Cloning and expression analysis of a cDNA partially encoding glutamate dehydrogenase in lettuce during storage
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J. Crop Sci. Biotech. 2009 (June) 12 (2) : 73 ~ 78 DOI No. 10.1007/s12892-009-0084-x RESEARCH ARTICLE
Cloning and Expression Analysis of a cDNA Partially Encoding Glutamate Dehydrogenase in Lettuce during Storage Dulal Chandra1*, Toshiyuki Matsui1, Haruo Suzuki1, Yusuke Kosugi1, and Koichi Fujimura2 Department of Bioresource Production Science, Faculty of Agriculture, Kagawa University, Miki-cho, Ikenobe 2393, Kagawa 761-0795, Japan 2 Kagawa Prefectural Agricultural Experiment Station, Busshouzan, Takamatsu, Kagawa 761-8078, Japan
1
Received: April 24, 2009 / Accepted: May 18, 2009 Ⓒ Korean Society of Crop Science and Springer 2009
Abstract The changes in ammonia content as well as activity and gene expression of glutamate dehydrogenase (GDH; EC 1.4.1.2) were investigated in lettuce during storage. GDH amination activity increased with the increases in ammonia content in the outer leaf portion after 24 h of storage. GDH amination activity was substantially higher than deamination activity. The isolated partial cDNA clone referred to as LsGDH (Lactuca sativa glutamate dehydrogenase; AB334207) consisted of 757 nucleotides and was highly homologous with the GDH genes of other plants. Although the transcript of LsGDH was found in both the outer and inner leaves, the level of transcript gradually increased in the outer leaves with the progress of storage, but was only expressed in the inner leaves when higher enzyme activity was observed. Results suggest that GDH expression in lettuce is controlled by tissue specific manner and/or multiple levels of regulations. Key words: Ammonium, cDNA, gene expression, glutamate dehydrogenase, Lactuca sativa
Introduction Leafy vegetables are at their best quality at the moment of harvest. Due to high water content, they are prone to high water loss which makes them highly perishable. Freshness of vegetables such as lettuce can be maintained by immediate cooling after harvest followed by maintenance of low temperature throughout the entire postharvest transport and retail marketing procedures. However, maintaining such conditions from harvest to consumption is sometimes unmanageable due to lack of facilities. In lettuce, although deterioration starts with the harvest through the loss of moisture and stored energy, storage at ambient temperature results in the changes of many physio-biochemical processes. Additionally, they are subjected to metabolic changes as well as mechanical, pathological, and physiological disorders. These metabolic changes in leafy green vegetables are characterized by the proteolysis of high molecular protein into Dulal Chandra ( ) E-mail: [email protected] Tel: +81-87-891-3076
The Korean Society of Crop Science
low molecular compounds resulting in the accumulation of amino acids and free ammonia (Schwerdtfeger 1978). However, accumulation of ammonium may cause harmful effects in the plant cells (Hurst and Clark 1993), hence, its rapid assimilation is necessary to prevent or minimize the harmful effects which ultimately enhance quality deterioration.
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