title: Phospholipase D alpha 1-derived phosphatidic acid interacts with ABI1 phosphatase 2C and regulates abscisic acid signaling.
abstract: Phospholipase D (PLD) and protein phosphatase 2C (PP2C) both play a role in mediating plant responses to abscisic acid (ABA). In this article, we show that PLD alpha 1 and its product, phosphatidic acid (PA), regulate a PP2C, ABI1, which is a negative regulator of ABA responses in Arabidopsis. Leaves from a T-DNA insertional mutant of PLD alpha 1 and PLD alpha 1-antisense plants lose more water than do wild-type plants. The stomatal closure of PLD alpha 1-null leaves is insensitive to ABA but is promoted by PA. ABA treatment promotes an increase in PA from phosphatidylcholine in wild type but not in PLD alpha 1-null cells. PLD alpha 1-derived PA binds to ABI1; the PA-ABI1 binding is demonstrated by coprecipitating PA with ABI1 from plant cells, measuring binding of PA from vesicles to ABI1, and assaying ABI1 bound to PA immobilized on a filter. Deletion and site-specific mutational analyses show that arginine 73 in ABI1 is essential for PA-ABI1 binding. PA binding decreases the phosphatase activity of ABI1. The lack of ABA-induced production of PA in PLD alpha 1-null cells results in a decrease in the association of ABI1 with the plasma membrane in response to ABA. These results indicate that PA produced by PLD alpha 1 inhibits the function of the negative regulator ABI1, thus promoting ABA signaling. The identification of ABI1 as a direct target of the lipid messenger PA provides a functional link between the two families of important signaling enzymes, PLD and PP2C.
authors.affiliation: Department of Biochemistry, Kansas State University, Manhattan, 66506, USA.
authors.forename: Wenhua
authors.initials: W
authors.lastname: Zhang
authors.forename: Chunbo
authors.initials: C
authors.lastname: Qin
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Xuemin
authors.initials: X
authors.lastname: Wang
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology / Q000502:physiology*; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D007700:Kinetics; D016296:Mutagenesis; D010712:Phosphatidic Acids / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000502:physiology; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology*; D014867:Water / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D010712:Phosphatidic Acids; D010743:Phospholipids; D014867:Water; D000040:Abscisic Acid; C087434:ABI1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D010739:Phospholipase D