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Molecular cloning and characterization of a new passion fruit allene oxide synthase (CYP74A) targeted to chloroplast.
Siqueira-Junior, C. L.1; Jardim, B. C.1; Hansen, E.1; Vicente, A. C. P.2; Otsuki, K.2; Urmenyi, T. P.3; Machado, O. L. T.4; Madureira, H. C.1; da Cunha, M.5; Oliveira, G. M. M.1 and Jacinto, T.1
1- Lab. Biotecnologia - UENF/Campos/RJ; 2- Lab de Genética Molecular de Microorganismos - Fiocruz/Rio de Janeiro/RJ; 3- Instituto de Biofíca Carlos Chagas Filho - UFRJ/Rio de Janeiro/RJ; 4- Lab. Química e Fundão de Proteínas e Peptideos UENF/Campos/RJ; 5- Lab. Biologia Celular e Tecidual UENF/Campos/RJ.
Octadecanoid metabolites (jasmonates) are involved in regulating the expression of several plant defense genes in response to biotic stress. The allene oxyde synthase (AOS) catalyzes the first step in the biosynthesis of jasmonic acid (JA). In order to study defense mechanisms against insect attack in passion fruit plants (Passiflora edulis f. flavicarpa), a cDNA encoding an AOS (PfAOS) was amplified. The full length cDNA sequence (~1,4 kb) was obtained using RT-PCR and 5'RACE approaches. The deduced aa sequence of this cDNA showed high similarity to AOS proteins from different plant species. Moreover, it contained a chloroplast targeting peptide in agreement with its role as a component of the octadecanoid pathway. Northern blot experiments using a cDNA fragment (~950 bp) as a probe showed that mechanical wounding caused an increase of PfAOS mRNA levels at local and distal leaves, as well as in response to methyl jasmonate (MJ) exposure. Furthermore, an increase in cysteine proteinase inhibitors (cystatin) in leaf tissue in response to mechanical wounding and treatment with MJ was observed. Our results suggest the importance of the octadecanoid pathway in the activation of the systemic wound response in passion fruit plants.
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