Regulation and function of 1-aminocyclopropane-1-carboxylate oxidase in Petunia hybrida
Abstract
The plant hormone ethylene influences plant growth and development, from seed germination to flower senescence and the ripening of the fruit, as well as plant responses to stress, such as mechanical wounding. In petunia, an increase in ethylene synthesis is associated, in particular, with corolla senescence. Changes in gene expression, concomitant with the rise in ethylene production, allowed the isolation of a cDNA clone encoding 1-aminocyclopropane-1-carboxylate (ACC) oxidase from senescing petunia corollas. Since ACC oxidase catalyzes the conversion of ACC to ethylene, the last step in the ethylene biosynthetic pathway, the expression of ACC oxidase mRNA and protein were analyzed during development and senescence of petunia flowers. Antibodies raised against recombinant ACC oxidase in E. coli recognize a protein of the predicted molecular weight of 36 Kd, in the pistil and corolla. ACC oxidase mRNA and protein levels accumulated during development of these organs until anthesis, in the senescing corollas from pollinated and unpollinated flowers, and during maturation of the fruit. ACC oxidase transcript levels also increased rapidly after wounding of the leaves. The upregulation of ACC oxidase expression, during flower development and senescence, correlates with increased ACC oxidase activity and ethylene production. In order to further investigate the role of ethylene in plant development and flower senescence, the ACC oxidase cDNA was introduced, in the sense and antisense orientations, into petunia plants. Transgenic plants exhibited up to 65% reduction in wound-ethylene, but no alteration in flower senescence. This was probably due to insufficient suppression of the endogenous message in flower tissues. Additional phenotypes of one antisense clone include delayed germination, and reduced size of the styles and overall plant, indicating a role of ethylene during seed germination, style elongation, and vegetative growth of petunia.
Degree
Ph.D.
Advisors
Woodson, Purdue University.
Subject Area
Molecular biology|Botany
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.