Cover illustration: The expression of methyl recycling enzymes in Arabidopsis thaliana. The top image shows the altered morphology of a plant deficient in adenosine kinase (ADK) activity. The central panel presents ADK transcript distribution (dark coloration) in floral meristems of Arabidopsis as detected by in situ hybridization. In most organs such as root, stem and leaves ADK and S-adenosylhomocysteine (SAH) hydrolase are co-ordinately expressed, consistent with their catalysis of succeeding steps in the methylation cycle. The bottom image shows immunodetection of SAH hydrolase (green fluorescence) in the endothelial layer of a maturing Arabidopsis seed. Surprisingly, a corresponding accumulation of ADK was not observed, suggesting that SAH hydrolase has an additional metabolic role, apart from methyl recycling, in seeds. Photographs courtesy of Luiz Pereira.
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