Membranes are the primary sites of perception for extracellular stimuli and are rich sources for signaling messengers. Phospholipase D (PLD) hydrolyzes membrane lipids to produce the messenger phosphatidic acid (PA), and the activation of PLD occurs under different hyperosmotic stresses, including dehydration and salt stress. We have recently found that PLDÎ±3 that plays a positive role in hyperosmotic stress. PLDÎ±3 hydrolyzes multiple substrates with distinguishable preferences. The involvement of PLDÎ±3 in hyperosmotic stress is through a different mechanism from that PLDÎ±1, which mediates the effect of abscisic acid on stomatal movements. PLDÎ±3 enhances root growth and accelerates flowering time under hyperosmotic stress. Alterations of PLDÎ±3 affect the level of PA, transcripts of TOR and AGC2.1, ABA-responsive genes, and phosphorylated S6K protein under hyperosmotic stress. Our further observation shows that PLDÎ±3 is also involved in glucose response. PLDÎ±3-KO seeds and seedlings are less sensitive to glucose whereas PLDÎ±3-overepressed seeds are more sensitive than wild type. These results point to a possibility that PLDÎ±3-mediated lipid signaling may play a role in integrating nutrient sensing, protein kinase activation, and hormones responses to regulate growth and development under hyperosmotic stress.
Addendum to: Hong Y, Pan X, Welti R, Wang X. Phospholipase DÎ±3 is involved in the hyperosmotic response in Arabidopsis. Plant Cell 2008; 20:803-16.Full Text Options