Transcriptional regulation of PHACO1 in Petunia hybrida
Abstract
1-aminocyclopropane-1-carboxylate (ACC) oxidase, is the last enzyme of the ethylene biosynthetic pathway. Ethylene is involved in many aspects of plant development as well as the plant defense response. Ethylene biosynthesis was previously found to be regulated at ACC oxidase as well as ACC synthase. ACC Oxidase is encoded by three genes in Petunia hybrida , two of which were previously found to be pistil specific. The other gene, PHACO1, is expressed throughout the plant. The expression of PHACO1 was analyzed throughout petunia development and in response to wounding. Studies on the spatial regulation of PHACO1 were conducted through the analysis of transgenic petunia plants containing the PHACO1 promoter:GUS reporter gene. PHACO1 expression was induced in senescing leaves and petioles. In seedling studies, PHACO1 expression was induced in the cotyledons of dark grown seedlings as compared to the cotyledons of light grown seedlings. PHACO1 was also expressed in the hypocotyls of ethylene treated seedlings. Expression of PHACO1 was analyzed in response to wounding. PHACO1 was induced rapidly and locally in response to wounding. The wound induction of PHACO1 was independent of ethylene, although ethylene did regulate the expression of PHACO1 in an inhibitory fashion. Ethylene biosynthesis and PHACO1 expression both peaked at 60 minutes after wounding. The rapid decrease in ethylene biosynthesis and PHACO1 expression is blocked with the addition of an ethylene action inhibitor. The wound inducibility of PHACO1 in leaves of petunia is developmentally regulated. PHACO1:GUS petunia plants were analyzed for wound induction of GUS activity. Results indicated that PHACO1 is not induced in immature leaves in response to wounding. The induction of PHACO1 is more extreme as leaves age. Analysis of a PHACO1 deletion:GUS construct revealed that the induction of expression of PHACO1 in response to wounding is regulated by different promoter elements in leaves and stems. Expression of GUS in PHACO1d5:GUS petunia plants was induced by wounding in stem tissue, but was not induced by wounding in leaf tissue.
Degree
Ph.D.
Advisors
Woodson, Purdue University.
Subject Area
Molecular biology|Plant sciences
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