Activation of the gene promoter of barley beta-1,3-glucanase isoenzyme GIII is salicylic acid (SA)-dependent in transgenic rice plants

Abstract

Pathogenesis-related proteins (PR), including beta-1,3-glucanases may provide the first line of defense against fungal pathogens. Many PR proteins are activated by salicylic acid (SA), which acts as an endogenous signal. We have previously isolated seven members of the beta-1,3-glucanase gene family in barley (Hordeum vulgare). In this paper, we characterized the beta-1,3-glucanase isoenzyme GIII for SA-responsive elements in the GIII gene promoter. A series of deletion mutations of the promoter were fused to the reporter gene beta-glucuronidase (gus). The GUS activity was analyzed in rice calli (Oryza sativa L.) in response to SA. A deletion fragment between -362 and +106 bp showed the highest level of GUS activity in these assays. This promoter fused with gus was further introduced into rice plants for stable transformation. Histochemical staining and fluorometric quantitation of GUS activity in leaves of transgenic plants revealed prominent GUS expression after SA induction. RNA analysis by Northern blotting confirmed the importance of this region, indicating that cis-acting elements required for SA-inducible expression exist within 362 bp upstream from the transcriptional start site.