title: Environmental Regulation of Heterosis in the Allopolyploid Arabidopsis suecica.
abstract: Allopolyploids are organisms possessing more than two complete sets of chromosomes from two or more species and are frequently more vigorous than their progenitors. To address the question why allopolyploids display hybrid vigor, we compared the natural allopolyploid Arabidopsis suecica to its progenitor species Arabidopsis thaliana and Arabidopsis arenosa. We measured chlorophyll content, CO2 assimilation, and carbohydrate production under varying light conditions and found that the allopolyploid assimilates more CO2 per unit chlorophyll than either of the two progenitor species in high intensity light. The increased carbon assimilation corresponds with greater starch accumulation, but only in strong light, suggesting that the strength of hybrid vigor is dependent on environmental conditions. In weaker light A. suecica tends to produce as much primary metabolites as the better progenitor. We found that gene expression of LIMIT DEXTRINASE1, a debranching enzyme that cleaves branch points within starch molecules, is at the same level in the allopolyploid as in the maternal progenitor A. thaliana and significantly more expressed than in the paternal progenitor A. arenosa. However, expression differences of β-amylases and GLUCAN-WATER DIKINASE1 were not statistically significantly elevated in the allopolyploid over progenitor expression levels. In contrast to allopolyploids, autopolyploid A. thaliana showed the same photosynthetic rate as diploids, indicating that polyploidization alone is likely not the reason for enhanced vigor in the allopolyploid. Taken together, our data suggest that the magnitude of heterosis in A. suecica is environmentally regulated, arises from more efficient photosynthesis, and, under specific conditions, leads to greater starch accumulation than in its progenitor species.
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Erik M
authors.initials: EM
authors.lastname: Solhaug
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Jacie
authors.initials: J
authors.lastname: Ihinger
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Maria
authors.identifier: 0000-0003-2674-9856
authors.initials: M
authors.lastname: Jost
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Veronica
authors.initials: V
authors.lastname: Gamboa
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Blaine
authors.identifier: 0000-0003-1733-3381
authors.initials: B
authors.lastname: Marchant
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Denise
authors.initials: D
authors.lastname: Bradford
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: R W
authors.initials: RW
authors.lastname: Doerge
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Anand
authors.identifier: 0000-0002-1912-4711
authors.initials: A
authors.lastname: Tyagi
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.).
authors.forename: Amy
authors.identifier: 0000-0002-5880-1308
authors.initials: A
authors.lastname: Replogle
authors.affiliation: Department of Biology, University of Puget Sound, Tacoma, Washington 98416 (E.M.S., J.I., M.J., V.G., B.M., A.T., A.R., A.M.); Sciences Department, Heritage University, Toppenish, Washington 98948 (V.G.); Department of Statistics, Purdue University, West Lafayette, Indiana 47907 (D.B., R.W.D.); and Department of Biology, Fiji National University, Natabua Campus, Lautoka, Fiji (A.T.) amadlung@pugetsound.edu.
authors.forename: Andreas
authors.identifier: 0000-0003-3563-5797
authors.initials: A
authors.lastname: Madlung
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000528:radiation effects; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004777:Environment; D005947:Glucose / Q000378:metabolism; D006823:Hybrid Vigor / Q000235:genetics*; D008027:Light; D010788:Photosynthesis / Q000528:radiation effects; D011123:Polyploidy; D013045:Species Specificity; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002734:Chlorophyll; D002245:Carbon Dioxide; D013395:Sucrose; D002244:Carbon; D013213:Starch; D005947:Glucose; D000077194:Chlorophyll A