Expression of a P450 gene in barley (Hordeum vulgare)

A new member of the P450 gene family was identified in barley. The P450 gene was a member of the subfamily CYP72A. Northern analysis revealed that various CYP72A39 transcripts were found in four barley cultivars at a very early vegetative stage but no expression was detected at the reproduction stage. This suggested that this P450 gene may be involved in seedling development in barley. Comparison of expression profiles of this gene and “digital expression” databases confirmed that this gene was homologous to several cereal EST clones with tissue-specific transcripts responding to various environmental stimuli. Among these, many transcripts in barley were obtained from stressed tissues at the vegetative stage, and two transcripts in wheat were expressed after being challenged by barley powdery mildew pathogen (Bumeria graminis f. sp. hordei). This suggested that the CYP72A39 gene may play a role in defence in the barley seedling. Introduction Plant P450s belong to the cytochrome group of membrane-bound enzymes, that are usually found in plant endoplasmic reticulum (Halkier, 1996). Among 6008 P450 genes reported in all organisms including human, one third of them have been reported in plant species. In plants, P450s play a central role in numerous biosynthetic pathways such as production of second metabolites (phenylpropanoids, alkaloids, lipids, sterols, flavonoids and cyanogenic glycosides). In addition, plant P450s have a significant response to stresses (Whitbred and Schuler, 2000) and disease (Smigocki and Wilson, 2004; Takemoto et al., 1999). P450 enzymes that are encoded by P450 genes are important components of the defense mechanism of plants through their enzymatic reactions in various biosynthesis pathways. Depending on the type of stimuli, specific enzymes are produced under stress conditions. Many reports (Bolwell et al., 1994; Halkier, 1996; Mizutani et al., 1998; Persans et al., 2001; Schuler and Wreck-Reichhart, 2003; Toguri et al., 1993c) have emphasized the affects of environmental factors such as stresses (salinity, low temperature, pathogen elicitation) as well as developmental factors (plant age, tissue specific) on the expression pattern of plant P450. Here we report the identification and analysis of expression patterns of a new P450 gene in barley. Materials and methods Randomly selected clones (512) from a cDNA library of four day old seedling (cv Alexis) were sequenced. Details of the cDNA library construction were previously described by Holton and co-workers (2002). A clone (5E2) was identified showing 72% homology to a P450 (CYP72A21) in rice.