RESUMO
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-histidi ne 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 beta-glucuronidase reporter gene (Escherichia coli uidA) and transferred into tobacco by Agrobacterium tumefaciens-mediated leaf disc transformation. Analysis of beta-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 HRGP4.1 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.
Assuntos
Fabaceae/genética , Glicoproteínas/genética , Proteínas de Plantas/genética , Plantas Medicinais , Regiões Promotoras Genéticas , Agrobacterium tumefaciens/genética , Sequência de Aminoácidos , Sequência de Bases , Primers do DNA/genética , DNA de Plantas/genética , Escherichia coli/genética , Fabaceae/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Genes Reporter , Glucuronidase/genética , Dados de Sequência Molecular , Doenças das Plantas/genética , Plantas Tóxicas , Distribuição Tecidual , Nicotiana/genética , Vírus do Mosaico do Tabaco/genética , Transformação GenéticaRESUMO
We have characterized three different transcripts induced by fungal elicitor, wounding, or infection which encode apoproteins of cell wall hydroxyproline-rich glycoproteins involved in plant defense against infection. The proteins encoded by two of these transcripts contain a proline-rich domain involving tandem repetition of the 16-amino-acid unit Tyr3-Lys-Ser-Pro4-Ser-Pro-Ser-Pro4. The third transcript encodes a protein with a proline-rich domain involving a variant of this 16-mer canonical repeat: Tyr3-His-Ser-Pro4-Lys-His-Ser-Pro4. Each transcript is encoded by a separate gene present at single or low copy number in the haploid genome. These transcripts exhibit markedly different patterns of accumulation in different stress conditions, indicating the operation of several distinct intercellular stress signal systems in higher plants.