The control cells contained organelles, nuclei and chromatin with normal morphologies

abolism in senescing membranes by producing PA, which destabilizes membranes and activates other lipid-degrading enzymes, resulting in the loss of both membrane integrity and functionality of membrane-associated proteins. However, there is no direct evidence that PLDa1 produces PA and affects lipid composition during leaf senescence. It remains to be established whether and how any PLD isoforms apart from PLDa1 function in leaf senescence. For example, the role of PLDd, which is one of the two most abundant PLDs, remains to be investigated. Disruption of the structural and functional integrity of cellular membranes is a major factor that contributes to senescence. The disruption of membranes results primarily from the remarkable metabolism of membrane lipids. Loss of membrane phospholipids was observed during natural and ethylene-induced Digitoxin chemical information senescence of cut carnation flowers. Changes in the metabolic relationships among phospholipids, and between galactolipids and phospholipids, have been reported to occur during senescence-associated lipid breakdown. Both the natural senescence of rose petals and dark-induced senescence of cabbage leaves were found to be associated with an overall decrease in levels of membrane phospholipids, with no changes in their relative abundance. Levels of both extraplastidic and plastidic lipids decreased during the natural senescence of tobacco leaves. During dark-induced senescence of barley leaves, decreased levels of galactolipids, monogalactosyldiacylglycerol, and digalactosyldiacylglycerol were accompanied by a transient accumulation of phosphatidylcholine, a major phospholipid. Degradation of the chloroplast membrane occurs early in the ordered series of events that occur in senescing cells. It was suggested that the metabolism of plastidic lipids occurs before that of lipids in the plasma membrane. However, many questions related to the lipid metabolism of senescing leaves have yet to be answered. For example, how does the profile of membrane lipids change during the process Does hormone-promoted senescence affect lipid metabolism, and what are the mechanisms involved Can attenuation of lipid metabolism delay leaf senescence 15864271 In the study reported herein, we describe the alteration of ABApromoted senescence by the application of PLD inhibitors, changes in the expression of PLDd, and the phenotypes of Arabidopsis leaves in which PLDd has been suppressed during senescence. Lipidomic analysis based on electrospray tandem mass spectrometry enabled comparative profiling of 125 molecular species of eight membrane lipid classes in wildtype Arabidopsis and Arabidopsis plants without PLDd 10914735 before and after detachment-induced and ABA-promoted senescence. Detailed analysis of the changes in molecular lipid species revealed the functions of PLDd in ABA-promoted senescence. We also compared PLDa1- and PLDd-mediated formation of PA during ABA-promoted senescence. We propose a model that describes the roles of PLDa1 and PLDd in the retardation of ABA-promoted senescence. Materials and Methods Plant Materials, Growth Conditions, and Phytohormone Treatments Previous studies reported the generation of a PLDd -knockout mutant and PLDd-complemented plants in the background of the Arabidopsis Wassilewskija ecotype, as well as the production of a line, PLDa1-antisense, that was derived from the Arabidopsis ecotype Columbia and in which PLDa1 activity was attenuated by antisense-mediated suppression. Arabidopsis genotypes were gr