Suppression of phospholipase Dα1 induces freezing tolerance in Arabidopsis:: Response of coldresponsive genes and osmolyte accumulation

Phospholipase D (PLD; EC 3.1.4.4) plays an important role in membrane lipid hydrolysis and in mediation of plant responses to a wide range of stresses. PLD alpha 1 abrogation through antisense suppression in Arabidopsis thaliana resulted in a significant increase in freezing tolerance of both non-acclimated and cold-acclimated plants. Although non-acclimated PLD alpha 1-deficient plants did not show the activation of cold-responsive C-repeat/dehydration-responsive element binding factors (CBFs) and their target genes (COR47 and COR78), they did accumulate osmolytes to much higher levels than did the non-acclimated wildtype plants. However, a stronger expression of COR47 and COR78 in response to cold acclimation and to especially freezing was observed in PLD alpha 1-deficient plants. Furthermore, a slower activation of CBF1 was observed in response to cold acclimation in these plants compared to the wild-type plants. Typically, cold acclimation resulted in a higher accumulation of osmolytes in PLD alpha 1-deficient plants than in wild-type plants. Inhibition of PLD activity by using lysophosphatidylethanotamine (LPE) also increased freezing tolerance of Arabidopsis, albeit to a lesser extent than did the PLD antisense suppression. Exogenous LPE induced expression of COR15a and COR47 in the absence of cold stimulus. These results suggest that PLD alpha 1 plays a key role in freezing tolerance of Arabidopsis by modulating the cold-responsive genes and accumulation of osmolytes. (c) 2005 Elsevier GmbH. All rights reserved.