JXB Advance Access originally published online on February 1, 2007
Journal of Experimental Botany 2007 58(5):1083-1098; doi:10.1093/jxb/erl275
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RESEARCH PAPER |
Methyl recycling activities are co-ordinately regulated during plant development
1Department of Biology, University of Waterloo, Waterloo, ON, Canada N2L 3G1
2Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
3Department of Biology, Trent University, Peterborough, ON, Canada K9J 7B8
To whom correspondence should be addressed. E-mail: moffatt{at}sciborg.uwaterloo.ca
A large number of compounds including lignin, phospholipids, pectin, DNA, mRNA, and proteins require methyl groups for their functionality. A detailed study of the expression and activities of two enzymes, adenosine kinase (ADK) and S-adenosylhomocysteine hydrolase (SAHH), which are both required for the maintenance and recycling of S-adenosylmethionine-dependent methylation in plants, was carried out. The abundance and tissue localization of ADK and SAHH transcripts and protein were monitored along with their enzyme activities in leaves, stems, buds, siliques, and roots of Arabidopsis. In all but roots and seed coats, the transcript abundance of ADK and SAHH fluctuated co-ordinately, matching changes in their protein and enzyme activities. To evaluate whether this expression pattern was associated with methyl recycling, the protein content and distribution of S-adenosylmethionine synthetase and phosphoethanolamine N-methyltransferase, a key methyltransferase involved in phospholipid synthesis, were investigated. These were found to accumulate in a pattern similar to ADK and SAHH. ADK and SAHH protein and transcript amounts were shown to fluctuate similarly in tissues accumulating lignin. Additionally, the amounts of ADK and SAHH mRNAs were also found at high levels in inflorescence meristems likely to support their higher rates of cell division. Thus, the results point to a co-ordinated and probably transcriptional regulation of these genes in most organs of Arabidopsis; SAHH abundance is distinctly higher in seeds and roots which suggests it may have a non-methyl-related role in these organs.
Key words: Adenosine kinase, S-adenosylhomocysteine hydrolase, S-adenosylmethionine, Arabidopsis, cytokinin metabolism, methyl recycling, seed development
* Present address: Department of Botany, University of Brasilia, L2 Norte, Campus Darcy Ribeiro, Brasilia, DF-70910-900, Brazil.
Present address: Department of Experimental Medicine, McGill University, Montreal, QC, Canada H3A 1A3.
Present address: Department of Cell Biology, The University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd, BMSB 781, Oklahoma City, OK 73104, USA.
Received 25 August 2006; Revised 12 November 2006 Accepted 15 November 2006
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