Deming Gong

Publications (2)4.72 Total impact

• Article: Regulation of 1-aminocyclopropane-1-carboxylate oxidase gene expression during leaf ontogeny in white clover

  Richard W. Scott, Sang Dong Yoo, Donald A. Hunter, Deming Gong, Balance Chen, Susanna Leung, Michael T. McManus
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  ABSTRACT: The expression of two 1-aminocyclopropane-1-carboxylate (ACC) oxidase (E.C. 1.4.3)(ACO) genes, TR-ACO2 and TR-ACO3 from white clover has been examined in leaf tissue in response to physiological stimuli. In detached mature-green leaves, the expression of TR-ACO3 (a leaf-senescence-associated ACC oxidase) is induced over a 6h time-course, while expression of TR-ACO2 (expressed constitutively in mature-green leaf tissue) decreased over the same time-course. An almost identical pattern of expression was observed with detached mature-green leaves treated with ethylene, while wounding also did not influence the timing of TR-ACO3 induction, significantly. No increase in overall ACO enzyme activity was detectable in crude extracts from wounded and detached leaf tissue, but after separation of these extracts using hydrophobic interaction column chromatography, two ACO isoforms were identified in non-wounded mature-green leaves (designated MGI and MGII), and the specific activity of one of these (MGII) increased in wounded tissues. In attached leaf tissue, TR-ACO2, but not TR-ACO3 expression was induced by treatment with ethylene; an induction that was not observed with prior treatment of plants with 1-MCP. This induction in response to ethylene was also observed at the translational level using antibodies to TR-ACO2. Analysis, in silico, of the 5′ flanking sequences to identify putative transcriptional binding domains reveals that both the TR-ACO2 and TR-ACO3 5′ flanking sequence contain domains that are associated with an ethylene-response. The significance of these observations in terms of how the expression of these ACO genes is regulated during leaf ontogeny in vivo is discussed. Keywords Trifolium repens L.-ACC oxidase-Ageing-Ethylene-Leaf development
  Plant Growth Regulation 04/2012; 62(1):31-41. · 1.60 Impact Factor
• Article: Purification and characterisation of two ACC oxidases expressed differentially during leaf ontogeny in white clover

  Deming Gong, Michael T. McManus
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  ABSTRACT: Two isoforms of ACC oxidase (ACO) (EC 1.4.3), expressed differentially during leaf ontogeny in white clover (Trifolium repens L.), have been identified and purified to homogeneity. One isoform, designated MGI, was purified from mature green leaf tissue while the second isoform, designated SEII, was purified from senescent leaf tissue. The isolation and purification of these isoforms were achieved using a combination of hydrophobic interaction chromatography, anion exchange chromatography, chromatofocusing and gel filtration column chromatography. The Mr of both MGI and SEII was determined to be 37.5 kDa by gel filtration, and 37 kDa (MGI), 35 kDa (SEII) by SDS-PAGE, indicating that both isoforms are active as monomers. During purification, both isoforms were recognised by a polyclonal antibody directed against a recombinant polypeptide derived from a white clover ACO gene expressed in mature green leaf tissue, TR-ACO2. In addition to molecular mass, differences between the two isoforms were observed in terms of pH optima, isoelectric point (pI), Km for ACC, optimal requirements for the co-substrate ascorbate, and NaHCO3 and Fe2+ as co-factors. The identification of distinct ACC oxidases from the same tissue at different developmental stages shows that the now widely observed transcriptional regulation of the ACO gene family in higher plants is also expressed in terms of differential regulation of enzyme isoforms.
  Physiologia Plantarum 12/2001; 110(1):13 - 21. · 3.11 Impact Factor