GENETIC AND MOLECULAR CHARACTERIZATION OF MUTANTS ARABIDOPSIS THALIANA ALTERED GENE EXPRESSION DEFENSEAuthor:
MARQUÉS ROMERO MARÍA CARMEN.
Year:
2004.
University:
POLITÉCNICA DE VALENCIA [
www.upv.es].
Place of defense: Dep. Biotecnologia.
Place of preparation: Universidad Politécnica de Valencia.
Summary: In the present work we have characterized several mutant of Arabidopsis thaliana presenting defects in the expression of genes related to the defense. The mutants obi (overexpressor of basic PR1 isoform) constitutively expressing the transgene PR1b1:: GUS, formed by the merger of transcriptional promoter gene PR1b1 (which encodes for a isoform basic family PR1 tomato) with the coding region of the gene marker GUS. A detailed study of mutant recessive obi1 shows that it presents a greater accumulation of ethylene (ET) after infection with the bacteria Pseudomonas syringae but defects in the activation of genes dependent acid jasmónico (BOA) and ET despite not having abnormal the perception of the two signals. This mutant also shows greater activation responses dependent salicylic acid (SA) and greater accumulation of SA, but this does not translate into a difference in the levels of resistance to different pathogens. The analysis of the double mutants obtained between obi1 and other defense-related mutants, as is the case with npr1, cpr1, etr1 or transgenic line NahG, reveals a requirement of SA for the constitutive expression of PR1b1:: GUS. Additionally, we found that the mutation obi1 proves to be dominant in nature to control the responses dependent on SA and recessive for the regulation of the ET-dependent, which would suggest a possible involvement of OBI1 in amplification of the signal SA for the establishment of SAR. We note that in this study the activation of transgene PR1b1:: GUS requires joint action by the signals SA and ET and is associated with symptoms cloróticos occurring at the site of infection. The exogenous application of the two signals produced in wild plants not only accelerated senescence, but also an increased susceptibility to pathogens. All this points to the involvement of OR gene
