) treatments to apple rootstock (Malus hupenensis Reld) seedlings. The results show that the ABA content, the H2O2 production rate, the lipoxygenase (LOX) activity and the protein kinase (PK) activity all increase during water loss (30% PEG treatment) in apple roots. H2O2 content reaches a peak at 30 ~ 40 min, then drops and rises again at 180 min following treatment. Increase of H2O2 is the earliest and of ABA content is the latest among these events. The absorbance of H2O2 and inhibition of LOX reduce the ABA accumulation during water loss. Both exogenous H2O2 and soybean LOX are able to increase ABA content. The Ca2+ chelater (EGTA) and the inhibitor of PK and LOX all reduce the increment of ABA after water loss. The activity of LOX and PK increases after treatment by 1 mmol/L H2O2 in intact roots and a PK inhibitor reduces the increase of LOX activity by PEG and H2O2. The PEG treatment-induced increases of H2O2 content, PK and LOX activity all decrease after EGTA pretreatment. It suggests that the Ca2+, protein phosphorylation, active oxygen species and LOX are all involved in the ABA biosynthesis induced by water loss; the change of cytosol Ca2+ and H2O2 is the earliest event and LOX may be a key enzyme in some conditions. The pathway of the signaling cascade associated with water loss and ABA may be: PEG treatment → loss of cell water → loss of cell turgor → mechanical process → Ca2+ → H2O2 → PK → LOX → ABA accumulation. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
