Glycine betaine and choline synthesis in maize and sorghum
Abstract
In response to environmental stresses, such as drought and salinity, many plants accumulate compatible solutes to offset the effect of water loss. Glycine betaine (GB) is the most predominant compatible solute accumulated by a wide variety of plants, including maize and sorghum. In an attempt to further characterize the limitations on GB production in plants, near isogenic lines (NILs) of maize and sorghum were studied. Specifically the route of choline (GB precursor) synthesis was examined using radiolabeled precursors. It was found that GB-deficiency in these maize and sorghum lines was due to a block in choline oxidation. Furthermore, it was found that the lack of GB synthesis also led to elevated levels of choline and P-choline in GB-deficient lines. To further examine this finding, the initial choline oxidizing enzyme, choline monooxygenase (CMO) was cloned from a GB-accumulating cDNA library, and its expression in both maize and sorghum was studied. Both sorghum and maize GB-deficient lines were found to express the corresponding CMO gene, and in maize, antibodies were able to detect native CMO proteins in extracts from both GB-accumulating and GB-deficient lines, suggesting that the GB-deficiency may not be due to mutations in the choline oxidizing enzyme. To gain a better understanding of choline synthesis in maize and sorghum, phosphoethanolamine N-methyltransferase (PEAMT) was cloned and examined at the biochemical and transcriptional level.
Degree
Ph.D.
Advisors
Rhodes, Purdue University.
Subject Area
Biochemistry|Plant pathology
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