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The Existence of Phospholipase A(2) Activity in Plant Mitochondria and Its Activation by Hyperosmotic Stress in Durum Wheat (Triticum Durum Desf.)

The Existence of Phospholipase A(2) Activity in Plant Mitochondria and Its Activation by Hyperosmotic Stress in Durum Wheat (Triticum Durum Desf.)

Daniela Trono, Mario Soccio, Maura N Laus, Donato Pastore

Plant Sci. 2013 Feb;199-200:91-102.

PMID: 23265322

Abstract:

The activity of mitochondrial phospholipase A(2) (PLA(2)) was shown for the first time in plants. It was observed in etiolated seedlings from durum wheat, barley, tomato, spelt and green seedlings of maize, but not in potato and topinambur tubers and lentil etiolated seedlings. This result was achieved by a novel spectrophotometric assay based on the coupled PLA(2)/lipoxygenase reactions using 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine as substrate; the mitochondrial localisation was assessed by checking recovery of marker enzymes. Durum wheat mitochondrial PLA(2) (DWM-PLA(2)) showed maximal activity at pH 9.0 and 1mM Ca(2+), hyperbolic kinetics (K(m)=90±6μM, V(max)=29±1nmolmin(-1)mg(-1) of protein) and inhibition by methyl arachidonyl fluorophosphonate, 5-(4-benzyloxyphenyl)-4S-(7-phenylheptanoylamino)pentanoic acid and palmityl trifluoromethyl ketone. Reactive oxygen species had no effect on DWM-PLA(2), that instead was activated by about 50% and 95%, respectively, under salt (0.21M NaCl) and osmotic (0.42M mannitol) stress imposed during germination. Contrarily, a secondary Ca(2+)-independent activity, having optimum at pH 7.0, was stress-insensitive. We propose that the activation of DWM-PLA(2) is responsible for the strong increase of free fatty acids recently measured in mitochondria under the same stress conditions [Laus, et al., J. Exp. Bot. 62 (2011) 141-154] that, in turn, activate potassium channel and uncoupling protein, able to counteract hyperosmotic stress.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP141022993-B	Palmityl trifluoromethyl ketone		141022-99-3	Price

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