molecular species was identified in relation to the total number of acyl carbon atoms and double bonds. Changes in both the absolute levels of these lipids, which reflect lipid degradation, and the Peretinoin cost relative levels of these lipids, which can reflect the interconversion among lipids, were visualized using hierarchal clustering analysis.The relative change in the levels of lipids from 0 to 5 days is the percentage value for the significant difference between the values at day 0 and 5 days over the value at day 0. Values in the same row with different letters are significantly different. “”indicates that the value is significantly different from that of the WS under the same condition. Values are means 6 SDs. doi:10.1371/journal.pone.0065687.t001 PLDd-KO leaves following ABA treatment were greater than those between WS and PLDd-KO leaves floated on water. These results suggested 16824511 that ABA treatment affected lipid degradation, and that elimination of PLDd affected lipid degradation during ABA-promoted senescence in particular. Detailed data mining of the changes in membrane lipids and the functional characterization of PLDd during leaf senescence are described below. 6 Suppression of PLDd Retards Leaf Senescence Different Effects of Detachment-induced Senescence on Plastidic and Extraplastidic Lipids molecular species of PG. In Arabidopsis, PG includes four molecular species, namely 34:1 PG, 34:2 PG, 34:3 PG, and 34:4 PG. Whereas 34:4 PG, which harbors a 16:1 acyl chain, is part of the plastidic membrane, both 34:1 PG and 34:2 PG are extraplastidic lipids. Of the two molecules that correspond to 34:3 PG, one contains a 16:1 acyl chain and is part of the plastidic membrane, whereas the other is extraplastidic. During detachment-induced senescence in WS leaves, the decrease in the percentage of 34:4 PG was more than that of 34:3 PG, and the decrease in 34:3 PG was more than that of either 34:2 PG or 34:1 PG combined. In other words, the degradation of PG molecular species in plastidic membranes was significantly greater than that in extraplastidic membranes. These results indicated that most of the dramatic degradation of lipids during detachment-induced senescence occurred in plastids. During detachment-induced senescence, the patterns of changes in membrane lipids were similar in PLDd-KO leaves and WS leaves. There were no differences in lipid levels Suppression of PLDd Retards Leaf Senescence Attenuation of the Decrease in Levels of Plastidic Lipids in PLDd-KO Leaves during ABA-promoted Senescence During ABA-promoted senescence in PLDd-KO leaves, the amount of total lipids declined by 51.5%, which was significantly less than the decrease of 66.1% observed in WS. Levels of MGDG, DGDG, and PG were significantly lower in ABA-treated leaves than in those exposed to water, whereas the levels of PC, PE, PI, PA, and PS were higher than or similar to those in leaves exposed to water. These data indicated that decreases in lipid levels also occurred in PLDd-KO plants, but these decreases occurred only among plastidic lipids during ABA-promoted senescence. In contrast, the levels of MGDG and DGDG were significantly higher in PLDd-KO leaves than in WS leaves. The levels of the plastidic lipids 34:4 PG and 34:3 PG were higher in 17251021 leaves of PLDd-KO plants 
than in leaves of WS. Levels of the extraplastidic lipids 34:2 PG and 34:1 PG in PLDd-KO plants were closer to those in WS. These results indicated that the degradation of plastidic lipids was attenuated
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