The role of fructan metabolism in adaptation to cold acclimation and grain filling in wheat (Triticum aestivum L.): A metabolic and transcriptomic analysis
Abstract
Wheat (Triticum aestivum L.) accumulates fructans, water soluble oligomers of fructose, in various tissues for diverse purposes. Seedlings of winter wheat accumulate and store fructans in leaf blades and leaf sheaths during cold acclimation. In addition to osmoprotectant, fructan was shown to be a major reserve carbohydrate in stem internodes to supply carbon to grain during the late stage of grain filling when photosynthesis activity in leaves decreased. Several fructan metabolic enzymes have been cloned and their functions characterized. In addition, there are reports that describe correlations between fructan content and the enzyme activity of fructan metabolic enzymes from crude protein extracts that do not account for activities of enzymes with related functions such as invertases. The objectives of this study were to investigate the correlation between fructan structure and fructan metabolic gene expression, changes in water soluble carbohydrates in different stem internodes from diverse wheat cultivars and triticale during stem development, and global gene expression in the stem internode of wheat during fructan biosynthesis and degradation to examine the relationship of genes encoding fructan metabolic enzymes to carbohydrate metabolism and carbon transport. Expression of genes encoding fructan metabolic enzymes was studied in both cold-induced wheat seedlings and field-grown wheat in the reproductive and grain developmental stages. The expression of three characterized fructofuranosyltransferase genes increased during fructan biosynthesis and decreased during fructan degradation. Interestingly, transcripts of two fructan exohydrolases were correlated with fructan biosynthesis enzymes rather than correlated with the other fructan exohydrolases which were involved in fructan degradation. There were significant differences in water soluble carbohydrates in stems among wheat cultivars and triticale which had different morphological and physiological traits. From gene expression analysis using microarray technology, we indicate the importance of sucrose metabolism to regulate fructan biosynthesis and suggest the possibility that a senescence mechanism starts and accelerates fructan degradation in the stem internode of wheat.
Degree
Ph.D.
Advisors
Housley, Purdue University.
Subject Area
Agronomy|Molecular biology|Plant sciences
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