Three SAC1-like genes show overlapping patterns of expression in Arabidopsis but are remarkably silent during embryo development.
In Saccharomyces cerevisiae, the SAC1 gene encodes a polyphosphoinositide phosphatase (PPIPase) that modulates the levels of phosphoinositides, which are key regulators of a number of signal transduction processes. SAC1p has been implicated in multiple cellular functions: actin cytoskeleton organization, secretory functions, inositol metabolism, ATP transport, and multiple-drug sensitivity. Here, we describe the characterization of three genes in Arabidopsis thaliana, AtSAC1a, AtSAC1b, and AtSAC1c, encoding proteins similar to those of yeast SAC1p. We demonstrated that the three AtSAC1 proteins are functional homologs of the yeast SAC1p because they can rescue the cold-sensitive and inositol auxotroph yeast sac1-null mutant strain. The fact that Arabidopsis and yeast SAC1 genes derived from a common ancestor suggests that this plant multigenic family is involved in the phosphoinositide pathway and in a range of cellular functions similar to those in yeast. Using GFP fusion experiments, we demonstrate that the three AtSAC1 proteins are targeted to the endoplasmic reticulum. Their expression patterns are overlapping, with at least two members expressed in each organ. Remarkably, AtSAC1 genes are not expressed during seed development, and therefore additional phosphatases are required to control phosphoinositide levels in seeds.
Despres
Barbara
B
Laboratoire Génome et Développement des Plantes, UMR CNRS 5096, Université de Perpignan, 52 Avenue de Villeneuve, France.
Bouissonnié
Fabrice
F
Wu
Hui-Ju
HJ
Gomord
Véronique
V
Guilleminot
Jocelyne
J
Grellet
Françoise
F
Berger
Frédéric
F
Delseny
Michel
M
Devic
Martine
M
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002874:Chromosome Mapping; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012639:Seeds / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction / Q000235:genetics
D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D010744:Phosphoric Monoester Hydrolases; D011993:Recombinant Fusion Proteins; C475775:SAC1a protein, Arabidopsis; C475776:SAC1b protein, Arabidopsis; C475777:RHD4 protein, Arabidopsis