Arabidopsis PLDzeta2 regulates vesicle trafficking and is required for auxin response.
Phospholipase D (PLD) and its product, phosphatidic acid (PA), play key roles in cellular processes, including stress and hormonal responses, vesicle trafficking, and cytoskeletal rearrangements. We isolated and functionally characterized Arabidopsis thaliana PLDzeta2, which is expressed in various tissues and enhanced by auxin. A PLDzeta2-defective mutant, pldzeta2, and transgenic plants deficient in PLDzeta2 were less sensitive to auxin, had reduced root gravitropism, and suppressed auxin-dependent hypocotyl elongation at 29 degrees C, whereas transgenic seedlings overexpressing PLDzeta2 showed opposite phenotypes, suggesting that PLDzeta2 positively mediates auxin responses. Studies on the expression of auxin-responsive genes and observation of the beta-glucuronidase (GUS) expression in crosses between pldzeta2 and lines containing DR5-GUS indicated that PLDzeta2, or PA, stimulated auxin responses. Observations of the membrane-selective dye FM4-64 showed suppressed vesicle trafficking under PLDzeta2 deficiency or by treatment with 1-butanol, a PLD-specific inhibitor. By contrast, vesicle trafficking was enhanced by PA or PLDzeta2 overexpression. Analyses of crosses between pldzeta2 and lines containing PIN-FORMED2 (PIN2)-enhanced green fluorescent protein showed that PLDzeta2 deficiency had no effect on the localization of PIN2 but blocked the inhibition of brefeldin A on PIN2 cycling. These results suggest that PLDzeta2 and PA are required for the normal cycling of PIN2-containing vesicles as well as for function in auxin transport and distribution, and hence auxin responses.
Li
Gang
G
National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China.
Xue
Hong-Wei
HW
D020001:1-Butanol / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport / Q000502:physiology; D020126:Brefeldin A / Q000494:pharmacology; D003433:Crosses, Genetic; D005966:Glucuronidase / Q000032:analysis; D018522:Gravitropism; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology*; D026901:Membrane Transport Proteins / Q000032:analysis / Q000378:metabolism; D008969:Molecular Sequence Data; D010712:Phosphatidic Acids / Q000378:metabolism / Q000494:pharmacology; D010739:Phospholipase D / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010937:Plant Growth Regulators / Q000494:pharmacology*; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000254:growth & development; D022161:Transport Vesicles / Q000502:physiology*
D020001:1-Butanol; D029681:Arabidopsis Proteins; D020126:Brefeldin A; D005966:Glucuronidase; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D010712:Phosphatidic Acids; D010739:Phospholipase D; D010937:Plant Growth Regulators; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C510354:phospholipase Dzeta2, Arabidopsis