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1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a rate-limiting enzyme in the ethylene biosynthesis pathway. Recent studies suggest that ACS is regulated posttranslationally as well as transcriptionally. We previously reported that LeACS2, a wound-inducible ACS in tomato, is phosphorylated at Ser-460 in the C-terminal region (Tatsuki and Mori, 2001).

In the commercial fruit industry, formulations of 1-methylcyclopropene (1-MCP) are used to inhibit the action of ethylene in apple fruits destined for long-term storage. While the use of an ethylene action inhibitor impro ves firmness retention and reduces ethylene-related disorders, an unintended consequence is the failure of the fruit to ripen normally and attain characteristic fresh-quality attributes associated with taste and aroma (Blankenship and Dole, 2003). We examined reversing 1-MCP-mediated inhibition of ethylene action by using hydrogen peroxide (H2O2) to initiate normal ethylene response, and studied the effects of H2O2 on the regulation of aminocyclopropane carboxylic acid (ACC) synthase (ACS) and ACC oxidase (ACO), the two genes of ethylene biosynthesis, using polymerase chain reaction (PCR) techniques.

The phytohormone ethylene plays a central role in physiological and developmental processes, such as germination, growth, flower initiation, senescence of leaves and flowers, organ abscission, and fruit ripening (Abeles , 1992). It is also a major signal, mediating responses to a range of biotic and abiotic stresses. At the level of gene expression, ethylene has been shown to induce transcription of a wide range of genes involved in wound signalling and defense against pathogens. A family of five receptors mediates ethylene perception in Arabidopsis: ETR1, ERS1, ETR2, ERS2, and EIN4 (Hua and Meyerowitz, 1998; Sakai , 1998). The ETR1 receptor is a homodimer localized in the endoplasmic reticulum membrane (Chen , 2002).

Ethylene receptors exist as a protein family in higher plants and ethylene receptor-like proteins have been demonstrated to exist in cyanobacteria, and (Bleecker, 1999; Mount and Chang, 2002). and are thought to share a common ancestor with the cyanobacterial lineage that evolved into the modern chloroplast of higher plants. There is a possibility that ethylene receptor genes may have been transferred to higher plant genomes from a plastid genome (Huang , 2003; Stegemann , 2003.

Plants perceive a plethora of external signals and continuously adapt to changes in their environment. This phenotypic plasticity is obtained by integration of external signals as light and temperature, with internal, mainly hormonal signals that regulate development (Vandenbussche and Van Der Straeten, 2004).

It was hypothesized that methyl jasmonate (MJ) influences the binding of ethylene (C2H4) to membrane bound receptors. To address this question, C2H4 binding experiments were conducted in the presence of MJ using that transgenically expresses the ETR1 C2H4 receptor.

The quality of flowering potted plants is defined by the interaction of many factors – noticeable and hides, qualitative and quantitative – that are involved in the visual appearance and the ability to preserve the ornamental characteristics. The most important parameter of quality for the flowering potted plants is obviously the flower. The natural senescence of flower is characterized by cascade events that are genetically regulated (Jones and Woodson, 1997).

Jasmonates (JAs) including jasmonic acid (JA) and methyl jasmonate (MeJA) are a family of cyclopentanone compounds synthesised from linolenic acid via the octadecanoic pathway. In , JAs inhibit root elongation (Staswick , 1992) and are required for pollen development, anther dehiscence (Feys , 1994; McConn and Browse, 1996; Sanders ., 2000), and defence against insects (McConn , 1997), necrotrophic pathogens (Thomma , 1999) and mechanical wounding.

Abscission is a highly coordinated process in which organ detachment occurs in specific cell layers named abscission zone (Roberts 2002). Ethylene and auxins are the major hormones involved and their interaction is believed to be of paramount importance during abscission activation (Taylor and Whitelaw 2001).

Ethylene has been well established as a hormone controlling almost all aspects of vegetative development (Smalle and Van Der Straeten, 1997). The response in dark-grown pea seedlings was the first physiological effect attributed to ethylene (Neljubow, 1901).