Stress activation of a bean hydroxyproline-rich glycoprotein promoter is superimposed on a pattern of tissue-specific developmental expression

Abstract

The HRGP4.1 gene, which encodes a cell wall hydroxyproline-rich glycoprotein, was isolated from a genomic library of bean (Phaseolus vulgaris L.). Two transcripts, one induced by wounding and one by elicitation, were transcribed from the same initiation site. The gene encodes a polypeptide of 580 amino acids with the amino terminal half consisting of repeats of the sequence serine-(proline)4-lysine-histidine-serine-(proline) 4-(tyrosine)3-histidine and the carboxyl-terminal half composed of repeats of the sequence serine-(proline)4-valine-tyrosine-lysine-tyrosine-lysine. A 964-bp upstream promoter fragment was translationally fused to the β-glucuronidase reporter gene (Escherichia coli uidA) and transferred into tobacco by Agrobacterium tumefaciens-mediated leaf disc transformation. Analysis of β-glucuronidase activity showed that wounding caused local activation of the HRGP4.1 promoter in the phloem. Infection by tobacco mosaic virus was a less effective inducer than wounding. Stress induction was superimposed on tissue-specific developmental expression in stem nodes and root tips, suggesting that HRCP4.1 may have specific structural roles in development as well as protective functions in defense. Deletion analysis showed that control of tissue specificity and wound inducibility lies in a region between -94 and -251 relative to the transcription start site and that activation by infection lies outside that region.