Structure and expression of 1-aminocyclopropane-1-carboxylate oxidase gene family in Petunia hybrida
Abstract
1-Aminocyclopropane-1-carboxylate (ACC) oxidase, the last enzyme in the ethylene biosynthetic pathway, is involved in regulation of ethylene production. Four ACC oxidase genes, ACO1, ACO2, ACO3, and ACO4, have been cloned from Petunia hybrida. Restriction endonuclease mapping and sequence analysis reveals that they are tandemly arranged in two clusters with ACO1 and ACO2 in one cluster and ACO3 and ACO4 in another cluster. Each gene has four exons interrupted by three introns. The exons are highly conserved among the genes, but the 5$\sp\prime$ flanking regions, the introns and the 3$\sp\prime$ untranslated-regions are divergent. mRNA-based reverse transcriptional PCR and cDNA cloning have shown that ACO1, ACO3 and ACO4 are actively transcribed. RNA gel blot analysis with gene-specific probes reveals that the ACO1 is expressed in senescing corollas and in all the floral organs including sepals, petals, stamens, stigma/styles and ovaries following exposure to ethylene. The ACO3 and ACO4 genes are specifically expressed in pistils during flower development and are also induced by ethylene. In situ hybridization experiments reveal that the developmentally regulated ACC oxidase mRNAs are specifically localized to the secretory cells of the stigma, the epidermis cells of placenta, and the connective tissue of the receptacle, including nactories. Treatment of flower buds with ethylene results in the distribution of ACC oxidase mRNA distinct from the pattern seen during flower development with abundant transcripts detected in transmitting tract and ovule cells. Expression of ACC oxidase RNA in stigma during flower development is paralleled by the physiological processes associated with reproduction. The abundance of ACC oxidase mRNA in stigma correlates with the rate of ethylene production following pollination. Although ACC oxidase RNA in stigma/styles of young bud is barely detectable, it is greatly induced by an ethylene-independent signal released during pollination. The increase of ACC oxidase RNA parallels the rate of ethylene production by the young stigma/style following pollination. These results suggest that ACC oxidase is involved in regulation of ethylene production following pollination.
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.