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Articles by Dulal Chandra
Total Records ( 2 ) for Dulal Chandra
  Dulal Chandra , Toshiyuki Matsui , Haruo Suzuki , Yusuke Kosugi and Koichi Fujimura
  In order to understand the factors contributing to postharvest deterioration of lettuce, the changes in ammonia content as well as activity and gene expression of GS were investigated in the outer and inner leaves of lettuce head during storage at 20°C. About two times higher ammonia content out of its initial content was found in the outer leaf portion after the end of 96 h storage period. GS activity in this portion declined to about 27% of the initial level by 24 h of storage, while activity in the inner leaf portion almost unchanged throughout the storage. To understand clearly these biochemical changes, a cDNA encoding GS was isolated, cloned and sequenced from lettuce leaves. The partial cDNA clone referred to as LsGS (Lactuca sativa Glutamine Synthetase; AB440673) consisted of 799 nucleotides which showed more than 80% similarity for both nucleotide and amino acid level with the GS genes of other dicotyledonous plant. Northern blot analysis showed that the level of transcript of GS decreased in the outer-leaf portion after 24 h of storage which well correlates with the enzyme activity of this portion. Although, we found no specific trend in GS activity in the inner-leaf portion, the transcript level gradually increased until the end of storage period. The inconsistency between enzyme activity and gene expression may suggest that GS expression in lettuce is controlled by multiple levels of regulations in a tissue-specific manner.
  Dulal Chandra , Toshiyuki Matsui , Haruo Suzuki and Yusuke Kosugi
  To investigate the effects of low temperature on the physiological and biochemical processes, we held two crisphead lettuce (Lactuca sativa L.) cultivars ‘Shizuka` and ‘Cisco` at 5°C for 10 days. Minimum weight loss and lower respiration rate along with a higher hue angle value were recorded from both cultivars. However, cultivar ‘Cisco` showed higher relative weight loss, respiration rate and accumulation of ammonia compared to that of ‘Shizuka`. Except in the leaf portion of ‘Shizuka`, glutamine synthetase (GS, activity did not change significantly. The accumulation of ammonia was supposed to be below the critical level to repress GS activity. However, the highest amount of ammonia content was found at the end of the storage period in all cases. Amination activity of glutamate dehydrogenase (GDH, decreased by day 4 and slightly increased thereafter while the deamination activity did not show any significant change. Overall, GDH-amination activity was remarkably higher than GDH-deamination activity and the leaf portion showed higher GDH-amination activity while the midrib portion showed higher GDH-deamination activity. Between the two cultivars, ‘Cisco` could have a shorter shelf life than ‘Shizuka`. The results suggested that although the visual quality of lettuce was maintained at low temperature, some physio-biochemical changes occurred in this period.
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