The role of phospholipid lipids signal in rice defense reaction and seeds maturation

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1 Phospholipid metabolism in rice defense reactionHydrogen peroxide (H_2O_2)(0.01-0.1 mM) induced rapid and transient accumulation of phosphatidic acid (PA) in suspension-cultured rice cells. When phospholipase activity in the cellular extract fraction prepared from rice cells treated with H_2O_2 was assayed in the presence of 1-butanol (0.1 %), rapid and transient phosphatidylbutanol (PtdBut) formation was observed. Thus, the H_2O_2-activated phospholipase was concluded to be phospholipase D (PLD). Furthermore, H_2O_2 directly induced in vitro PLD activation in the cytosolic fraction without H_2O_2 treatment. In vitro and in vivo activation of PLD were completely suppressed in the presence of lavendustin A (0.05 mM), a potent inhibitor of protein tyrosine kinase (PTK). Phytoalexin biosynthesis induced by N-acetylchitooligosaccharide elicitor was enhanced in the presence of H_2O_2 (0.01-0.1 mM), whereas it was suppressed in the presence of tiron, a potent scavenger of O_<2^->, 1-butanol (0.1 %), and lavendustin A (0.05 mM). These results indicate that H_2O_2-inducible PLD activation enhances in signal transduction leading to phytoalexin biosynthesis in rice cells.2 Phospholipid metabolism in rice seed formation.When PLD activity in the cellular extract fraction prepared from rice seeds at 0-30 day after flowering (DAF) was assayed in the presence of 1-butanol (0.1 %), at least two kinds of PLD activities was observed. Expression pattern analysis of PLD genes by RT-PCR analysis in RNA prepared from rice seed at 0-20 DAF indicated the expressions of four kinds of PLD genes. The RNA interference vectors of the four genes were constructed into vector PZH2Bik and transformed into immature rice embryos used with Agrobacterium tumefacience strain EHA105. Then the transgenic rice plants were grown and the phenotype analysis of the plants is now underway.