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First published online September 24, 2004; 10.1104/pp.104.044776 Plant Physiology 136:3364-3375 (2004) © 2004 American Society of Plant Biologists Metabolic Profiling of the Sink-to-Source Transition in Developing Leaves of Quaking Aspen1Plant Biotechnology Research Center, School of Forest Resources and Environmental Science (M.L.J., H.J., H.-S.C., C.-J.T., S.A.H), and Department of Mathematical Sciences (H.-S.C.), Michigan Technological University, Houghton, Michigan 49931
Profiles of small polar metabolites from aspen (Populus tremuloides Michx.) leaves spanning the sink-to-source transition zone were compared. Approximately 25% of 250 to 300 routinely resolved peaks were identified, with carbohydrates, organic acids, and amino acids being most abundant. Two-thirds of identified metabolites exhibited greater than 4-fold changes in abundance during leaf ontogeny. In the context of photosynthetic and respiratory measurements, profile data yielded information consistent with expected developmental trends in carbon-heterotrophic and carbon-autotrophic metabolism. Suc concentration increased throughout leaf expansion, while hexose sugar concentrations peaked at mid-expansion and decreased sharply thereafter. Amino acid contents generally decreased during leaf expansion, but an early increase in Phe and a later one in Gly and Ser reflected growing commitments to secondary metabolism and photorespiration, respectively. The assimilation of nitrate and utilization of stored Asn appeared to be marked by sequential changes in malate concentration and Asn transaminase activity. Principal component and hierarchical clustering analysis facilitated the grouping of cell wall maturation (pectins, hemicelluloses, and oxalate) and membrane biogenesis markers in relation to developmental changes in carbon and nitrogen assimilation. Metabolite profiling will facilitate investigation of nitrogen use and cellular development in Populus sp. varying widely in their growth and pattern of carbon allocation during sink-to-source development and in response to stress.
1 This work was supported by the Michigan Life Sciences Corridor Fund of the Michigan Economic Development Corporation (grant no. 085P1000477 to C.-J.T. and S.A.H.). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.044776. * Corresponding author; e-mail sahardin{at}mtu.edu; fax 9064872915. Received April 18, 2004; returned for revision May 27, 2004; accepted May 27, 2004. This article has been cited by other articles:
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