The transcript levels of the phytoglobin (Pgb) genes Pgb1 and Pgb3, and the protein content of Pgb1 were responsive to anaerobiosis in several tissues of barley (Hordeum vulgare L.). Oxygen deficiency induced the level of both Pgb transcripts and protein in aleurone layers and coleoptiles, as well as up-regulated both Pgb1 and Pgb3 in leaves, apexes and more strongly in roots of barley seedlings. In O2-depleted aleurone cells the induction of the Pgb transcript-protein pair was reversed by re-supplying O2. Based on this observation, it is suggested that Pgb1 and Pgb3 are inducible in all tissues. In aleurone cells, gibberellic acid (GA) induced Pgb1 and Pgb3 together with α-amylase, whereas abscisic acid (ABA) eliminated the GA stimulating effects on both α-amylase and Pgb1 and Pgb3 expression. While GA had no effects on alcohol dehydrogenase (Adh1, Adh2 and Adh3) transcripts, ABA induced all three Adh genes. It is concluded that Pgb and α-amylase in seeds are regulated reciprocally with the ethanolic fermentation pathway, and that Pgb induction is mediated by GA. Nitric oxide turnover and scavenging mediated by Pgb represents an important alternative to fermentation under anoxia.
Keywords: Abscisic acid; Alcohol dehydrogenase; Anoxia; Barley (Hordeum vulgare L.); Gibberellic acid; Phytoglobin.
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