Copper excess triggers phospholipase D activity in wheat roots.
Wheat seedlings (Triticum durum Desf.) were incubated in 100muM Cu(2+) for different periods of time ranging from 1min up to 16h. Following metal addition a rapid intake of copper ions into the roots was observed. Cu(2+) induced an accumulation of both phosphatidic acid and phosphatidylbutanol within 1min of incubation, the latter indicating a very rapid induction of phospholipase D (PLD) activity. The highest PLD stimulation was detected after 2h from copper addition and decreased almost to the initial value at increasing times. Cycloheximide treatment of roots lowered phosphatidylbutanol accumulation because of a reduced PLD activity. The expression profile of a T. durum putative PLD-encoding gene showed a peak after 1h of treatment as well, indicating that enhanced gene expression contributed to the increase in PLD activity. In the absence of copper ions, roots treated with the G protein activator mastoparan showed increases in phosphatidic acid and phosphatidylbutanol similar to those detected with the metal. PLD activity was also stimulated by cholera toxin. Two putatively G protein alpha subunit encoding sequences were isolated and no significant differences in transcription activity following Cu(2+) addition were observed. In copper-treated roots an early production of superoxide generated both by total and membrane-bound NADPH oxidase occurred. The G protein inhibitor suramin as well as the PLD antagonist 1-butanol abolished copper-induced superoxide production.
Navari-Izzo
Flavia
F
Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa, Via del Borghetto 80, I-56124 Pisa, Italy. fnavari@agr.unipi.it
Cestone
Benedetta
B
Cavallini
Andrea
A
Natali
Lucia
L
Giordani
Tommaso
T
Quartacci
Mike F
MF
D003300:Copper / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D020404:Glycerophospholipids / Q000032:analysis / Q000378:metabolism; D010712:Phosphatidic Acids / Q000032:analysis / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D013997:Time Factors; D014908:Triticum / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*
D020404:Glycerophospholipids; D010712:Phosphatidic Acids; C068564:phosphatidylbutanol; D003300:Copper; D010739:Phospholipase D