RESUMO
alpha-Dioxygenases are expressed in plants in response to biotic and abiotic stress. They catalyze the enantioselective 2-hydroperoxidation of long-chain fatty acids, the initial step of the alpha-oxidation pathway of fatty acids in plants. In this study, the complete cDNA of an alpha-dioxygenase from germinating pea seeds (Pisum sativum) is presented. The deduced amino acid sequence establishes that the enzyme belongs to the recently characterized family of alpha-dioxygenating enzymes in plants. We also present the first systematic study on the expression of alpha-dioxygenase in germinating and developing pea plants. During germination, alpha-dioxygenase mRNA accumulates in the cotyledons and the embryonic axis of pea seeds de novo. In developing pea plants, the transcript is detected almost exclusively in roots. The accumulation of alpha-dioxygenase protein parallels transcript accumulation in that it is abundant in germinating as well as young plant tissue, and correlates with loss of mRNA during plant maturation. alpha-Dioxygenase enzymatic activity in plant extracts is highest in cotyledons during imbibition. In the embryonic axis and roots of developing plants comparable activity levels are observed, whereas in shoots little alpha-oxidation activity is detected. With this contribution, we present information on the temporal and spatial expression of alpha-dioxygenase during plant germination and development, supporting the hypothesis that the alpha-oxidation pathway of fatty acids plays a role during plant developmental processes.
