PR proteins are important components of active defences induced by pathogens in plants. This activation occurs through different transduction pathways requiring signal molecules such as salicylic acid (SA), jasmonate (JA) or ethylene, as demonstrated by studies on mutants and by observations that exogenous treatments with these chemicals induce distinct resistance responses in plants. Different signalling pathways leading to increased transcription of diverse PR genes interact in complex ways, which have been mainly studied in dicot species. However, the emerging picture suggests that regulation mechanisms of active defences in monocots are at least in part divergent from the more characterised pathways in dicots. To contribute to the understanding of defence genes regulation in monocots, we characterised wPR4e, a genomic wheat clone encoding a PR4 protein, in terms of transcriptional activity of its 5' region. The putative 1700 bp promoter region of wPR4e, XS, containing several cis-acting domains found in other defence genes, was cloned upstream of the GUS reporter gene in pUC8 and pKYLX71 plasmids. The recombinant plasmids pUCXS::GUS and pKYXS::GUS were then used for biolistic- and A. tumefaciens-mediated transformation of tobacco, respectively. Transient and stable transformants were subjected to different treatments to determine which signals are involved in the regulation of the wPR4e gene. Upon bombardment with pUCXS::GUS, tobacco leaves were submerged in 1 mM SA for 1 min and checked for GUS expression after 12, 24 and 48h. GUS expression assays demonstrated that the 1700 bp 5' sequence of wPR4e is able to drive transient GUS expression and that this expression increases upon SA-treatment. Several independent XS::GUS stable transformants were obtained by A. tumefaciens transformation which were tested for GUS expression upon leaf treatments with SA (100 uM) or JA (100 uM) for 12, 24 and 48h or 12, 24 and 48h after wounding. GUS assays confirmed that the wPR4e promoter is able to drive constitutive expression of the reporter gene and that GUS transcription increases upon SA treatment. Besides, a very strong induction of GUS expression was observed upon treatment with JA, while wounding activated transcription of the reporter gene at levels comparable to SA. These results confirm that activation of at least one wheat PR4 gene follows both SA- and JA-dependent pathways, while Arabidopsis PR4 genes are induced through JA signaling.
A wheat Pathogenesis-Related promoter is responsive to salicylic acid, methyl jasmonate and wounding
De Palma M;Tucci M
2004
Abstract
PR proteins are important components of active defences induced by pathogens in plants. This activation occurs through different transduction pathways requiring signal molecules such as salicylic acid (SA), jasmonate (JA) or ethylene, as demonstrated by studies on mutants and by observations that exogenous treatments with these chemicals induce distinct resistance responses in plants. Different signalling pathways leading to increased transcription of diverse PR genes interact in complex ways, which have been mainly studied in dicot species. However, the emerging picture suggests that regulation mechanisms of active defences in monocots are at least in part divergent from the more characterised pathways in dicots. To contribute to the understanding of defence genes regulation in monocots, we characterised wPR4e, a genomic wheat clone encoding a PR4 protein, in terms of transcriptional activity of its 5' region. The putative 1700 bp promoter region of wPR4e, XS, containing several cis-acting domains found in other defence genes, was cloned upstream of the GUS reporter gene in pUC8 and pKYLX71 plasmids. The recombinant plasmids pUCXS::GUS and pKYXS::GUS were then used for biolistic- and A. tumefaciens-mediated transformation of tobacco, respectively. Transient and stable transformants were subjected to different treatments to determine which signals are involved in the regulation of the wPR4e gene. Upon bombardment with pUCXS::GUS, tobacco leaves were submerged in 1 mM SA for 1 min and checked for GUS expression after 12, 24 and 48h. GUS expression assays demonstrated that the 1700 bp 5' sequence of wPR4e is able to drive transient GUS expression and that this expression increases upon SA-treatment. Several independent XS::GUS stable transformants were obtained by A. tumefaciens transformation which were tested for GUS expression upon leaf treatments with SA (100 uM) or JA (100 uM) for 12, 24 and 48h or 12, 24 and 48h after wounding. GUS assays confirmed that the wPR4e promoter is able to drive constitutive expression of the reporter gene and that GUS transcription increases upon SA treatment. Besides, a very strong induction of GUS expression was observed upon treatment with JA, while wounding activated transcription of the reporter gene at levels comparable to SA. These results confirm that activation of at least one wheat PR4 gene follows both SA- and JA-dependent pathways, while Arabidopsis PR4 genes are induced through JA signaling.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
