The Hydrogen Sulfide Donor NaHS Delays Programmed Cell Death in Barley Aleurone Layers by Acting as an Antioxidant

H2S is a signaling molecule in plants and animals. Here we investigated the effects of H2S on programmed cell death (PCD) in barley (Hordeum vulgareL.) aleurone layers. The H2S donor NaHS significantly delayed PCD in aleurone layers isolated from imbibed embryoless barley grain. NaHS at 0.25 mM effectively reduced the accumulation of superoxide anion (·O2-), hydrogen peroxide (H2O2), and malondialdehyde (MDA), promoted the activity of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and decreased those of lipoxygenase (LOX) in isolated aleurone layers. Quantitative-PCR showed that NaHS treatment of aleurone tissue led to enhanced transcript levels of the antioxidant genesHvSOD1, HvAPX, HvCAT1, andHvCAT2and repressed transcript levels ofHvLOX(lipoxygenase gene) and of two cysteine protease genesHvEPAandHvCP3-31. NaHS treatment in gibberellic acid- (GA-) treated aleurone layers also delayed the PCD process, reduced the content of·O2-, and increased POD activity while decreasing LOX activity. Furthermore,α-amylase secretion in barley aleurone layers was enhanced by NaHS treatment regardless of the presence or absence of GA. These data imply that H2S acted as an antioxidant in delaying PCD and enhancesα-amylase secretion regardless of the presence of GA in barley aleurone layers.

Inositol phosphates in barley (Hordeum vulgare L.) aleurone tissue are stereochemically similar to the products of breakdown of InsP6in vitro by wheat-bran phytase

Partisphere SAX HPLC analysis of endogenous inositol phosphates in [3H]inositol-labelled barley aleurone tissue revealed a range of isomers, including d- and/or l-Ins3P, d- and/or l-Ins(1,4)P2, d- and/or l-Ins(1,2)P2, a third unidentified InsP2, Ins(1,2,3)P3, d- and/or l-Ins(1,2,6)P3, d-and/or l-Ins(1,2,3,4)P4, d- and/or l-Ins(1,2,5,6)P4, Ins(1,3,4,5,6)P5, d- and/or l-Ins(1,2,3,4,5)P5, Ins(1,2,3,4,6)P5, InsP6 and a molecule with the chromatographic properties of an inositol pyrophosphate. The striking match between the identities of the stereoisomers, and in some cases enantiomers, detected in vivo and those stereoisomers produced in vitro by the action of wheat-bran phytase on InsP6 [Cosgrove (1980) Inositol Phosphates: Their Chemistry, Biochemistry and Physiology, Elsevier, Amsterdam] strongly suggests that most of the inositol phosphates identified are products of the breakdown of InsP6 by endogenous phytase(s) with stereospecificity similar to that of the wheat-bran enzyme(s).