Submitted to: Lipids Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2005
Publication Date: 7/22/2005
Citation: Wanjie, S.W., Welti, R., Moreau, R.A., Chapman, K.D. 2005. Identification and quantification of lipid metabolites in cotton fibers: reconciliation with metabolic pathway predictions from dna databases. Lipids Journal. V. 40, No. 8, p.773-785. Interpretive Summary: Cotton fiber is an important agricultural product. Cotton fiber is produced by extremely long single cells, over an inch long, during a period of about 25 days. This period of rapid cellular elongation requires substantial synthesis of macromolecules, including lipids necessary for the developing vacuoles and plasma membranes. Recent technological advances have now made it possible to very accurately measure hundreds of individual molecular species of cellular lipids in these cells (the lipidome) and to measure the thousands of genes in these cells (the genome). This manuscript is the first one to correlate the dynamics of the changes in the lipidome and the genome. The results may identify small genetic changes that could increase the quantity and quality of cotton fibers produced by cotton plants during this narrow stage of plant development.
Technical Abstract: The lipid profiles of cotton fiber cells were determined from total lipid extracts of elongating and maturing cotton fiber cells to see if the membrane lipid composition changed during the phases of rapid cell elongation or secondary cell wall thickening. Total fatty acid content increased during elongation and decreased, thereafter, likely reflecting the assembly of the expanding cell membranes during elongation and the shift to membrane maintenance (and increase in secondary cell wall content) in maturing fibers. Analysis of lipid extracts by electrospray ionization and tandem mass spectrometry (ESI-MS/MS) revealed that in elongating fiber cells (7-10 days post anthesis), the polar lipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE),phosphatidylinositol (PI), phosphatidic acid (PA), phosphatidylglycerol (PG), monogalactosyldiacylglycerol (MGDG), digalactosyl diacylglycerol (DGDG) phosphatidylglycerol (PG) were most abundant. These same glycerolipids were found in similar proportions in maturing fiber cells (21 dpa). Detailed molecular species profiles were determined by ESI-MS/MS for all glycerolipid classes, and ESI-MS/MS results were consistent with lipid profiles determined by HPLC and evaporative light scattering detection (ELSD). The predominant molecular species of PC,PE, PI and PA was 34:3 (16:0, 18:3), while 36:6 (18:3,18:3), also was prevalent. Total fatty acid analysis of cotton lipids confirmed that indeed linolenic (18:3) and palmitic (16:0) acids were the most abundant fatty acids in these cell types. Bioinformatics data were mined from cotton fiber EST databases in an attempt to reconcile expression of lipid metabolic enzymes with lipid metabolite data. Together these data form a foundation for future studies of the functional contribution of lipid metabolism to the development of this unusual and economically important cell type.