title: Roles of four Arabidopsis U-box E3 ubiquitin ligases in negative regulation of abscisic acid-mediated drought stress responses.
abstract: AtPUB18 and AtPUB19 are homologous U-box E3 ubiquitin ligases in Arabidopsis (Arabidopsis thaliana). AtPUB19 is a negative regulator of abscisic acid (ABA)-mediated drought responses, whereas the role of AtPUB18 in drought responses is unknown. Here, loss-of-function and overexpression tests identified AtPUB18 as a negative regulator in ABA-mediated stomatal closure and water stress responses. The atpub18-2atpub19-3 double mutant line displayed more sensitivity to ABA and enhanced drought tolerance than each single mutant plant; therefore, AtPUB18 and AtPUB19 are agonistic. Stomatal closure of the atpub18-2atpub19-3 mutant was hypersensitive to hydrogen peroxide (H(2)O(2)) but not to calcium, suggesting that AtPUB18 and AtPUB19 exert negative effects on the ABA signaling pathway downstream of H(2)O(2) and upstream of calcium. AtPUB22 and AtPUB23 are other U-box E3 negative regulators of drought responses. Although atpub22atpub23 was more tolerant to drought stress relative to wild-type plants, its ABA-mediated stomatal movements were highly similar to those of wild-type plants. The atpub18-2atpub19-3atpub22atpub23 quadruple mutant exhibited enhanced tolerance to drought stress as compared with each atpub18-2atpub19-3 and atpub22atpub23 double mutant progeny; however, its stomatal behavior was almost identical to the atpub18-2atpub19-3 double mutant in the presence of ABA, H(2)O(2), and calcium. Overexpression of AtPUB18 and AtPUB19 in atpub22atpub23 effectively hindered ABA-dependent stomatal closure, but overexpression of AtPUB22 and AtPUB23 in atpub18-2atpub19-3 did not inhibit ABA-enhanced stomatal closure, highlighting their ABA-independent roles. Overall, these results suggest that AtPUB18 has a linked function with AtPUB19, but is independent from AtPUB22 and AtPUB23, in negative regulation of ABA-mediated drought stress responses.
authors: Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea.
authors: Dong Hye
authors: DH
authors: Seo
authors: Moon Young
authors: MY
authors: Ryu
authors: Fabien
authors: F
authors: Jammes
authors: Jae Hwan
authors: JH
authors: Hwang
authors: Michelle
authors: M
authors: Turek
authors: Bin Goo
authors: BG
authors: Kang
authors: June M
authors: JM
authors: Kwak
authors: Woo Taek
authors: WT
authors: Kim
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology*; D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002734:Chlorophyll / Q000032:analysis; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005816:Genetic Complementation Test / Q000379:methods; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008353:Mannitol / Q000494:pharmacology; D008969:Molecular Sequence Data; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D054046:Plant Stomata / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction; D013312:Stress, Physiological; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002734:Chlorophyll; D008353:Mannitol; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; D044767:Ubiquitin-Protein Ligases; D002118:Calcium