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ISSN 1672-9145                                                Acta Biochim Biophys Sin 2005, 37(6):  406–414                                                  CN 31-1940/Q

Anaerobic Induction of Isocitrate Lyase and Malate Synthase in Submerged Rice Seedlings Indicates the Important Metabolic Role of the Glyoxylate Cycle

Ying LU1,2#, Yong-Rui WU1,2#, and Bin HAN1,3*

 

1 National Center for Gene Research, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China;

2 Graduate School of the Chinese Academy of Sciences, Beijing 100039, China;

3 Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China

 

Abstract        The glyoxylate cycle is a modified form of the tricarboxylic acid cycle that converts C2 compounds into C4 dicarboxylic acids at plant developmental stages. By studying submerged rice seedlings, we revealed the activation of the glyoxylate cycle by identifying the increased transcripts of mRNAs of the genes of isocitrate lyase (ICL) and malate synthase (MS), two characteristic enzymes of the glyoxylate cycle. Northern blot analysis showed that ICL and MS were activated in the prolonged anaerobic environment. The activity assay of pyruvate decarboxylase and ICL in the submerged seedlings indicated an 8.8-fold and 3.5-fold increase over that in the unsubmerged seedlings, respectively. The activity assay of acetyl-coenzyme A synthetase in the submerged seedlings indicated a 3-fold increase over that in the unsubmerged seedlings, which is important for initiating acetate metabolism. Consequently, we concluded that the glyoxylate cycle was involved in acetate metabolism under anaerobic conditions.

 

Key words        Oryza sativa; glyoxylate cycle; isocitrate lyase; malate synthase; acetyl-coenzyme A synthetase; anoxia

 

 

 

 

 

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Received: March 23, 2005        Accepted: April 14, 2005

This work was supported by the grants from the Ministry of Science and Technology of China (No. 2002aa2z1003), the Chinese Academy of Sciences and the Shanghai Municipal Commission of Sciences and Technology (No. 038019315)

# These authors contributed equally to this work

*Corresponding author: Tel: 86-21-64845260; Fax, 86-21-64825775; E-mail, [email protected]