title: Transcriptome Profiling of the Green Alga Spirogyra pratensis (Charophyta) Suggests an Ancestral Role for Ethylene in Cell Wall Metabolism, Photosynthesis, and Abiotic Stress Responses.
abstract: It is well known that ethylene regulates a diverse set of developmental and stress-related processes in angiosperms, yet its roles in early-diverging embryophytes and algae are poorly understood. Recently, it was shown that ethylene functions as a hormone in the charophyte green alga Spirogyra pratensis Since land plants evolved from charophytes, this implies conservation of ethylene as a hormone in green plants for at least 450 million years. However, the physiological role of ethylene in charophyte algae has remained unknown. To gain insight into ethylene responses in Spirogyra, we used mRNA sequencing to measure changes in gene expression over time in Spirogyra filaments in response to an ethylene treatment. Our analyses show that at the transcriptional level, ethylene predominantly regulates three processes in Spirogyra: (1) modification of the cell wall matrix by expansins and xyloglucan endotransglucosylases/hydrolases, (2) down-regulation of chlorophyll biosynthesis and photosynthesis, and (3) activation of abiotic stress responses. We confirmed that the photosynthetic capacity and chlorophyll content were reduced by an ethylene treatment and that several abiotic stress conditions could stimulate cell elongation in an ethylene-dependent manner. We also found that the Spirogyra transcriptome harbors only 10 ethylene-responsive transcription factor (ERF) homologs, several of which are regulated by ethylene. These results provide an initial understanding of the hormonal responses induced by ethylene in Spirogyra and help to reconstruct the role of ethylene in ancestral charophytes prior to the origin of land plants.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, Bioscience Research Building, College Park, Maryland 20742-5815 (B.V.d.P., E.D.C., C.C., C.F.D.); and Laboratory of Functional Plant Biology, Department of Physiology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium (D.V.D.S.).
authors.forename: Bram
authors.identifier: 0000-0001-5638-2472
authors.initials: B
authors.lastname: Van de Poel
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, Bioscience Research Building, College Park, Maryland 20742-5815 (B.V.d.P., E.D.C., C.C., C.F.D.); and Laboratory of Functional Plant Biology, Department of Physiology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium (D.V.D.S.).
authors.forename: Endymion D
authors.identifier: 0000-0002-6186-5628
authors.initials: ED
authors.lastname: Cooper
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, Bioscience Research Building, College Park, Maryland 20742-5815 (B.V.d.P., E.D.C., C.C., C.F.D.); and Laboratory of Functional Plant Biology, Department of Physiology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium (D.V.D.S.).
authors.forename: Dominique
authors.identifier: 0000-0002-7755-1420
authors.initials: D
authors.lastname: Van Der Straeten
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, Bioscience Research Building, College Park, Maryland 20742-5815 (B.V.d.P., E.D.C., C.C., C.F.D.); and Laboratory of Functional Plant Biology, Department of Physiology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium (D.V.D.S.) delwiche@umd.edu carenc@umd.edu.
authors.forename: Caren
authors.identifier: 0000-0003-0384-5888
authors.initials: C
authors.lastname: Chang
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, Bioscience Research Building, College Park, Maryland 20742-5815 (B.V.d.P., E.D.C., C.C., C.F.D.); and Laboratory of Functional Plant Biology, Department of Physiology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium (D.V.D.S.) delwiche@umd.edu carenc@umd.edu.
authors.forename: Charles F
authors.identifier: 0000-0001-7854-8584
authors.initials: CF
authors.lastname: Delwiche
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D002473:Cell Wall / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D016000:Cluster Analysis; D005030:Ethylenes / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling / Q000379:methods*; D063990:Gene Ontology; D008027:Light; D010788:Photosynthesis / Q000187:drug effects* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D058131:Spirogyra / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D013696:Temperature
chemical_list: D020418:Algal Proteins; D005030:Ethylenes; D012965:Sodium Chloride