Tesis doctoral de María Josefa Rodriguez Gomez
Plant ¿-dioxygenases constitute a family of fatty acid-metabolizing enzymes that initiate the synthesis of oxylipins by catalyzing the incorporation of molecular oxygen at the ¿- methylene carbon atom of fatty acids. Previously, ¿-dox1 has been shown to display ¿- dioxygenase activity and to be implicated in plant defense. In the present ph.D. Study we investigated the function of a second ¿-dioxygenase isoform, ¿-dox2, in arabidopsis thaliana (at¿-dox2) and solanum lycopersicum (sl¿-dox2). the activity of these enzymes was studied both under in vitro conditions, through recombinant sl¿-dox2 and at¿-dox2 proteins, and in vivo conditions, establishing the presence of the lipid derivatives products of at¿-dox2 in the cases in which we observed higher expression levels of the corresponding gene. The analysis showed that recombinant sl¿-dox2 and at¿-dox2 proteins catalyzed the conversion of a wide range of fatty acids into 2(r)-hydroperoxy derivatives in vitro, and an increase in 2-hydroxy derivatives in vivo. expression of sl¿-dox2 and at¿-dox2 was found in seedlings and increased during senescence induced by detachment of leaves. The expression of at¿-dox2 during detachment is compromised in ein2-1 mutants, pointing to a role of ethylene in the control of at¿-dox2 expression. In contrast, microbial infection, earlier known to increase the expression of ¿-dox1, did not alter the expression of sl¿-dox2 or at¿-dox2. In tomato, mutation, of sl¿-dox2 also known as feebly result in severe defects in plant development and anthocyanin accumulation pointing to a critical role of the tomato ¿-dioxygenase-2 in plant development. (Van der biezen et al., 1996). A second allele named divaricata carries a mutation at the same locus, which results in a similar but milder compromised growth pointing to a critical role of the tomato ¿-dioxygenase-2 in plant development. This mutant was chosen for functional studies of ¿-dox2. Transgenic expression of at¿-dox2 and sl¿-dox2 in divaricata partially complemented the compromised phenotype in mature plants and fully complemented it in seedlings, thus indicating the functional exchangeability between ¿-dox2 from tomato and arabidopsis. However, deletion of at¿-dox2 in arabidopsis plants did not provoke any visible phenotypic alteration indicating that the relative importance of ¿-dox2 in plant physiology is species-specific.
Datos académicos de la tesis doctoral «Caracterizacion bioquimica y funcional del enzima a-dioxigenasa2«
- Título de la tesis: Caracterizacion bioquimica y funcional del enzima a-dioxigenasa2
- Autor: María Josefa Rodriguez Gomez
- Universidad: Autónoma de Madrid
- Fecha de lectura de la tesis: 13/01/2010
Dirección y tribunal
- Director de la tesis
- Carmen Castresana Fernandez
- Tribunal
- Presidente del tribunal: José Juan Sanchez serrano
- carmen Aragón rueda (vocal)
- óscar Lorenzo sánchez (vocal)
- isabel Allona alberich (vocal)