Antisense suppression of phospholipase D alpha retards abscisic acid- and ethylene-promoted senescence of postharvest Arabidopsis leaves
1997
Fan, L. | Zheng, S.Q. | Wang, X.M.
Membrane disruption has been proposed to be a key event in plant senescence, and phospholipase D (PLD; EC 3.1.4.4) has been thought to play an important role in membrane deterioration. We recently cloned and biochemically characterized three different PLDs from Arabidopsis. In this study, we investigated the role of the most prevalent phospholipid-hydrolyzing enzyme, PLDalpha, in membrane degradation and senescence in Arabidopsis. The expression of PLDalpha was suppressed by introducing a PLDalpha antisense cDNA fragment into Arabidopsis. When incubated with abscisic acid and ethylene, leaves detached from the PLDalpha-deficient transgenic plants showed a slower rate of senescence than did those from wild-type and transgenic control plants. The retardation of senescence was demonstrated by delayed leaf yellowing, lower ion leakage, greater photosynthetic activity, and higher content of chlohphyll and phospholipids in the PLDalpha antisense leaves than in those of the wild type. Treatment of detached leaves with abscisic acid and ethylene stimulated PLDalpha expression, as indicated by increases in PLDalpha mRNA, protein, and activity. In the absence of abscisic acid and ethylene, however, detached leaves from the PLDalpha-deficient and wild-type plants showed a similar rate of senescence. In addition, the suppression of PLDalpha did not alter natural plant growth and development. These data suggest that PLDalpha is an important mediator in phytohormone-promoted senescence in detached leaves but is not a direct promoter of natural senescence. The physiological relevance of these findings is discussed.
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